The Journal for Equine Nutrition - Autumn '22

autumn wInter 2022 Issue The Journal for 6 Equine Nutrition Equine gastric disease Tania Sundra, BSc (Hons), BVMS, MANZCVS & David Rendle, BVSc, MVM CertEM(IntMed), DipECEIM, FRCVS, RCVS atypical myopathy Anouk Frieling, MSc, BSc (Hons) nutritional support for ppid Dr. Stephanie Wood the importance of respiratory health Anouk Frieling, MSc, BSc (Hons) Moulds and mycotoxins in forages for horses Dr. Cecilia Müller INDUSTRY UPDATE: BIOSECURITY IN EQUINE PREMISES Alan Creighton, BSc (Hons) sleeping patterns in horses Anouk Frieling, MSc, BSc (Hons) PB 1The Journal for Equine Nutrition is FREE. To get every edition of The JEN to your inbox for free, sign up today at feedmark.com/JEN You will receive no marketing literature, and you will be the first to receive The JEN! Editor Contact us Dr Stephanie Wood 01986 782368 [email protected] [email protected] Published by Contributors Feedmark Ltd, Harleston, Norfolk, IP20 0NY With special thanks to Alan Creighton, Anouk Frieling, Cecilia E. Müller, David Rendle and Tania Sundra Whilst every care has been taken in compiling this publication The JEN shall not be made liable for any inaccuracies therein. Production & Design The opinions expressed in this publication are not necessarily Gemma Hill [email protected] those of the Editor/Publisher. 2 3Welcome Welcome to the autumn/winter issue of the JEN. There is number of disease cases. This is followed by the final article still enough daylight to ride in the evenings if you are quick in our metabolic series which focuses on providing Nutritional and the very wet and cold weather of winter is yet to arrive. support for pituitary pars intermedia dysfunction written by This is often a time when management and feeding routines myself. PPID is a complicated disease that can be extremely change to account for reduced grass intake in the coming challenging, and although feeding recommendations align to months, however many of you have needed to feed forage over those previously provided for EMS and laminitis, I felt it was the summer to supplement grass intake due to parched fields. important to confirm them for equids with PPID. Although this was an extra expense at a time when feeding costs The next three articles focus on hygiene and its relationship are normally reduced, feeding forage over summer will make to horse health. Anouk Frieling reviews the importance of the transition to higher forage intakes in the autumn and winter Respiratory health whilst Dr Cecilia Müller from Uppsala safer as your horses will already be adapted to processing high University in Sweden discusses Moulds and mycotoxins in fibre feedstuffs. forages for horses. The different moulds and their impact on health are explained, as are measures you can take to reduce Many horses spend more time stabled in autumn and the likelihood of moulds developing. Alan Creighton, Head winter. During this time owners want to support their horses' of Environment and Nutrition at the Irish Equine Centre, digestive health by ensuring they can continue to eat for the R provides an Industry update on how to achieve high standards majority of the day and spend only short periods without food. EPA of Biosecurity and reduce your horse’s exposure to harmful The importance of trickle feeding and an appropriate diet for P irritants and toxins. gastric health is discussed in the Equine Gastric Disease article DEL written by Tania Sundra of Avon Ridge Equine Veterinary C Anouk Frieling writes the final article of this issue, providing Y Service, Australia, and David Rendle, European Specialise in C an update on what we know so far about Sleeping patterns in E Equine Internal Medicine. Disease causes, risks factors and R horses. This is an emerging area of equine research although % management are all discussed, providing a timely and important 0 our knowledge is increasing, particularly how sleep impacts 01 update on current knowledge and recommendations. Atypical on welfare and performance. As our horses spend more time N Myopathy is a disease with increased prevalence in autumn O in stables over autumn and winter, I know this article will be of therefore Anouk Frieling, Feedmark’s Senior Nutritionist, DE interest to many of you. T reviews our understanding of this debilitating condition. It will NI I hope you enjoy this latest issue of the JEN and can use the be interesting to see how the very high temperatures and dry RP information and recommendations to keep your horses happy conditions many areas have experienced this year will influence and healthy. sycamore seed development, toxin levels and ultimately Dr. Stephanie Wood Editor CONTENTS 4 25 Equine gastric disease Moulds and mycotoxins in forages for horses 10 29 Atypical myopathy Industry update: Biosecurity in equine premises 14 33 Nutritional support for pituitary pars Sleeping patterns in horses intermedia dysfunction 38 20 Glossary The importance of respiratory health 2 3Equine gastric disease Tania Sundra, BSc (Hons), BVMS, MANZCVS (Equine Medicine) David Rendle, BVSc, MVM, CertEM(IntMed), DipECEIM, FRCVS, RCVS and European Specialist in Equine Internal Medicine INTRODUCTION remains the cornerstone of treatment for both diseases. Oral The term equine gastric ulcer syndrome (EGUS) was omeprazole is the only proton-pump inhibitor registered for previously used to describe squamous gastric disease and the treatment of squamous disease, however, it is no longer glandular gastric disease (Sykes et al., 2015a) (Figure considered effective for the treatment of glandular disease 1). More recently however, there has been a growing (Sykes et al., 2015a; Rendle et al., 2018). Following recent appreciation of the differences between both these diseases trends in human medicine, other alternatives are being with a realisation that the pathophysiology, risk factors, explored for both the management of glandular disease, and treatment and management of squamous disease cannot be to improve healing rates for squamous disease. However, extrapolated to glandular disease. Whilst both conditions implementing management changes to reduce risk factors may occur concurrently, it does not necessarily mean there should be initiated alongside drugs to help improve healing is an association between them. rates and to prevent recurrence of disease when treatment is completed. Acid suppressive therapy using proton-pump inhibitors EQUINE SQUAMOUS GASTRIC DISEASE RISK FACTORS AND MANAGEMENT Squamous gastric disease primarily occurs as a result of acid injury to a tissue that has limited defence against a low pH environment. Any disruption to the normal stratification of gastric pH will therefore increase the risk of squamous disease. Excessive exposure to acid causes the stratified squamous epithelium to become thickened and hyperkeratotic. Continued acid exposure leads to sloughing of the superficial epithelium which can progress to deeper lesions and areas of erosion and ulceration (Martineau et al., 2009) (Figure 2). Diet and exercise have consistently been shown to play a major role in the development of squamous disease (Murray & Eichorn, 1996; Vatistas et al., 1999; Begg & O’Sullivan, 2003; Bell et al., 2007; Luthersson et al., 2009). In horses prone to squamous disease, grain feeding should be eliminated from the diet to reduce the production Figure 1. A postmortem specimen of the equine stomach depicting the anatomical regions of the stomach (Sykes et al., 2015). of volatile fatty acids (Luthersson et al., 2009). For horses Reprinted from Journal of Veterinary Internal Medicine, 5. Sykes, B.W., in heavy work, or those that require additional calories, oils Hewetson, M., Hepburn, R.J., Luthersson, N., & Tamzali, Y., 1288-1299. provide a safer alternative to cereals. In a study conducted (Copyright 2015), with permission from John Wiley and Sons. 4 52002). Feeding a small amount (2-3L) of roughage prior to exercise to prevent this acid ‘splash’ would therefore seem logical to reduce the risk of squamous. As the duration of acid exposure also parallels the risk for development of squamous disease (Murray et al., 1996), horses prone to squamous disease should ideally be trained with short duration, high intensity exercise programmes. Environmental factors have also been demonstrated to play a role in the development of squamous disease. Horses Figure 2. Grade 2 squamous disease on the lesser curvature of the are herd animals and direct contact with others appears to stomach. Credit: T. Sundra. reduce the risk of squamous (Lester et al., 2008). A rural in ponies, corn oil supplementation (45ml/day for 5 setting and access to pasture also reduce risk (Lester et weeks) was beneficial to gastric health and was shown to al., 2008). decrease gastric acid production and increase prostaglandin In cases where risk factors are persistent (e.g. racehorses production (Cargile et al., 2004). Maize (corn), vegetable or in training), the prophylactic use of oral omeprazole R canola oil can all be used at up to 1 ml/kg body weight per EP should be considered. A 2019 meta-analysis demonstrated A day. Oil should be gradually introduced over a few weeks P that omeprazole prevented squamous disease in horses D to allow the horse’s metabolism to adapt. Horses should EL in training with only 23% of treated horses developing C receive supplementation with vitamin E (2000 iu/day) YC squamous disease, compared to 77% which were given no E when feeding oil, to mitigate the potential for oxidative R omeprazole prophylaxis (Mason et al., 2019). % injury due to increased free radical production. 001 TREATMENT OPTIONS Feed deprivation has also been shown to cause an N Oral omeprazole is the only registered treatment for O increase in gastric acidity, a reduction in intraluminal D squamous disease and in early studies resulted in 70-77% ET pH and the development of squamous disease (Murray N healing of squamous lesions in racehorses in training IR & Eichorn, 1996). A study conducted on racehorses in P (Murray et al., 1997; Andrews et al., 1999; Doucet et Australia demonstrated that those with free access to al., 2003; Lester et al., 2005). There has been a growing pasture were 3 times less likely to have squamous disease appreciation of the influence of diet and compliance on the (Lester et al., 2008). A 2015 consensus statement (Sykes et efficacy of oral omeprazole (Sykes, 2019). The absorption al., 2015a) also recommended free access to good quality of omeprazole is affected by feeding and administration grass pasture or frequent feeding of hay (4-6 meals/day) to on an empty stomach improves bioavailability (Sykes help restore the normal stratification of gastric pH. In one et al., 2015c). Omeprazole treatment should therefore study, feeding straw as the sole roughage source increased be administered after an overnight fast, 1-2 hours prior the prevalence of squamous disease (Luthersson et al., to feeding. 2009), however a recent study indicated that a 50% straw Esomeprazole has attracted particular interest in human, diet would not cause gastric ulcers to develop (Jansson et and more recently equine medicine as it is absorbed more al., 2021). consistently and metabolised more slowly than omeprazole Exercise causes gastric compression, disruption to the (Andersson et al., 2001). Compared to an equivalent dose stratification of gastric pH and ‘splashing’ of acidic fluid of omeprazole, esomeprazole results in a more pronounced onto the squamous mucosa (Lorenzo-Figueras & Merritt, and consistent acid suppressive effects in man (Lind 4 5hydrochloric acid. The pathogenesis of glandular disease is poorly understood but it has been hypothesised that failure of normal defence mechanisms may predispose the glandular mucosa to injury (Rendle et al., 2018) (Figure 3). We now know that how we manage squamous disease cannot simply be applied to the management of glandular disease. In recent years, a growing body of evidence has Figure 3. An example of equine glandular gastric disease lesions at the indicated that both physiological and psychological stress pylorus. Credit: T. Sundra. may play a role in the development of glandular disease et al., 2000; Rohss et al., 2000; Rohss et al., 2001) and (Malmkvist et al., 2012; Scheidegger et al., 2017; Pedersen similar benefits have now been demonstrated in horses et al., 2018; Sykes et al., 2019). Frequency of exercise (Sykes et al., 2017b). Esomeprazole may therefore offer has been demonstrated to be an important risk factor; advantages over omeprazole and may be more effective the risk of glandular disease was shown to increase 10- for both treatment and prevention of squamous disease, fold in Thoroughbreds exercised more than 5 days per particularly in racehorses where failure rates for treatment week (Sykes et al., 2019). Another study in Canadian and prevention with omeprazole may be 30% and 20% showjumpers found a 5-fold increase in risk of disease in respectively (Sykes et al., 2015a; Mason et al., 2019). horses exercised more than 6 times per week (Pedersen et al., 2018). It has been postulated that the frequency of The highest rates of squamous healing are reported exercise may negatively impact gastric blood flow, thereby following the administration of an unregistered long-acting impairing the normal protective mechanisms of the gastric injectable omeprazole (LAIO) preparation. Intramuscular mucosa. There is evidence that limiting exercise to up to injection overcomes any issues with bioavailability or owner 5 days per week may reduce the risk of glandular disease compliance with the administration of oral preparations. (Rendle et al., 2018). Administration of a LAIO preparation to 6 horses Trainer has been identified as a risk factor for the demonstrated the capacity of the injectable preparation to development of glandular disease in Thoroughbreds (Sykes supress acid more profoundly and consistently than when et al., 2019) and in a riding horse population having a the same horses were administered oral omeprazole every greater number of handlers and riders was associated with day (Sykes et al., 2017a). In the treatment of squamous a greater risk of disease (Mönki et al., 2016). Measures to disease in racehorses in Australia, 100% healing was minimise stress should be tailored to each individual as reported with LAIO after only 2 injections one week apart the effectiveness of specific interventions will vary widely (Sykes et al., 2017a). In a retrospective study performed in between horses. the UK, 93% healing of squamous lesions was observed with 4 weekly injections of LAIO, with most cases having Mucosal protectants such as pectin and lecithin healed within 2 weeks after only 2 injections (Gough complexes may be beneficial in the prevention of glandular et al., 2020). disease (Sykes et al., 2013; Rendle et al., 2018). Lecithin GLANDULAR DISEASE is a phospholipid and pectins are highly viscous substances which may aid to stabilise the protective mucus layer RISK FACTORS AND MANAGEMENT (Sykes et al., 2013) of the glandular mucosa, however Unlike the squamous mucosa, the glandular epithelium has several mechanisms to protect it from injury by robust clinical trials to prove their efficacy are lacking. 6 7Like squamous disease, the highest rates of healing of TREATMENT OPTIONS glandular disease have been reported following the use There are currently no medications registered for the of LAIO (Sykes et al., 2017a; Gough et al., 2022). LAIO treatment of glandular disease and oral omeprazole is also overcomes compliance and bioavailability issues that considered ineffective (Rendle et al., 2018) with healing in is associated the administration of daily, oral medications less than 50% of cases being reported (Sykes et al., 2014). (Sykes et al., 2015c; Rendle et al., 2018). After 2 weeks Whilst acid injury is not thought to initiate glandular, of treatment with LAIO, 9 of 12 horses were reported to a low pH may perpetuate mucosal injury and prevent have healed in a study of racing Thoroughbreds (Sykes healing (Sykes et al., 2015a). As a result, acid suppression et al., 2017a). In a retrospective study in the UK, rates of remains the cornerstone of therapy for glandular disease glandular disease healing after 4 weeks of treatment were and a number of different options including omeprazole 82% with LAIO compared to 50% with oral omeprazole and sucralfate combination, LAIO, esomeprazole or (Gough et al., 2022) misoprostol are currently being utilised. Esomeprazole is being used with increasing frequency Oral omeprazole and sucralfate in combination has been in equine practice as a first-line treatment for horses with reported to result in glandular healing rates of between glandular disease (Sundra, 2021) and to facilitate healing 20-71% (Hepburn & Proudman, 2014; Varley et al., 2019; RE of both squamous and glandular lesions which failed to Barton, et al., 2021). In some populations the response to this PAP respond to oral omeprazole (Rendle, 2017). combination is disappointing and the combination may also DEL present practical challenges regarding the administration of Misoprostol has been reported to result in healing of CY both medications at different times on an empty stomach as C glandular in 55-72% cases (Varley et al., 2019; Pickles ER the absorption of oral omeprazole may be affected both by et al., 2020), however in one report 42% of cases treated %0 feeding and the administration of sucralfate (Sykes et al., 0 with misoprostol, squamous disease either developed or 1 N 2015c; Sykes, 2019) worsened (Pickles et al., 2020). There are significant human O DETNIRP David Rendle, BVSc, MVM, CertEM(IntMed), DipECEIM, FRCVS, RCVS and European Specialist in Equine Internal Medicine Following graduation from the University of Bristol in 2001, David worked in farm animal and equine practice before completing an internship at Liphook Equine Hospital. David spent a number of years at Liphook Equine Hospital before moving to Rainbow Equine Hospital in Yorkshire, where he became a director and subsequently a clinical director. After 5 years in Yorkshire David returned to his roots and now lives on the edge of Exmoor, combining veterinary activities with upland sheep farming. David now works as an independent equine medicine and therapeutics consultant, is actively involved in clinical research and sees referral cases by request. In 2019, David was made a Fellow of the Royal College of Veterinary Surgeons in recognition of his contribution to clinical practice. He is President-elect of the British Equine Veterinary Association and is Chair of their health and medicines committee. 6 7and there should be a focus on minimising stressors. Acid- health and safety concerns with the use of misoprostol and suppressive medications remain the cornerstone of therapy it needs to be handled very carefully. for both squamous and glandular disease. Whilst oral SUMMARY omeprazole has been proven effective for the management Optimising diet and management are fundamental to of squamous disease it is largely ineffective for the the prevention and management of gastric disease. Careful treatment of glandular disease. New (mostly unregistered) consideration should be given to the constituents of the alternatives are being explored and show promise in improving healing rates of both conditions. diet, the timing and frequency of feeding, exercise routines Tania Sundra, BSc (Hons), BVMS, MANZCVS (Equine Medicine) Tania graduated from Murdoch University in 2009 and completed an equine internship at a busy performance horse hospital in the USA. Upon returning home she spent a few years working in racetrack and reproduction clinics in Western Australia. In 2015, Tania founded Avon Ridge Equine Veterinary Services – an ambulatory equine practice servicing Perth and surrounding regions. In 2019, she successfully completed examinations to become a member of the Australian & New Zealand College of Veterinary Scientists, Equine Medicine chapter. Tania has a keen interest in all things related to equine medicine, particularly gastroenterology, endocrinology and parasitology. Do YOU have anything you would like our Scientists to research? If you have any specific topics that you would like us to feature in The JEN, please email us at: [email protected] 8 9REFERENCES Andersson, T., Rohss, K., Bredberg, E. & Hassan-Alin, M. (2001). Pharmacokinetics and pharmacodynamics of esomeprazole, the S-isomer of omeprazole. Alimentary Pharmacology and Therapeutics, 15(10): 1563– 1569. doi:10.1046/j.1365-2036.2001.01087.x. Andrews, F.M., Sifferman, R.L., Bernard, W., Hughes, F.E., Holste, J.E., Daurio, C.P., Alva, R. & Cox, J.L. (1999). Efficacy of omeprazole paste in the treatment and prevention of gastric ulcers in horses. Equine Veterinary Journal. Supplement, 31(S29): 81-86. Barton, A., Merle, R. & Gehlen, H. (2021). Efficacy of two oral omeprazole formulations for the therapy of equine gastric ulcer disease. In: Proceedings of the European College of Equine Internal Medicine Congress. Begg, L.M. & O’Sullivan, C.B. (2003). 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The effect of feeding on the pharmacokinetic variables of two commercially available formulations of omeprazole. Journal of Veterinary Pharmacology and Therapeutics, 38(5): 500-503. doi:10.1111/jvp.12210. Sykes, B.W., Underwood, C. & Mills, P.C. (2017b). The effects of dose and diet on the pharmacodynamics of esomeprazole in the horse. Equine Veterinary Journal, 49(5): 637–642. doi:10.1111/evj.12670. Varley, G., Bowen, I.M., Habershon‐Butcher, J.L., Nicholls, V. & Hallowell, G.D. (2019). Misoprostol is superior to combined omeprazole‐sucralfate for the treatment of equine gastric glandular disease. Equine Veterinary Journal, 51(5): 575–580. doi:10.1111/evj.13087. Vatistas, N., Snyder, J., Carlson, G., Johnson, B., Arthu, R., Thurmond, M., Zhou, H. & Lloyds, K.L.K. (1999). Cross‐sectional study of gastric ulcers of the squamous mucosa in Thoroughbred racehorses. Equine Veterinary Journal, 31(S29): 34–39. doi:10.1111/j.2042-3306.1999.tb05166.x. 8 9Atypical myopathy Anouk Frieling, MSc Equine Sciences, BSc (Hons) Atypical myopathy (AM) is a seasonal, non-exercise the seeds over sprouts or that due to the better quality of related, disease causing acute rhabdomyolysis (rapid spring grass horses do not feel the need to search for other breakdown of damaged muscle tissue) which affects feedstuff when out on pasture (Westermann et al., 2016). the muscles of the horse (Votion & Serteyn, 2008). Currently, it is unknown why the number of affected horses Atypical means that it is an unusual disease which occurs differs annually, but it is suggested that it is influenced by sporadically and therefore does not fit into a diagnostic factors that have an effect on the number of sycamore seeds category. Through recent years research has been dedicated on pasture such as a change in climate or tree maturity to finding possible causes that trigger the sudden onset of (Herrera et al., 1998; González-Medina et al., 2017). AM to be able to prevent AM or recognise the early signs of this highly fatal disease (Votion et al., 2007). The disease is most commonly seen in grazing horses during autumn but occasionally also occurs during other seasons (González- Medina et al., 2017). This article will review current information about the cause of this disease, the clinical signs, treatment and prevention. CAUSES AND PATHOPHYSIOLOGY Equine AM mainly affects the respiratory muscles and muscles that support the skeleton and maintain balance (Żuraw et al., 2016). Possible causes of AM in horses that Figure 1. During autumn the seeds from the sycamore tree fall on the have been identified so far are virus infections, bacterial pasture on which horses graze. These seeds can be toxic and horses ingesting these seeds can develop atypical myopathy. or fungal toxins, plant toxins and nutritional deficiencies (Harris & Whitwell, 1990; Brandt et al., 1997). One of the After ingestion, HGA interferes with metabolic most common causes of the sudden onset of clinical signs processes (Karlíková et al., 2016), and causes multiple of AM is related to the ingestion of sycamore seeds (Figure acyl-CoA dehydrogenase deficiency (MADD) which is 1), leaves or sprouts which contain the toxin hypoglycin A a form of rhabdomyolysis in horses (González-Medina (HGA) (Fabius & Westermann, 2018). Westermann et al. et al., 2021). To date, the complete pathophysiology of (2016) suggested that the ingestion of a kilogram of sprouts AM is unknown but research in AM affected horses, and of the sycamore tree is more dangerous in comparison to other animal and human studies with similar diseases, a kilogram of sycamore seeds. Interestingly, during spring have given some insight into the pathophysiology of this there are more sprouts available and during autumn more disease (Karlíková et al., 2016). Studies analysing the seeds are available (Westermann et al., 2016). The number muscles of affected horses have found that the degenerative of affected horses differs per year, but as mentioned, most process of AM mainly affects type I muscle fibres and horses are affected by the disease during autumn when the has a lesser effect on type II muscle fibres (Cassart et al., 2007; Palencia & Rivero, 2007). In the affected type I sycamore seeds are present on pasture (Unger et al., 2014; muscle fibres an increased lipid storage has been registered Żuraw et al., 2016). This could imply that horses prefer 10 11which might imply that metabolism is compromised due appetite loss or in some cases increased appetite (Votion to AM (Brandt et al., 1997; Votion, 2012). Type I muscle & Serteyn, 2008). Measurable signs in horses affected by fibres are slow contracting muscle fibres depending on AM are elevated lactate dehydrogenase (LDH) and creatine aerobic respiration (require oxygen), whilst type 2 are kinase (CK) which indicates tissue damage (Bochnia et al., quick contracting fibres which are dependent on anaerobic 2015). The toxin HGA from the ingested sycamore seeds respiration (without oxygen). A commonly accepted theory can be measured using blood and urine samples. Horses about AM is that after HGA intoxication the Coenzyme affected by AM can also experience electrolyte imbalances A of methylenecyclopropyl acetic acid, a metabolite (Votion, 2012). of HGA, inhibits flavin adenine dinucleotide (FAD), a coenzyme associated with various proteins, and acyl-CoA dehydrogenases in the body (Karlíková et al., 2016). Type I muscle fibres derive energy from fatty acid metabolism in muscle cells, but the inhibition of mitochondrial enzymes influences this metabolism resulting in lipid accumulation, meaning there is no energy available for Type I muscle fibres (Westermann et al., 2008; Lemieux et al., 2016). RE This possibly explains the sudden muscular weakness PAP Figure 2. Atypical myopathy affects the muscles of the horse. Horses and degeneration (Gonzalez-Medina, 2015). Due to this D lying down and not standing up is one of the clinical signs of atypical E myopathy. disturbance type I muscle fibres will rely on anaerobic LCY respiration which results in lactic acidosis (accumulation C Diagnosing AM based on the clinical signs is difficult ER of lactic acid) (Gonzalez-Medina, 2015). and can often lead to a wrong diagnosis as the clinical signs %00 CLINICAL SIGNS AND DIAGNOSIS 1 are very similar to those of other equine diseases (Votion, N Clinical signs often start with the sudden onset of 2012). To make sure the horse is correctly diagnosed, the O D muscle weakness and stiffness (Bochnia et al., 2015). It is environment of the horse should be checked for possible ET possible that before clinical signs appear other signs such N toxic feedstuffs that the horse could have ingested which IR as depression, oesophageal obstruction, colic and anorexia P could lead to AM. The history of the horse and laboratory appear, but this is rare (Votion & Serteyn, 2008). The disease findings should also be taken into account alongside the progresses rapidly and only a few hours after development clinical signs (Votion, 2012). A veterinarian will be able of clinical signs horses will be found lying down as they to measure the CK levels in urine and elevated CK levels are unable to stand due to the muscles being affected by will indicate muscle damage which can be related to AM the disease (Brandt et al., 1997) (Figure 2). There are a few (Karlíková et al., 2018). horses that are able to stand, or stand up after lying down, TREATMENT but these horses often stand for only a few minutes before As mentioned, currently there is no specific treatment lying down again (Votion & Serteyn, 2008). Affected for AM affected horses (Votion, 2012). Current available horses can become hypothermic (low body temperature) treatment is mainly supportive and symptomatic to but once they are stabled this is usually resolved (Votion increase survival rates (Fabius & Westermann, 2018). & Serteyn, 2008). Studies also suggest that AM is related Treatment options are resolve dehydration and electrolyte to abnormal cardiac changes in horses (Verheyen et al., imbalances, provide enough energy for affected muscles, 2012). Other possible clinical signs are dark coloured urine, eliminate toxins in the body, provide pain relief, support sweating, muscle tremors, a lowered head which can result the mitochondrial function within the muscle cells, and in oedema due to the lowered position, increased breathing, 10 11prevent further or continued intoxication and injury E, selenium, carnitine and riboflavin can support AM (Fabius & Westermann, 2018). affected horses and can increase chances of survival (Fabius & Westermann, 2018). Vitamin E is commonly One of the symptoms of AM is secreting dark urine supplemented to provide general muscle support due to its which is a sign of dehydration. Therefore, providing antioxidant properties (Fagan et al., 2017). Because of the fluids is essential for rehydration, and will enhance renal supportive function of vitamin E, it is believed that it is able clearance of excess metabolites and correction of blood to provide muscle support to horses diagnosed with AM parameters (Fabius & Westermann, 2018). A veterinarian (Finno et al., 2006). Carnitine can increase leptin levels is able to provide fluid intravenously (i.v.) until the urine which stimulates glucose uptake from the bloodstream and colour is yellow again (Fabius & Westermann, 2018). A glucose metabolism (Kranenburg et al., 2014). Riboflavin, study involving people diagnosed with rhabdomyolysis also known as vitamin B2, is one of the components of suggested to provide people approximately 6 to 12 litres FAD involved in MADD (Fabius & Westermann, 2018). in the first 24 hours after diagnosis (Zimmerman & Shen, Although, the role of riboflavin in AM is unknown, 2013). This translates to approximately 0.1 and 0.2 L/kg providing riboflavin to horses with AM has shown to be body weight of fluids (Fabius & Westermann, 2018). beneficial (van Galen et al., 2012). As previously discussed, due to AM the fatty acid PREVENTION metabolism in muscle tissue is disturbed and will shift Preventing AM is important as currently there is no from aerobic to anaerobic (Fabius & Westermann, 2018). specific treatment. Firstly, to prevent AM in grazing Anaerobic fatty acid metabolism in muscle tissue creates horses, ingestion of toxic sycamore seeds or spouts should metabolites which can disrupt homeostasis in the body be prevented by checking the environment of the horse. (Mizock & Falk, 1992). Providing enough glucose for If found, seeds and sprouts should be removed from the metabolism in the body can prevent this shift from aerobic horse’s environment (Votion et al., 2020). Providing easy to anaerobic metabolism (Fabius & Westermann, 2018). accessible feed, such as hay, in pastures with decreased Therefore, administering glucose will increase the chances grass availability, or lower quality grass, can also lower of survival, with a suggested glucose administration of 5% the risk as horses will not look for other feedstuffs in the glucose up to 20 litres per day for a 500kg horse affected pasture (Votion et al., 2009; González-Medina et al., 2017). by AM (Wüger et al., 2006; Fabius & Westermann, 2018). Grazing on fields surrounded by sycamore trees should also be avoided during autumn and spring to decrease the risk Studies suggest that the supplementation of vitamin Anouk Frieling, MSc Equine Sciences, BSc (Hons) Anouk has been involved with horses from a young age. During her time taking care of horses on yards and during the undergraduate Animal Husbandry at HAS University of Applied Sciences in the Netherlands, she developed an interest for equine nutrition. To gain more specific knowledge about equine nutrition she completed the MSc Equine Sciences at Aberystwyth University. As Senior Nutritionist at Feedmark, Anouk provides information that combines her technical knowledge and practical experience obtained from her studies and taking care of many different types of horses. 12 13stiffness but the signs of the disease are very similar to other of AM (Votion et al., 2020). Good pasture management is essential for fields close to sycamore trees. muscle diseases in horses, making it difficult to correctly diagnose a horse with AM. Currently, there is no specific SUMMARY treatment for the disease as the full pathophysiology is still Atypical myopathy is an acute seasonal disease in grazing unknown. Available treatment is mainly supportive to be horses, affecting the muscles of the horse. The onset of the able to increase the chances of survival for affected horses. disease is caused due to ingestion of sycamore seeds, sprouts Because there is no treatment available, it is important to or leaves which contain the toxic compound HGA. After implement good pasture management and prevent horses intoxication the disease progresses rapidly and is therefore from ingesting toxic composites. highly fatal. Clinical signs include muscle weakness and REFERENCES Bochnia, M., Ziegler, J., Sander, J., Uhlig, A., Schaefer, S., Vollstedt, S., Glatter, M., Abel, S., Recknagel, S., Schusser, G. F., Wensch-Dorendorf, M., & Zeyner, A. (2015). Hypoglycin a content in blood and urine discriminates horses with atypical Myopathy from clinically normal horses grazing on the same pasture. PLoS ONE, 10(9): 1-15. 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M., Linden, A., Delguste, C., Amory, H., Thiry, E., Engels, P., van Galen, G., Navet, R., Sluse, F., Serteyn, D., & Saegerman, C. (2009). Atypical myopathy in grazing horses: A first exploratory data analysis. Veterinary Journal, 180(1): 77-87. Votion, D. M., Linden, A., Saegerman, C., Engels, P., Erpicum, M., Thiry, E., Delguste, C., Rouxhet, S., Demoulin, V., Navet, R., Sluse, F., Serteyn, D., Van Galen, G., & Amory, H. (2007). History and clinical features of atypical myopathy in horses in Belgium (2000-2005). Journal of Veterinary Internal Medicine, 21(6): 1380-1391. Votion, D. M., & Serteyn, D. (2008). Equine atypical myopathy: A review. Veterinary Journal, 178(2): 185–190. Votion, D. M. (2012). The Story of Equine Atypical Myopathy: A Review from the Beginning to a Possible End. ISRN Veterinary Science, 2012: 1–14 Westermann, C. M., Dorland, L., Votion, D. M., de Sain-van der Velden, M. G. M., Wijnberg, I. D., Wanders, R. J. A., Spliet, W. G. M., Testerink, N., Berger, R., Ruiter, J. P. N., & van der Kolk, J. H. (2008). Acquired multiple Acyl-CoA dehydrogenase deficiency in 10 horses with atypical myopathy. Neuromuscular Disorders, 18(5): 355-364. Westermann, C. M., van Leeuwen, R., van Raamsdonk, L. W. D., & Mol, H. G. J. (2016). Hypoglycin A Concentrations in Maple Tree Species in the Netherlands and the Occurrence of Atypical Myopathy in Horses. Journal of Veterinary Internal Medicine, 30(3): 880-884. Wüger, C., Straub, R., & Gerber, V. (2006). Intravenöse flüssigkeitstherapie beim pferd. Pferdeheilkunde, 22(3): 327-336. Zimmerman, J. L., & Shen, M. C. (2013). Rhabdomyolysis. Chest, 144(3): 1058- 1065. Żuraw, A., Dietert, K., Kühnel, S., Sander, J., & Klopfleisch, R. (2016). Equine atypical myopathy caused by hypoglycin A intoxication associated with ingestion of sycamore maple tree seeds. Equine Veterinary Journal, 48(4): 418-421. 12 13Nutritional support for pituitary pars intermedia dysfunction Dr. Stephanie Wood, PhD Equine Nutrition, PgDip, BSc (Hons), RNutr (Animal), R.Anim.Tech Pituitary pars intermedia dysfunction (PPID) is a neurosecretory cells acting on the posterior lobe release common disease predominantly diagnosed in horses and their hormones directly into the posterior lobe (Frandson ponies, although it can also affect donkeys. It is a condition & Spurgeon, 1992; Dyce et al., 1996). Research has also associated with ageing, with 15%-30% of horses and shown that neurons secreting dopamine (dopaminergic ponies over the age of 15 affected (Ireland & McGowan, neurons) originating from the periventricular nucleus of the 2018, EEG, 2021), although it has been diagnosed in hypothalamus, terminate in the pars intermedia (McFarlane equids as young as seven (Heinrichs et al., 1990). It is et al., 2005). This difference is important to understand the termed an endocrine disease, meaning that the organs pathophysiology of PPID. producing hormones within the horse’s body are not Both lobes of the pituitary gland secrete hormones that functioning correctly. Specifically, the pars intermedia of are vital for maintenance of body systems and health. the pituitary gland is affected, leading to the name pituitary When hormone secretion is below or above requirements pars intermedia dysfunction. imbalances develop, which over time lead to illness. In Tail PATHOPHYSIOLOGY OF PPID equids with PPID this imbalance relates to hormones produced by the pars intermedia of the anterior lobe of the The pituitary gland sits at the base of the brain, suspended pituitary gland. The change in hormone secretion is due to below the hypothalamus by the pituitary stalk (Figure degeneration of the dopaminergic neurons (EEG, 2021), 1). The pituitary gland comprises two distinct parts, the which occurs as part of the normal ageing process but may anterior lobe (also known as the adenohypophysis) located also be due to oxidative stress (Reed et al., 2018), with towards the front of the gland, and the posterior lobe (also known as the neurohypophysis) positioned towards the rear of the gland. Each lobe comprises of specific parts; the pars tuberalis, pars intermedia and pars distalis comprise the anterior lobe, and the pars nervosa and infundibular stalk comprise the posterior lobe (Dyce et al., 1996). The pituitary gland is known as a major endocrine gland as it produces hormones that directly influence other endocrine glands, and therefore the production of other hormones (Dyce et al., 1996). The production and secretion of hormones from the pituitary is regulated by the hypothalamus, or more accurately, by hormones secreted by neurosecretory cells of certain parts of the hypothalamus. Neurosecretory Figure 1. Location of the pituitary gland and hypothalamus in humans. cells acting on the anterior lobe discharge their hormones Locations are similar in equids. A – Anterior lobe of pituitary gland, P – into a capillary system serving the anterior lobe, whereas Posterior lobe of pituitary gland, H – Hypothalamus. 14 15this degenerative loss being accelerated in some horses 2016; Schemthaner-Reiter et al., 2021). In healthy equids (Frank, 2015). This leads to PPID also being thought of as cortisol levels are maintained within a normal range by a a neurodegenerative disease. feedback system that in response to raised plasma cortisol levels, reduces CRH secretion from the hypothalamus In non-PPID equids, dopaminergic neurons release leading to a consequential reduction in ACTH secretion. dopamine that interacts with receptors on melanotrope cells If ACTH levels are persistently raised the adrenal cortex which comprise the pars intermedia. Melanotrophs produce becomes hyperplasic and circulating cortisol levels remain pro-opiomelanocortin (POMC) which is a prohormone high. Increased cortisol levels have negative effects on the that is enzymatically converted to the hormones alpha- Pituitary pars intermedia dysfunction (PPID) is a body, causing persistent high blood glucose, decreased melanocyte-stimulating hormone (α-MSH), corticotropin- common disease predominantly diagnosed in horses and insulin sensitivity and a reduced immune response that like intermediate peptide (CLIP) and β-endorphin (Frank, ponies, although it can also affect donkeys. It is a condition delays healing (Fortin et al., 2021). Such physiology 2015; Reed et al., 2018). Only a very small amount of associated with ageing, with 15%-30% of horses and explains many of the symptoms displayed by PPID affected adrenocorticotropic hormone (ACTH) is produced by the ponies over the age of 15 affected (Ireland & McGowan, equids, however recent research shows that only about normally functioning pars intermedia. The production of 2018, EEG, 2021), although it has been diagnosed in 20% of PPID cases will present with enlarged adrenal POMC and its associated hormones is under the control of equids as young as seven (Heinrichs et al., 1990). It is cortex and increased circulating cortisol despite having dopamine, with dopamine secretion inhibiting melanotrope termed an endocrine disease, meaning that the organs R increased ACTH levels (Reed et al., 2018). This suggests E POMC production in normal conditions, however in PPID producing hormones within the horse’s body are not P that other factors are important for the development of A affected equids, the degeneration of dopaminergic neurons P functioning correctly. Specifically, the pars intermedia of D PPID symptoms. E reduces this inhibitory control. As such, melanotrophs the pituitary gland is affected, leading to the name pituitary LC become more active leading to an increase in the number SYMPTOMS OF PPID Y pars intermedia dysfunction. CE Tail of melanotrope cells (hyperplasia), enlargement of the pars The symptoms commonly exhibited by equids with PPID R PATHOPHYSIOLOGY OF PPID % intermedia and development of adenoma (non-cancerous include being prone to laminitis, insulin dysregulation (ID), 00 The pituitary gland sits at the base of the brain, suspended 1 tumour) within the pars intermedia (Frank, 2015; EEG, excessive hair growth, poor coat quality, failure to shed a N below the hypothalamus by the pituitary stalk (Figure O 2021). The overactive melanotrophs produce more POMC thick winter coat, excessive sweating (hyperhidrosis), D 1). The pituitary gland comprises two distinct parts, the E leading initially to increased α-MSH and CLIP secretion, weight loss, muscle wastage, development of regional fat TN anterior lobe (also known as the adenohypophysis) located I followed by increased ACTH production as the disease pads, excessive urine production and urination (polyuria), RP towards the front of the gland, and the posterior lobe (also progresses (Frank, 2015). It is the excessive secretion of excessive thirst (polydipsia), recurrent infections, increased known as the neurohypophysis) positioned towards the rear these hormones, particularly ACTH, that is thought to lead susceptibility to parasite infections, reduced response to of the gland. Each lobe comprises of specific parts; the pars to the clinical signs of PPID, although the exact processes pain, lethargy, change in appetite and even blindness (Reed tuberalis, pars intermedia and pars distalis comprise the involved are not fully understood. et al., 2018; EEG, 2021). Of these symptoms, excessive hair anterior lobe, and the pars nervosa and infundibular stalk growth is the most common (55%-80% of cases) and the In non-PPID animals ACTH is primarily secreted from increased risk of laminitis potentially the most debilitating. comprise the posterior lobe (Dyce et al., 1996). The pituitary the pars distalis of the anterior lobe in response to stimuli gland is known as a major endocrine gland as it produces by corticotropin-releasing hormone (CRH) from the INCREASED RISK OF LAMINITIS hormones that directly influence other endocrine glands, hypothalamus. Once secreted, ACTH acts on the adrenal Why equids with PPID often suffer from chronic laminitis and therefore the production of other hormones (Dyce cortex of the adrenal glands, stimulating the secretion of has been a key research focus over recent years. We know et al., 1996). The production and secretion of hormones glucocorticoids (cortisol, corticosterone and cortisone) that ID is a key component of endocrinopathic laminitis from the pituitary is regulated by the hypothalamus, or (Gallo-Payet et al., 2017). Cortisol has many functions (see Equine metabolic syndrome and Update on laminitis) more accurately, by hormones secreted by neurosecretory although its main functions relate to the body’s response and that ID occurs in 30%-60% of PPID cases, although to physical and emotional stress, during which it stimulates prevalence could be as high as 77% (Horn et al., 2019; cells of certain parts of the hypothalamus. Neurosecretory an increase in available energy causing hyperglycaemia Tadros et al., 2019). Karikoski et al. (2016) confirmed the cells acting on the anterior lobe discharge their hormones (raised blood glucose) and decreases sensitivity (Hart et al., role of hyperinsulinemia in laminitis in a study comparing into a capillary system serving the anterior lobe, whereas 14 15circulating insulin levels in a group of PPID horses. should follow recommendations by your vet, aligning to Hyperinsulinemia was present in all horses with laminitis those by Professor Menzies-Gow in Update on laminitis, and absent in those without laminitis. Such results indicate and should include providing appropriate pain relief and that laminitis may be a result of ID rather than PPID, whilst foot support alongside feeding an appropriate diet. also explaining why PPID horses with hyperinsulinemia FEEDING RECOMMENDATIONS appear to be at the highest risk of developing laminitis. Feeding recommendations for equids with PPID are Research by Tadros et al. (2019) further supports the role influenced by the presence or absence of hyperinsulinemia of high circulating insulin in laminitis, finding that plasma and other associated health problems, and align to those for insulin concentrations increased with laminitis severity. equids with EMS and ID. Like all equids, fibre should be How PPID and hyperinsulinemia are linked however is less the main constituent of the diet for equids with PPID, with clear. The role of cortisol continues to be considered, and quality protein, vitamins and minerals provided to balance recent research showing that equids with PPID and ID have the diet. If additional energy is needed to maintain body higher circulating unbound cortisol (free cortisol fraction, weight options include higher energy fibre feeds such as FCF) compared to healthy equids whilst having similar alfalfa and oil-coated forages, high fat feeds such as linseed total cortisol concentrations may explain this link (Hart et al., 2016; Vaughn et al., 2022). Free cortisol is biologically active and therefore promotes raised blood glucose and antagonises (inhibits) the effects of insulin, leading to the hyperinsulinemia often seen in equids with PPID. Research continues to investigate this link and determine other contributing factors to the high risk of laminitis that PPID equids demonstrate. Figure 2. Composition of water-soluble carbohydrates (WSC) and non-structural carbohydrates (NSC) used to describe the nutritional MANAGEMENT AND FEEDING OF PPID properties of plants. Equids displaying clinical symptoms of PPID, or older or oils, or appropriate concentrate feeds. For PPID equids than 10 years of age with chronic laminitis issues, should be all feeds should be low in starch and sugars to help maintain assessed by a vet for the development of PPID, whilst testing low blood glucose and insulin levels. Ideally feedstuffs for ID is recommended in all PPID cases (Durham et al., should have a non-structural carbohydrate (NSC) level less 2014; EEG, 2021). Upon PPID diagnosis the vet will lead than 10% of dry matter (DM) (Borgia et al., 2011; Harris the treatment and management plan that will incorporate et al., 2017; EEG, 2020) (Figure 2), which can preclude drug therapy and husbandry recommendations. Pergolide concentrate feeds, however there are now feeds and remains the medication of choice, with regular blood tests supplements on the market specifically designed to provide used to monitor ACTH levels and response to treatment energy whilst having a low NSC content. (EEG, 2021). Husbandry requirements will be dictated by issues associated with PPID. Correct hoof care to maintain Forage should ideally be tested for its NSC content as hoof balance and increased monitoring of parasite burdens there is no way of knowing the nutritional content without are some examples of the additional needs that PPID equids testing. Assumptions that meadow hays are lower in NSC may have. Other considerations include regular dental care, are misplaced as the level of NSC accumulation in the monitoring of skin health due to increased susceptibility growing plant, and therefore the preserved forage, varies to skin infections and ensuring access to clean water is with climate, stage of growth, health of the plant when available at all times. Management of laminitis episodes harvested and geographical area (Richards et al., 2021). Hay 16 17The amount to feed will depend on the animal’s body is recommended over haylage for equids with metabolic condition. Those of lean condition should be fed 2%- issues due to its lower digestible energy (DE) content, 2.5% of their body weight as suitable forages and high which is an important consideration for overweight equids, fat/oil feedstuffs. Animals that are overweight should be although DE levels would also need confirming through fed a diet and ration that promotes weight loss. For some laboratory analysis. Haylage preserved anaerobically animals replacing a portion of the hay ration with hygienic and with a DM content of 50%-70% should have lower straw maybe enough to induce weight loss whilst allowing sugar levels than hay due to fermentation processes (see them to eat for extended periods of time and perform Forage options for horses) however many haylages have a higher DM content, limiting the degree of fermentation and leading to the production of wrapped hay rather than haylage. In these instances, the sugar levels may be higher than hay, particularly if the plant was cut at an earlier stage of growth. Soaking continues to be used as a method to reduce sugar levels in hays, and current recommendations for PPID, RE ID and EMS equids are to soak hay for a minimum of 60 PA minutes (EEG, 2020) although longer times may be needed P DE (Figure 3). The efficacy of soaking hay to achieve a NSC LC level below 10% will depend on the level of NSC prior to YCE soaking and on the soaking conditions. Argo et al. (2015) R % report water-soluble carbohydrate (WSC – sugars and 00 Figure 3. Soaking can be a useful way of reducing water-soluble 1 fructan) losses from grass hay with a starting WSC level carbohydrate (WSC) levels in hay although efficacy will be influenced by N water temperature and soaking time. O of 18% DM. After 7 hours soaking at ambient temperature DE WSC levels decreased by 24% to 14% DM, whilst after T normal feeding behaviours. If straw is added to the diet it NI 16 hours soaking (overnight) in the same conditions levels RP should be gradual to allow adaptation to the higher intake decreased by 41% to 10.5% DM. In warmer conditions of indigestible fibre. Daily food intake may need to be the time to achieve WSC losses is reduced and therefore limited to 1.5% body weight as DM per day (e.g. 6.75kg soaking time can be shortened (Longland et al., 2014) as per day for a 450kg horse) to induce weight loss, although demonstrated by Bochnia et al. (2021) who found that this should be guided by your vet or a qualified nutritionist oC can reduce WSC soaking for just 15 and 30 minutes at 22 (Shepherd et al., 2021). Feeding less than this amount may content by 13%-24% and 23%-34%, respectively. In the be required for equids resistant to weight loss however this same study it was also found that soaking hays of low WSC is not recommended unless advised by your vet who should content (2.5%-6.6% WSC) had little effect on post-soaking regularly monitor the animal’s response to such restricted WSC levels. Due to concerns about hygienic quality of food intake. When on restricted intake the use of slow long soaking times (Moore-Colyer et al., 2014), soaking feeders should also be considered as a way of prolonging duration should be shortened to 1-2 hours in warm weather eating time and supporting digestive health and allowing (Durham et al., 2019). It is also highlighted that soaking natural feeding behaviour. causes loss of minerals and trace elements therefore a PASTURE ACCESS AND INTAKE balancer or mineral supplement will be required to meet Similar to management and feeding recommendations, nutrient requirements. 16 17access to pasture will be guided by the presence of pasture intake see Managing our horse’s grass intake. hyperinsulinemia and episodes or risk of laminitis, rather During laminitic episodes animals should be removed from than a diagnosis of PPID per se. Non-structural carbohydrate the pasture completely until the condition is under control levels of pasture vary considerably therefore management and hoof structures are stable. Controlled pasture access of intake is usually required for equids with PPID and may then be possible although some equids with ID are ID who can consume large amounts if given free access. very sensitive to pasture and are more stable on dry-lot Methods of pasture restriction include limiting grazing area, turnout areas and controlled feeding of forages. limiting grazing time and use of a grazing muzzle. Limiting Monitoring the amount of pasture available in a field grazing area can be achieved using electric fencing and can be challenging as fresh grass is often grazed as soon as works well combined with strip grazing. Limiting grazing it grows. As such, visual assessment of how much pasture time is only effective if the amount of pasture available per there is available to eat is difficult. Sectioning off a small animal is also limited, as equids are able to increase their 2) with electric fencing prevents new area of the field (1-2m intake rate to compensate for the shorter grazing period growth being consumed and allows pasture growth and (Ince et al., 2011; Wood et al., 2012; Glunk et al., 2013). availability to be monitored. The fenced area should be in Limiting grazing time is most effective when the available parts of the field which are actively grazed and it should be pasture is sparse, preventing this compensatory behaviour. moved every 1-2 weeks to ensure an accurate representation Use of grazing muzzles can considerably reduce pasture of the pasture being consumed. intake whilst allowing animals to move freely, exercise and SUMMARY socialise, however they should be introduced gradually to Pituitary pars intermedia dysfunction is a disease give time to become accustomed to wearing the muzzle and affecting primarily older equids but which should be learning how to drink. If muzzles are worn for part of the considered in equids over the age of 10 with recurrent day, once the muzzle is removed the same compensatory laminitis. Abnormal hair growth and shedding, changes intake of pasture may be seen (Longland et al., 2016; Davis et al., 2020). For more in-depth information on restricting in body condition and composition, polyuria, polydipsia, Dr Stephanie Wood, PhD, PgDip, BSc (Hons), RNutr (Animal), R.Anim.Tech Stephanie has many years’ experience managing horses in both a private and professional capacity. During her time caring for different horses she developed a keen interest in nutrition which lead her to gain her undergraduate degree in Equine Science from Aberystwyth University, followed by a PhD in Equine Nutrition from the Royal (Dick) School of Veterinary Studies at the University of Edinburgh. These academic achievements are recognised in her certifications as a Registered Animal Nutritionist and Registered Animal Technologist. Stephanie has a passion for helping others to learn and understand which was utilised in her positions as Senior Equine Technologist where she developed training and educational material for the equine industry, and as Senior Lecturer where she tutored the next generation of equine professionals. Stephanie’s passion for helping others combined with her hands-on industry experience and technical knowledge enable her to support owners with practical advice and guidance in her role as Director of Science and Nutrition at Feedmark. 18 19fibre and balanced for protein, vitamins and minerals is and reduced immunity are the most common symptoms. advocated alongside controlled pasture intake. Quality Insulin dysregulation is present in some but not all PPID of life for equids with PPID is increased where feeding cases, but for those with hyperinsulinemia management and management recommendations are combined with and feeding should align to recommendations for ID appropriate veterinary treatment. and EMS equids. A diet low in starch and sugar, high in REFERENCES Argo, C.McG, Dugdale, A.H.A., & McGowan, C.M. (2015). Considerations for the use of restricted, soaked grass hay diets to promote weight loss in the management of equine metabolic syndrome and obesity. The Veterinary Journal, 206: 170-177. Bochnia, M., Pietsch, C., Wensch-Dorendorf, M., Greef, M., & Zeyner, A. (2021). Effect of Hay Soaking Duration on Metabolizable Energy, Total and Prececal Digestible Crude Protein and Amino Acids, Non-Starch Carbohydrates, Macronutrients and Trace Elements. Journal of Equine Veterinary Science, 101: 103452. Borgia, L., Valberg, S., McCue, M., Watts, K., & Pagan, J. (2011). Glycaemic and insulinaemic responses to feeding hay with different non-structural carbohydrate content in control and polysaccharide storage myopathy-affected horses. Journal of Animal Physiology and Animal Nutrition, 95(6): 798-807. Davis, K.M., Iwaniuk, M.E., Dennis, R.L., Harris, P.A., & Burk, A.O. (2020). Effects of grazing muzzles on behavior and physiological stress of individually housed grazing miniature horses. Applied Animal Behaviour Science, 231: 105067. Durham, A,E., Frank, N., McGowan, C.M., Menzies-Gow, N.J., Roelfsema, E., Vervuert, I., Feige, K. & Fey, K. (2019) ECEIM Consensus Statement on Equine Metabolic Syndrome. Journal of Veterinary Internal Medicine, 33: 335-349 Durham, A.E., McGowan, C.M., Fey, K., Tamzali, Y., & van der Kolk, J.H. (2014). Pituitary pars intermedia dysfunction: diagnosis and treatment. Equine Veterinary Education, 26(4): 216-223. Dyce, K.M., Sack, W.O., & Wensing, C.J.G. (1996). Textbook of Veterinary Anatomy, 2nd edn. New York, USA: W.B. 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Robinson's Current Therapy in Equine DE Medicine (7th edn) (pp 574-577). Missouri, USA: Saunders. L Gallo-Payet, N., Martinez, A., & Lacroix, A. (2017). Editorial: ACTH Action in the Adrenal Cortex: From Molecular Biology to Pathophysiology. Frontiers in CY Endocrinology, 8: 101. C Glunk, E.C., Pratt-Phillips, S.E., & Siciliano, P.D. (2013). Effect of Restricted Pasture Access on Pasture Dry Matter Intake Rate, Dietary Energy Intake, and ER Fecal pH in Horses. Journal of Equine Veterinary Science, 39: 421-426. Harris, P.A., Ellis, A.D., Fradinho, M.J., Jansson, A., Julliand, V., Luthersson, N., Santos, A.S., & Vervuert, I. (2017). Review: Feeding conserved forage to %0 horses: Recent advances and recommendations. Animal, 11(6): 958-967. 01 Hart, K.A., Wochele, D.M., Norton, N.A., McFarlane, D., Woolridge, A.A., & Frank, N. (2016). Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses. 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Epidemiology of pituitary pars intermedia dysfunction: A systematic literature review of clinical presentation, disease prevalence and risk factors. The Veterinary Journal, 235: 22-33. Karikoski, N.P., Patterson-Kane, J.C., Singer, E.R., McFarlane, D., & McGowan, C.M. (2016). Lamellar pathology in horses with pituitary pars intermedia dysfunction. Equine Veterinary Journal, 48: 472-478. Longland, A., Barfoot, C., & Harris, P. (2014). Effect of water temperature and agitation on loss of water-soluble carbohydrates and protein from grass hay: implications for equine feeding management. Vet Record, 174: 68 Longland, A.C., Barfoot, C., & Harris, P.A. (2016). Efficacy of Wearing Grazing Muzzles for 10 Hours per Day on Controlling Bodyweight in Pastured Ponies. Journal of Equine Veterinary Science, 45: 22-27. McFarlane, D., Dybdal, N., Donaldson, M.Y., Millert, L., & Cribb, A.E. (2005). Nitration and Increased α-Synuclein Expression Associated with Dopaminergic Neurodegenration In Equine Pituitary Pars Intermedia Dysfunction. Journal of Neuroendocrinology, 17: 73-80. Moore-Colyer, M.J., Lumbis, K., Longland, A., & Harris, P. (2014). The effect of five different wetting treatments on the nutrient content and microbial concentration in hay for horses. PLoS One, 9(11): e114079. Reed, S.M., Bayly, W.M., & Sellon, D.C. (2018). Chapter 16 Disorders of the Endocrine System. In: Reed, S.M., Bayly, W.M., & Sellon, D.C (eds). Equine Internal Medicine (4th edn) (pp1029-1138). Missouri, USA: Saunders. Richards, N., Nielsen, B., & Finno, C.J. (2021). Nutritional and Non-nutritional Aspects of Forage. Veterinary Clinics of North America: Equine Practice, 37(1): 43-61. Schemthaner-reiter, M., Wolf, P., Vila, G., Luger, A. (2021). The Interaction of Insulin and Pituitary Hormone Syndromes. Frontiers in Endocrinology, 12: 626427. Shepherd, M., Harris, P., & Martinson, K.L. (2021). Nutritional Considerations When Dealing with an Obese Adult Equine. Veterinary Clinics of North America: Equine Practice, 37(1): 111-137. Tadros, E.M., Fowlie, J.G., Refsal, K.R., Marteniuk, J., & Schott II, H.C. (2019). Association between hyperinsulinaemia and laminitis severity at the time of pituitary pars intermedia dysfunction diagnosis. Equine Veterinary Journal, 51: 52-56. Vaughn, S.A., Norton, N.A., & Hart, K.A. (2022). Circulating Hypothalamic-Pituitary-Adrenal Axis Hormones and Insulin Concentrations in Horses and Ponies. Journal of Equine Veterinary Science, 111: 103810. Wood, S.J., Smith, D.G., Morris, C.J., & Cuddeford, D. (2012). The effect of pasture restriction on dry matter intake of foraging donkeys in the United Kingdom. In: Saastamoinen M., Fradinho M.J., Santos A.S., Miraglia N. (eds) Forages and grazing in horse nutrition. Forages and grazing in horse nutrition, vol 132. Wageningen Academic Publishers, Wageningen. 18 19The importance of respiratory health Anouk Frieling, MSc Equine Sciences, BSc (Hons) Horses are hindgut fermenters, therefore high-fibre is required for energy production within the body, which is forage forms the basis of their diet. The most common an essential component for exercising muscles (Franklin et forage fed to horses is field dried hay (Moore-Colyer et al., al., 2012). Exercise increases the energy requirement of the 2016). High quality and fibrous hay provides a large portion muscles, therefore during exercise ventilation of the lungs of the daily energy requirements of the horse (Fernandes et increases to accommodate this increasing energy demand al., 2014), with the nutrient quality of hay depending on (Franklin et al., 2012). Healthy adult horses consume the stage of growth during harvest and the grass mixture approximately 80 litres of air per minute whilst at rest (Earing et al., 2013). Horse owners often assess the quality (Mazan, 2022). When horses exercise this can increase of hay through a visual assessment and by smelling the hay up to 180 litres per minute to deliver enough oxygen to (Moore-Colyer et al., 2016). Even when hay appears to be provide energy to the exercising muscles (Mazan, 2022). of a high quality after such an assessment, it can contain Walk and trot seem to have little effect on the breathing high levels of respirable dust (Intemann et al., 2022). pattern of the horse, however canter significantly increases Unhygienic forage can have an effect on the respiratory the requirement for oxygen in horses (Robinson, 1985). system and horses can develop chronic respiratory diseases Besides providing oxygen and removing carbon dioxide which influence overall health and performance (Pirie, from the blood stream, the respiratory system also has an 2014). This article will review the importance of a healthy important role in immune responses in the body (Grzela respiratory system, the effect of forage on respiratory et al., 2012). The respiratory tract is often exposed to health, forage that supports a healthy respiratory tract and environmental factors, such as bacteria and viruses, that management options that can improve respiratory health could potentially cause infection or disease (Whitsett & and prevent respiratory diseases. Alenghat, 2015). The respiratory system, specifically the IMPORTANCE OF THE RESPIRATORY SYSTEM airway epithelium (Parker & Prince, 2011), are the first line of defence against these pathogens and are therefore The respiratory system of the horse consists of the nose, mouth, pharynx (throat), larynx, trachea (windpipe), bronchi, bronchioles, alveoli and the lungs (Lekeux et al., 2014). Respiratory muscles, such as the diaphragm, expand and compress the chest wall therefore stimulating breathing motions resulting in inhalation and exhalation of gas (Robinson, 2007). The function of the respiratory system is to remove carbon dioxide from the circulatory system and deliver oxygen to the body (Mazan, 2022). Exchange of gasses occurs in the alveoli which are lined with a pulmonary capillary network (McGorum et al., 2007) (Figure 1). During each breath, the horse inhales Figure 1. The respiratory system of the horse has an important function in exchange of gasses and is part of the innate immune system. In approximately 4-5 litres of air, although the total capacity the alveoli the exchange of gasses takes place, delivering oxygen and of the lungs is roughly 42 litres (Robinson, 2007). Oxygen removing carbon dioxide from the blood. 20 21part of the innate immune system (Martin & Frevert, 2005). The epithelial cells serve as a protective barrier and prevent the entry of pathogens into the alveoli where gas exchange takes place (McGorum et al., 1998; Johnston et al., 2021). When the epithelial cells come in contact with harmful pathogens, it triggers an immune response in the body to inactivate the pathogens before causing an Figure 2. Dust can irritate the respiratory tract causing the horse to infection (Gilkerson et al., 2015). A healthy, functioning, sneeze or cough occasionally. Once the horse is exposed to dust for a prolonged period the horse can develop a chronic respiratory disease. respiratory tract is important for the delivery of oxygen, therefore, if respiratory health decreases due to foreign (Figure 2). Clinical signs of chronic respiratory diseases particles that irritate the respiratory system, it can have are increased mucous production, a recurrent cough, an effect on overall health and performance of the horse, increased respiratory effort and poor performance (Ivester making it important to maintain respiratory health through et al., 2014). optimal management. Inflammatory airway disease is one of the most common THE EFFECT OF FORAGE ON RESPIRATORY respiratory diseases in athletic horses caused by respirable HEALTH RE dust (Ivester et al., 2014). Often, IAD is characterised by P When respirable dust or mycotoxins enter the respiratory AP mild inflammation of the respiratory tract, but even mild tract, most particles deposit on the epithelium, from which DE inflammation has a negative effect on respiratory health and L they are cleared meaning they are unable to cause harm CY equine performance (Sánchez et al., 2005). Sánchez et al. C (Ganesan et al., 2013). However, respirable dust smaller E (2005) analysed the effect of IAD on the gas exchange in the R than 5 microns (μm) is able to travel down the alveoli % respiratory tract during high-speed exercise in racehorses. 00 and trigger an immune response (Auger & Moore-Colyer, 1 The study suggested that due to the respiratory disease, N 2017). If small dust particles enter the respiratory tract O horses experienced impaired pulmonary gas exchange D they irritate the airway mucosa receptors which trigger a E which is likely to negatively affect the performance of the T response from the horse causing them to cough or sneeze NI horses (Sánchez et al., 2005). RP as a way of clearing unwanted particles from the airway Recurrent airway obstruction, previously known (McGorum, 2002; Robinson et al., 2003). When horses as chronic obstructive pulmonary disease (COPD), is are exposed to an environment containing a high amount a respiratory disease caused by respirable dust in the of foreign particles, it takes between 3 and 5 hours before environment of the horse, but due to management changes, neutrophils are present in the respiratory tract. Neutrophils such as providing a dust free environment, the disease can are a key component of the immune response of the body be managed (Pirie, 2014). Symptoms following prolonged triggered by dust particles (Brazil et al., 2005; Leclere et dust exposure that leads to RAO, often get worse after al., 2011). If horses are exposed to dust for a short period, exercise (Léguillette, 2003; Niedzwiedz et al., 2014). between 5 and 7 hours, the effect of the inflammation Clinical signs of RAO can also disappear when horses are can be reversed within four days if the dust is removed out on pasture but will reoccur as soon as the horse enters from the environment (Brazil et al., 2005; Leclere et al., the dusty environment due to irritation of the respiratory 2011). However if dust irritates the respiratory tract for a tract (Williamson & Davis, 2007; Niedzwiedz et al., 2014). prolonged period horses can develop chronic respiratory Neutrophilic inflammation in the respiratory tract, due to diseases such as inflammatory airway disease (IAD) also known as equine asthma and recurrent airway obstruction RAO, can cause bronchospasms and over production of (RAO) (Vandenput et al., 1998; Séguin et al., 2010) mucous (Davis & Rush, 2002; Gehlen et al., 2008). The 20 21is silage (Müller, 2018). Silage is also a forage which is severity of the obstruction in the respiratory tract depends harvested earlier than hay and contains a higher moisture on the stage of the disease which is connected to the content, therefore decreasing the respirable dust in the amount of time spend in a dusty environment (Niedzwiedz forage and the environment of the horse (Olave et al., et al., 2014). These changes in the respiratory tract can 2021). The median dry matter percentage of high-quality be managed by administering medication or removing silage measured in a study on horse farms in Switzerland, the horse from the dusty environment (Niedzwiedz was 65.8% (Wichert et al., 2008). Therefore suggesting et al., 2014). that high-quality silage can be used as a suitable hay FORAGE FOR RESPIRATORY HEALTH replacement. Results from a study carried out by Vandenput The digestive tract of the horse is adapted to ferment et al. (1998) suggested that silage aids the maintenance of a high-fibre feedstuff into volatile fatty acids (VFA), which stable respiratory system in horses diagnosed with COPD, are used as an energy source for various processes in the also known as equine asthma. Thus indicating that silage is body (Intemann et al., 2022). Grass hay is a high-fibre a suitable forage to feed to support respiratory health. forage which is commonly fed to horses, but in countries such as Sweden and Finland hay is often replaced with Even though silage is a suitable forage to increase and haylage (Besier et al., 2013). Reasons given for this switch maintain respiratory health there are a few considerations were difficulties with storing hay in a dry place to prevent that should be taken into account before switching to moulding, and horses displaying symptoms of respiratory silage. Silage is higher in energy therefore feeding a diseases after feeding hay (Müller, 2018) (Figure 3). smaller portion, compared to hay, will meet the energy Feeding hay to stabled horses has been associated with a requirements of the horse (Müller et al., 2007). Although tenfold increase of respirable dust in the environment of the the energy content is higher, the amount of fibre is lower horse (McGorum et al., 1998). (Müller et al., 2007). This type of forage is wrapped and stored, but once the seal breaks and air is able to enter the Haylage is made from grass that is cut earlier than grass bale, the amount of toxins increases and it moulds, making used for hay production (Müller, 2018). After cutting and it unsuitable to feed to horses (McNamara et al., 2002; drying the grass until it reaches the correct dry matter Müller et al., 2007). percentage, haylage is wrapped in plastic (Clements & Pirie, 2007). Due to the plastic wrapping, a fermentation process occurs, preserving nutrients of the forage and resulting in lower dust content in the forage (Clements & Pirie, 2007). Replacing hay with haylage can result in a reduction of 60 to 70% of the respirable dust in the environment of the horse (Clements & Pirie, 2007). Olave et al. (2021) studied the effect of feeding haylage instead Figure 3. There are other forage options instead of hay which have a of hay on pro-inflammatory markers in racehorses. Results lower dust content. Horses are often fed haylage or silage. concluded that haylage reduces exposure to respirable MANAGEMENT OF RESPIRATORY HEALTH AND dust and therefore irritation of the respiratory tract, and PREVENTION resulted in the suppression of airway neutrophilia, which Horses with severe respiratory diseases require long- indicates a decreased inflammatory response in the body term management (van Erck-Westergren et al., 2013). (Olave et al., 2021). Respiratory diseases can mainly be managed by providing Another forage option, which is being fed more often an environment that is as dust free as possible (see nowadays to reduce exposure to environmental irritants, Industry update: Biosecurity in equine premises) or by 22 23providing medication prescribed by veterinarians suitable period, steaming hay for 50 minutes at 100 degrees Celsius for management of respiratory diseases. To support the reduces dust content but does not have a negative effect on respiratory tract horses can also undergo steam inhalation water-soluble carbohydrates or minerals such as calcium, therapy as an alternative treatment (Cha & Costa, 2017). sodium, magnesium, zinc and copper. Humer et al. (2019) did suggest that steaming hay at 100 degrees Celsius Respiratory diseases can be avoided by ensuring the decreases the dry matter content of hay and therefore adds environment contains a low dust percentage. This can more moisture, making the hay more susceptible to moulds be achieved by ensuring that forage that is fed contains and yeast when stored. But after storing steamed hay for a low dust content, by using low-dust bedding materials 24 hours the quality of the hay was not negatively affected and providing ventilation in the stables, and by allowing (Humer et al., 2019). In conclusion, hay-steaming provides as much time out of the stables as possible. As mentioned a long-term solution to increase hygienic quality of hay and earlier, there are also other forage options which prevent or manage respiratory diseases in horses. contain less dust and will therefore support a healthy respiratory system. SUMMARY The respiratory system of the horse has an important Soaking hay is a commonly used method to lower the R function in gas exchanges and overall health and E dust content in hay. It is suggested that soaking hay for 5 to PA performance. Therefore, if the respiratory tract is P 10 minutes decreases respirable dust in hay but maintains DE irritated or compromised this influences the health of L hay quality (Clarke & Madelin, 1987). Even though this CY the horse and the performance. Respirable dust in the C method has been shown to reduce content, it also decreases ER horse’s environment originating from forage can cause the amount of valuable minerals and increases the bacterial %0 an inflammatory response in the respiratory tract. If the 0 concentration (Moore-Colyer, 1996). Warr & Petch (1993) 1 respiratory system is irritated for a prolonged period, N stated that soaking hay for a 12-hour period significantly O horses can develop a chronic respiratory disease such D decreases the water-soluble carbohydrate content in hay. ET as equine asthma, also known as inflammatory airway N The dry matter content decreased by 2-4% whilst crude IRP disease, or recurrent airway obstruction. Clinical signs of protein decreased approximately 1.5-2%. Therefore, respiratory diseases are increased production of mucous, soaking hay for a longer period degrades the quality of the developing a recurrent cough and poor performance. As hay (Moore-Colyer et al., 2016). respirable dust often originates from hay, it is an option Another more recently developed method is steaming to provide different types of forages such as haylage and hay to lower the dust content using a commercial steamer. silage which usually contain a lower dust content but still Steaming hay is a method which results in decreased provide the required nutrients. Horses that develop airway airborne respirable particles whilst maintaining mineral disease require suitable long-term management through and protein content and therefore not decreasing forage for example, medication and removing the horse from the quality (Moore-Colyer et al., 2016). Humer et al. (2019) dusty environment. Over recent years, steaming has been concluded that hay steaming decreases yeast and mould adopted as a suitable method to reduce the dust content in especially in hay that has been hygienically compromised, hay whilst maintaining nutrient quality. In contrast, soaking therefore improving the quality. Moore-Colyer et al. (2016) hay has been shown to reduce nutrient content and hygienic showed that, in comparison to soaking hay for a long quality of the forage. 22 23REFERENCES Auger, E. J., & Moore-Colyer, M. J. S. (2017). The Effect of Management Regime on Airborne Respirable Dust Concentrations in Two Different Types of Horse Stable Design. Journal of Equine Veterinary Science, 51: 105-109. Besier, J., Strickler, B., von Niederhäusern, R., & Wyss, U. (2013). Heu oder haylage in der pferdefütterung im vergleich. Agrarforschung Schweiz, 4(6): 264-271. Brazil, T. J., Dagleish, M. P., McGorum, B. C., Dixon, P. M., Haslett, C., & Chilvers, E. R. (2005). 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Update on viral diseases of the equine respiratory tract. Veterinary Clinics of North America: Equine Practice, 31(1): 91-104. Grzela, K., Zagorska, W., & Grzela, T. (2012). Mechanisms of the innate immunity in the respiratory system. Central-European Journal of Immunology, 37(3): 280-285. Humer, E., Hollmann, M., Stögmüller, G., & Zebeli, Q. (2019). Steaming Conditions Enhance Hygienic Quality of the Compromised Equine Hay With Minimal Losses of Nonfiber Carbohydrates. Journal of Equine Veterinary Science, 74: 28-35. Intemann, S., Reckels, B., Schubert, D., Wolf, P., Kamphues, J., & Visscher, C. (2022). The Hygienic Status of Different Forage Types for Horses—A Retrospective Study on Influencing Factors and Associations with Anamnestic Reports. Veterinary Sciences, 9(5): 1-18. Ivester, K. M., Couëtil, L. L., & Zimmerman, N. J. (2014). Investigating the Link between Particulate Exposure and Airway Inflammation in the Horse. Journal of Veterinary Internal Medicine, 28(6): 1653-1665. Johnston, S. L., Goldblatt, D. L., Evans, S. E., Tuvim, M. J., & Dickey, B. F. (2021). Airway Epithelial Innate Immunity. Frontiers in Physiology, 12: 1-9. Leclere, M., Lavoie-Lamoureux, A., & Lavoie, J. P. (2011). Heaves, an asthma-like disease of horses. Respirology, 16(7): 1027-1046. Léguillette, R. (2003). Recurrent airway obstruction - Heaves. Veterinary Clinics of North America: Equine Practice, 19(1): 63-86. Lekeux, P., Art, T., & Hodgson, D. R. (2014). The respiratory system: Anatomy, physiology, and adaptations to exercise and training. In: Hodsen, D. R. & Rose, R.J. (Eds.) The Athletic Horse: Principles and Practice of Equine Sports Medicine: Second Edition. WB Saunders: Philadelphia, USA. Martin, T. R., & Frevert, C. W. (2005). Innate immunity in the lungs. Proceedings of the American Thoracic Society, 2(5): 403-411. Mazan, M. (2022). Equine exercise physiology—challenges to the respiratory system. Animal Frontiers, 12(3): 15-24. McGorum, B. (2002). Environmental Control of Respiratory Disease Do mycotoxigenic fungi cause equine grass sickness. Equine Respiratory Diseases, 1-11. McGorum, B. C., Ellison, J., & Cullen, R. T. (1998). Total and respirable airborne dust endotoxin concentrations in three equine management systems. Equine Veterinary Journal, 30(5): McNamara, K., O’Kiely, P., Whelan, J., Forristal, P. D., & Lenehan, J. J. (2002). Simulated bird damage to the plastic stretch-film surrounding baled silage and its effects on conservation characteristics. Irish Journal of Agricultural and Food Research, 41(1): 29-41. Moore-Colyer, M. J. S. (1996). Effects of soaking hay fodder for horses on dust and mineral content. Animal Science, 63(2): Moore-Colyer, M. J. S., Taylor, J. L. E., & James, R. (2016). The Effect of Steaming and Soaking on the Respirable Particle, Bacteria, Mould, and Nutrient Content in Hay for Horses. Journal of Equine Veterinary Science, 39(): Müller, C. E. (2018). Silage and haylage for horses. 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Séguin, V., Lemauviel-Lavenant, S., Garon, D., Bouchart, V., Gallard, Y., Blanchet, B., Diquelou, S., Personeni, E., Gauduchon, P., & Ourry, A. (2010). Effect of agricultural and environmental factors on the hay characteristics involved in equine respiratory disease. Agriculture, Ecosystems and Environment, 135(3): 206-215. van Erck-Westergren, E., Franklin, S. H., & Bayly, W. M. (2013). Respiratory diseases and their effects on respiratory function and exercise capacity. Equine Veterinary Journal, 45(3): 726-732. Vandenput, S., Duvivier, D. H., Votion, D., Art, T., & Lekeux, P. (1998). Environmental control to maintain stabled COPD horses in clinical remission: Effects on pulmonary function. Equine Veterinary Journal, 30(2): 93-96. Warr, E. M., & Petch, J. L. (1993). Effects of soaking hay on its nutritional quality. Equine Veterinary Education, 5(3): 169-171. Whitsett, J. A., & Alenghat, T. (2015). Respiratory epithelial cells orchestrate pulmonary innate immunity. Nature Immunology, 16(1): 27-35. Wichert, B., Nater, S., Wittenbrink, M. M., Wolf, P., Meyer, K., & Wanner, M. (2008). Judgement of hygienic quality of roughage in horse stables in Switzerland. Journal of Animal Physiology and Animal Nutrition, 92(4): 432-437. Williamson, K. K., & Davis, M. S. (2007). Evidence-Based Respiratory Medicine in Horses. Veterinary Clinics of North America: Equine Practice, 23(2): 215-227. 24 25Moulds and mycotoxins in forages for horses Cecilia E. Müller, PhD Moulds and mycotoxins are undesired in forages as effects on horses and other animals. they may cause irreparable damage to both the horse and Moulds and mycotoxins, if present, cannot be removed human. Moulds produce spores which are associated from the feed. Mouldy forage should be regarded as with the development of chronic airway diseases such as deteriorated and should not be used for feeding any animal equine asthma (Robinson et al., 1996; Riihimäki, 2008). (however a biogas reactor may use it). Prevention of moulds Moulds can also cause mycoses (fungal infections) such in forages is therefore a key issue, as are possibilities to as aspergillosis (Tell, 2005). Mycotoxins are secondary detect moulds in the forage at farm level. metabolites produced by moulds. Mycotoxins may have FIELD FUNGI AND STORAGE FUNGI detrimental health effects on horses, and maximum Moulds in feeds are often categorised into two main limits are given in feed legislations (e.g. EFSA, 2004). groups: field fungi, and storage fungi. The field fungi are Examples of mycotoxins with detrimental effects on present on the standing crop and usually consist of genera RE horses include, but are not limited to, fumonisin B1 P such as Cladosporium, Alternaria and Fusarium, but other AP causing leukoencephalomalacia which is a deadly genera or species can also be present. Although these DE condition, T2-toxin causing oral ulceration, zearalenone L genera are often primarily regarded as a problem for plant CY which is associated with reproductive disorders (Caloni growth and grain quality in cereals, they may also pose a CER & Cortinovis, 2010) and aflatoxins causing liver failure threat to equine health due to formation of mycotoxins in %0 and death (Schurg & Noon, 1979; Scudamore & Livesey, the standing grass crop. Fusarium mycotoxins have been 01 1998; Gallo et al., 2015). Many more mycotoxins exist but found in silage (Driehuis, 2011), hay (Buckley et al., 2007) NO and haylage (Schenck et al., 2019). for most of them there is a scarcity of knowledge of their DETNIR Cecilia E. Müller, PhD, Department of P Animal Nutrition and Management, Swedish University of Agricultural Sciences Cecilia Müller has a PhD in animal nutrition and management and is Associate Professor in equine feed science. She is a Senior lecturer in Equine Nutrition and Management at the Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences (SLU), Uppsala, SWEDEN, and appointed Distinguished University Teacher at SLU. She teaches equine nutrition on bachelor-, master- and PhD-courses and supervises students on all levels in animal science, hippology, veterinary nursing science and veterinary science educational programmes. Research interests comprise forage production and utilisation for horses, hygienic quality of feeds, and equine health and welfare in relation to feeding and nutrition. Cecilia is a member of the Horse Committee at the Faculty of Veterinary Medicine and Animal Science, SLU. She also holds a Professional Diploma in practical equine management from The Horse Industry Professional Committee, Sweden. 24 25WATER ACTIVITY Unit-less variable defined as partial water vapour pressure in equilibrium with the solution, divided by (partial) vapor pressure of pure water at the same temperature. A number between 0 and 1, at 0 no life can exist. Most moulds are more tolerant than bacteria to low water activity. Water activity must be <0 .70 in all dried feeds to avoid mould growth. and water activity where microbes can no longer grow. hay storage fungi comprise e.g. penicillium, aspergillus and can therefore be stored aerobically if it is sufficiently dry at wallemia species and develops during improper storage of harvest or dried using barn-driers, and kept dry during the harvested feeds, where both spores and mycotoxins may entire storage period. dry hay is hygroscopic, and if stored cause health issues in horses (scudamore & livesey, 1998; in a moist environment it absorbs water (also from high samson et al., 2010; gallo et al., 2015). both aspergillus relative humidity in the air) and becomes a perfect substrate and penicillium species, and their mycotoxins, have for mould growth (figure 1). been found in silage (skaar, 1996; o’brien et al., 2007, 2008; driehuis, 2011; wambacq et al., 2016) and haylage as moulds are aerobic (needs oxygen to be able to grow) (schenck et al., 2019), in addition to wallemia sebi in hay and only need moisture to be able to grow in hay, moist (sundberg et al., 2008). oc are risky winter climates with temperatures above 0 preventing mould growth through environments for hay storage. it is necessary to protect the understanding forage conservation dried hay during wintertime to avoid moisture absorption principles and mould growth in the top and outer layers of the hay to prevent growth of moulds in forages it is important batch (sundberg et al., 2008). the easiest and most effective to understand the basics of different forage conservation way to protect the hay is to cover it with straw bales, which methods. forage is commonly conserved as hay, haylage creates a barrier between the hay and the moist air (figure and silage. hay is conserved by drying, silage by ensiling 2). the straw needs to be in place before the time-point and anaerobic storage, and haylage is conserved by semi- when the relative humidity increases in the autumn. in the drying and anaerobic storage (müller, 2018). nordic countries, where hay is generally harvested in june, moisture absorption and mould growth has been registered hay already at the end of august-beginning of september in hay is conserved through removal of water to a unprotected hay (sundberg et al., 2008). sufficiently low dry matter content (at least 840g per kg) figure 1. the white “smoke” in the centre of the photo are mould spores. figure 2. hay stored in a simple uninsulated barn, protected from moist moulds grow quickly in insufficiently dry hay. the spores may cause air using straw bales surrounding the hay batch. wooden pallets on the chronic respiratory diseases in both equines and humans. note! do not floor have been used to provide an air space and avoid moisture from the handle mouldy hay without a protective breathing mask and never feed concrete floor to travel upwards into the hay. credit: c. müller. such hay to any animal. credit: c. müller. 26 27silage and haylage to avoid any leakage of oxygen into the bales (figure 3) silage has a dry matter concentration up to 500g per kg (spörndly et al., 2017). it is important to use a sufficiently forage and is conserved through ensiling, which is a lactic high number of stretch film layers when wrapping the bales: acid fermentation performed by lactic acid bacteria (lab), at least six layers for silage (müller, 2005) and at least eight that are naturally present on the crop (müller, 2005). the layers for haylage (schenck et al., 2019). the higher the dry lactic acid lowers the ph-value, and together with the matter content, and the more mature the crop is at harvest, anaerobic environment created by the wrapping or silo walls, the higher the requirement of the number of stretch film it inhibits mould growth. if the anaerobic seal is broken, the layers to avoid punctures and subsequent mould growth low ph and presence of lactic acid may postpone growth (paillat & gaillard, 2001; o’brien et al., 2007, 2008; keles of fungi but it cannot hinder it completely. therefore, et al., 2009; schenck et al., 2019). increasing dry matter anaerobiosis is required for inhibition of mould growth in content in haylage has recently been reported to increase the silage. haylage can be considered to be “in between” hay risk of finding moulds in general and fusarium mycotoxins and silage, with a dry matter concentration over 500 and up in the forage (schenck et al., 2019). in a recent report from to 840g per kg forage. haylage conservation relies mainly germany it was also found that haylage samples with dry on air-tight storage for avoidance of mould growth (müller, 2018; schenck, 2019), as the higher dry matter content r restricts the lab activity (müller, 2005). some lactic acid ep can be produced in haylage with dry matter contents up ap to about 600g per kg, but in very small amounts and it is del unlikely that it has any major conservation effects. haylage cy can therefore, compared to silage, be regarded as even more cer sensitive to mould growth if the wrapping is not air-tight, %0 as moulds only need oxygen to be able to grow in haylage. 01 n for both silage and haylage bales it is therefore crucial o de figure 4. wrapped bales need to be handled with care to avoid punctures tn in the wrappings, in order to prevent mould growth. store round bales on ir their flat end. credit: c. müller. p matter concentrations between 500 and 700g per kg were less frequently classified as containing too high mould counts compared to samples with>700g dry matter per kg (Intemann et al., 2022). In the same study, haylage samples with dry matter contents >700g per were also positive for Aspergillus detection more often compared to haylage samples with dry matter contents between 500 and 700g per kg (Intemann et al., 2022). A general recommendation for haylage is therefore to not exceed 700g dry matter per kg. Further on, wilting the crop widespread instead of in windrows prior to baling decrease the risk of mould presence in haylage bales due to a faster and more even Figure 3. Visible fungal growth on the surface of wrapped bales are a wilting when widespread (Schenck et al., 2019). Wrapped tell-tale sign that the wrappings have not been air-tight, as these fungi bales should be carefully handled and stored to avoid are aerobic (needs oxygen to be able to grow). Credit: C. Müller. 26 27punctures in the wrapping, and protected from birds and Laboratory analysis of microbial load and mycotoxin wildlife during the storage period. Round bales should be presence in forage can be performed at several feed stored on their flat ends (as there is a higher number of laboratories and provide more information about the stretch film layers there) (Figure 4). hygienic quality of the forage. A sensory examination cannot replace a microbial analysis, but there is a good DETECTION AND ANALYSIS OF MOULDS AND agreement between the results of a sensory examination and MYCOTOXINS a microbial analysis of moulds in haylage (e.g. Intemann A sensory examination of the forage is often the first et al., 2022). This means that if a careful inspection of step in evaluating the hygienic quality of the forage. This haylage is performed and the haylage is judged as having includes to visually inspect the forage, smell it and examine a good hygienic quality (as described above) there will be its structure. Irrespective of the forage type, there should be a high probability that a laboratory analysis of moulds will no visible mould, the smell should be fresh and not dusty, give the same result (Intemann et al., 2022). However, if musty, murky or mouldy, and the forage should have a clear the inspection gives reason to doubt the hygienic quality of structure without lumps or a slimy touch. The colour of the the forage, a laboratory analysis will most likely confirm forage may vary with forage type; a fermented silage (dry it. Visible moulds in hay and wrapped forages (and other matter content below 500g per kg) naturally becomes more feeds) are a sign that the conservation of the forage has not brown than a haylage with higher dry matter content which been optimal, and care should always be taken to not feed may be more green or yellowish. Sun-dried hay is more mouldy feeds to horses, or any other animals, considering the risks of severe disease that are associated with it. yellow than barn-dried hay which is more green. REFERENCES Buckley, T., Creighton, A., & Fogarty, U. (2007). Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins. Irish Veterinary Journal, 60: 231-236. Caloni, F., & Cortinovis, C. (2010). Review: Effects of fusariotoxins in the equine species. The Veterinary Journal, 186: 157-161. Driehuis, F. (2011). Occurrence of mycotoxins in silage. In: Proceedings of the II International Symposium on Forage Quality and Conservation, 16th-19th November 2011, Sao Paolo, Brazil. EFSA (2004). Opinion of the scientific panel on contaminants in the food chain on a request from the commission related to deoxynivalenol, (DON) as undesirable substance in animal feed. EFSA Journal, 73, 1-42. Gallo, A., Giuberti, G., Frisvad, J.C., Bertuzzi, T., & Nielsen, K.F. (2015). Review on mycotoxin issues in ruminants: Occurrence in forages, effects of mycotoxin ingestion on health status and animal performance and practical strategies to counteract their negative effects. Toxins, 7: 3057-3111. Inteman, S., Reckels, B., Schubert, D., Wolf, P., Kamphues, J., & Visscher, C. (2022). The hygienic status of different forage types for horses- A retrospective study on influencing factors and associations with anaemnestic reports. Veterinary Sciences, 9, 226. doi.org/10.3390/vetsci9050226 Keles, G., O'Kiely, P., Lenehan, J.J. & Forristal, P.D. (2009). Conservation characteristics of baled grass silages differing in duration of wilting, bale density and number of layers of plastic stretch-film. Irish Journal of Agricultural and Food Research, 48: 21-34. Müller, C. E. (2005). Fermentation patterns of small-bale silage and haylage produced as a feed for horses. Grass and Forage Science, 60: 109-118. Müller, C.E. (2018). Silage and haylage for horses. Review paper. Grass and Forage Science, 73: 815-827. O’Brien, M., O'Kiely, P., Forristal, P.D., & Fuller, H. (2007). Visible fungal growth on baled grass silage during the winter feeding season in Ireland and silage characteristics associated with the occurrence of fungi. Animal Feed Science and Technology, 139: 234-256. O’Brien, M., O´Kiely, P., Forristal, P.D., & Fuller, H.T. (2008). Fungal contamination of big-bale grass silage on Irish farms: predominant mould and yeast species and features of bales and silage. Grass and Forage Science, 63: 121-137. Paillat, J.M., & Gaillard, F. (2001). PA, Precision Agriculture: Air-tightness of wrapped bales and resistance of polythene stretch film under tropical and temperate conditions. Journal of Agricultural Engineering Research, 79: 15-22. Riihimäki, M. (2008). Inflammatory response in equine airways. Doctoral thesis no. 12/2008. Swedish University of Agricultural Sciences, Uppsala, Sweden. Samson, R.A., Houbraken, J., Frisvad, J.C., Thrane, U., & Andersen, B. (2010). Food and Indoor Fungi. CBS Laboratory Manual series. Utrecht, Netherlands. Schenck, J. (2019). Filamentous fungi in wrapped forages. Doctoral Thesis 2019:69. Swedish University of Agricultural Sciences, Uppsala, Sweden. Schenck, J. S., Müller, C.E., Djurle, A., Jensen, D.F., O’Brien, M., Johansen, A., Rasmussen, P., & Spörndly, R. (2019). Occurrence of filamentous fungi and mycotoxins in wrapped forages in Sweden and Norway and their relation to chemical composition and management. Grass and Forage Science, 74: 613-625. Schurg, W.A., & Noon, T.N. (1979). Experimentally induced aflatoxicosis in mature horses fed naturally contaminated cotton products. In: Proceedings of the Sixth Equine Nutrition Physiology Symposium, College Station, TX, USA. pp 72-73. Scudamore, K.A., & Livesey, C.T. (1998). 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Journal of the Science of Food and Agriculture, 96: 2284-2302. 28 29Industry update: Biosecurity in equine premises Alan Creighton, BSc (Hons) The main part of our work within the Environment and these factors we can lower the incidences of disease, it just Nutrition department at the Irish Equine Centre (IEC) takes the correct mindset and discipline. is working with racing yards, sport horse performance Being proactive is always cheaper than being reactive yards and stud farms where we investigate cases of poor and preventative measures can greatly reduce treatment, performance and respiratory disease outbreaks, design loss of time in development of the animals, labour costs biosecurity systems, as well as mainstream commercial and loss of performance in all equine disciplines. testing of soil, pasture, water, feed and fodder. Our clients BIOSECURITY are here in Ireland, as well as the UK, France, Japan, the Biosecurity can be described as “Providing security RE USA and UAE. P from exposure to harmful pathogens to include parasites, AP We improve the consistency of equine performance by bacteria, viruses and fungi”. DEL implementing best practice in terms of biosecurity, yard C The major disadvantage for modern stud farms and for Y layout, stable design, ventilation, nutrition, and water CE performance horses is the need to travel to competitive R testing, with the goal of providing security from exposure % events, stud farms and sales, where they are mixed with 0 to harmful pathogens such as parasites, bacteria, viruses 01 other animals which will have travelled both nationally and fungi. When talking about biosecurity we promote a NO and internationally. This is often a means of spreading holistic approach. For example, there is no point having a DE infectious respiratory disease (Powell, 1985). A good T good vaccination and stable hygiene programme in place NI vaccination programme, isolation of sick animals, isolation R while allowing the propagation of parasites on the land P of new stock coming onto the farm, or animals returning used for grazing; just as there is no point in following a from sales, helps defend against the spread of viruses and worming programme without paying attention to stable other diseases. hygiene. Poor quality hay, forage, feed and bedding can all impact on the health of any population of horses. In We can protect against bacterial challenge with good financial terms, good biosecurity makes good financial hygiene, isolation, and ensuring the quality of food and sense. If we can minimise disease, we can maximise the water. Fungal spores and hyphae can penetrate the lung and performance of any type of equine premises. also trigger an immune response (Madelin et al., 1991). If animals are in continual contact with pathogenic fungi, Performance horses once stressed will always get sick, their immune system is likely to be challenged which can but there are parameters and exposures within any equine often leave the animal open to secondary disease issues. premises that we can control, such as stocking density, The environment has a major influence on the levels of isolation of new stock, air quality, water quality, stable fungi. We now know that hygiene, ventilation, forage and hygiene, hygiene in indoor exercise areas, food quality bedding quality in a yard have a big impact on how we can and storage. The Environment and Nutrition department at control the exposure to fungi. These environmental factors the IEC has proven time and time again that by improving 28 29play a key role in the development of respiratory diseases. examples of high-risk areas. For example, it’s important Horses when housed indoors can be exposed to high levels that the hay barn doesn’t share the same air space as the of bacteria and moulds which are naturally present in their horses' stabling. Avoid shared air space between stables, bedding and forage (Webster et al., 1987). Respiratory feed and fodder stores, exercise areas, tack rooms, rug infections, for example recurrent airway obstruction (RAO) rooms and vet boxes or treatment rooms. By separating and exercise induced pulmonary haemorrhage (EIPH) units and stores you are minimising the chance of disease are major causes of poor performance in all performance spreading. There is no point in having a biosecurity regime horses. Mild to moderate equine asthma (EA) is associated in place if you then have the manure heap too close to with poor performance, occasional coughing and lower food storage, bedding, walkers or the horses themselves. airway inflammation, often resulting in excess mucus Avoid the possibility of the wind blowing spores, dust and within the tracheobronchial tree and an increase in airway microbes straight back into the horses’ environment. inflammatory cells (Couetil et al., 2016). It is recognised VENTILATION in all ages of horses taking part in all equine performance One of the main factors for controlling the environment disciplines. The impact of respiratory disease will depend in stabling is ventilation. The quality of air entering the not only on the nature and severity of the disease but stable, where and how it exits and the potential influence also on the equestrian discipline performed (Morris & of the air quality in neighbouring stables within a common Seeherman, 1991). airspace should all be considered (Clements & Pirie, Fungi and mycotoxins are recognised as a major cause 2007b). The basic principle of ventilation is that we need of these conditions (Buckley et al., 2007; Carson & cold air to replace warm air and the warm air to remove Ricketts, 2010). The incidence and severity of respiratory moisture, dust, ammonia, spores and microbes when disease are dependent on the everyday interaction between exiting the building. the horse and its environment. The management and housing practices not only have an influence on the horse’s susceptibility to disease but also the levels of respiratory pathogens to which it is exposed (Clarke, 1987). When attempting to control exposure to fungi we need to be aware of how we store forage and feed, where it is stored and the importance of keeping it moisture-free. Performance horses and, in particular, racehorses need a high level of ventilation and stable hygiene. They require spotless exercise areas, walkers and indoor exercise areas, in addition to well-ventilated hygienic boxes. The most Figure 1. Correct ventilation draws warm air and contaminants successful trainers have an unbelievable level of attention up and out of the stable and cooler, fresh air into the stable. Credit: A. Creighton. to detail in this regard. It is important to provide adequate ventilation without YARD LAYOUT draughts at horse height (Sainsbury 1981; Clarke 1987a, Consider how the premises is laid out. Disease will b). We advocate for controllable ventilation at horse height build up and spread in the areas most used by horses and and permanently open ventilation above the horse’s head. areas used by all horses on the farm pose the greatest risk. There must be a vent at the highest point in any building for Walkers, wash bays, vet boxes, transport vehicles are 30 31be fed within 48 hrs once opened during the summer and 72 stale air to exit (Figure 1). Sunlight is a natural disinfectant so plenty of natural light is helpful but not too much so as hrs in the winter. The area where haylage is opened should to make the stable too hot. be clean, uncluttered and disinfected on a regular basis. This area when not maintained becomes heavily contaminated FORAGE AND BEDDING with pathogenic moulds and becomes a vector for mould Mould spores and dust can originate from various contamination of newly opened haylage. Never feed forage sources, such as hay/ haylage, bedding and feed, which are from the same wheel barrow that you muck out into. This substances that the stabled horse encounters on a daily basis. practice is a great way to spread infectious agents. Feed It is under certain conditions that moulds grow unnoticed should be fed from bags in the bin rather than loose in bins. and in turn can produce mycotoxins (see Moulds and The feed house should be a clean, hygienic tidy place. mycotoxins in forages for horses). It is essential to limit the contact that race and performance horses have with moulds The IEC use moulds as a marker organism for a poor- and their mycotoxins. The most common source of mould quality environment and unhygienic conditions. If there are exposure for a horse is forage, and all forage will have some high levels of mould present in the stable environment it mould spores present. These spores can originate from field will also be suitable conditions for many other diseases. mould pre-harvest and storage mould post-harvest (Clarke Consequently, if you control the mould growth you will REP & Raymond, 2001). Nelson et al. (1983) stated that storage also control the growth of many other microbial pathogens. AP is the most important factor that affects physical changes D WATER EL and deterioration in forage quality. C Water quality can be adversely affected by high levels YC It is important to test fodder and bedding prior to use and E of Cryptosporidium (microscopic parasite spread via R % to improve and monitor environmental conditions in which contaminated water), faecal bacteria, iron, aluminium and 001 they are stored. Don’t ever store feed and hay in the same other antagonistic metals. Water quality is particularly NO space as horses. Don’t store good hay near old hay, as the important and influential on performance. Where horses DE are not thriving, with dull coats, we’ve found particularly mould left behind will infect the new hay. Haylage should TNIRP Alan Creighton, BSc (Hons), Head of Environment and Nutrition, Irish Equine Centre Alan was educated at the CBS Naas and received his Honours Degree in Food Science and Nutrition from the Dublin Institute of Technology. He joined the Irish Equine Centre (IEC) in June 1996 to work in the Microbiology unit. He took up the role of the Environmental Scientist in 1999, and as Head of Environment and Nutrition in late 2017. He works with trainers and stud owners at home and internationally on all aspects of equine biosecurity, yard design, nutrition and performance. Alan lectures, writes and speaks on all aspects of equine biosecurity, nutrition and biodiversity for many organisations and media outlets. He is a former show jumper and has a massive interest in all aspects of thoroughbred racing, is a keen breeder and pin hooker. 30 31high levels of metals or antagonistic minerals in the water. ISOLATION UNIT A functioning isolation unit is essential, with no shared air space and as far from the main stabling as possible. It should have its own stock of feed so that staff are not back and forth from the main area. The isolation unit should be a distance from any other stabling and it is advisable to keep mares and foals, yearlings and barren mares separated. Isolate horses coming back from the sales and remember that people can also spread disease (Figure 2). Don’t allow visitors if they are coming straight from other Figure 2. The isolation stable should be kept clean and located away from other facilities. yards, such as vets, farriers etc, unless they have a change of clothes and have washed their hands. The same applies vector for the spread of disease and require constant to staff who might have their own horses at home. Different cleaning and disinfection. wheelbarrows should also be used for straw during an Establish a disinfection routine that everyone is aware outbreak of enteric disease (disease due to intestinal of and make it part of the maintenance routine. Every infection). Remove used bedding from infected stables yard should be power washed a number of times a year. and away from the yard as soon as possible. Never store Preferably use disinfectants that have been approved and mucking out equipment in feed stores. tested against equine specific pathogens. The frequency of GENERAL HYGIENE disinfection will depend on ventilation, age of the buildings, Ensure veterinary staff thoroughly clean equipment dampness, bedding and feed quality. between scopes and wear disposable gloves that are A high level of biosecurity is achievable in all types changed between horses. If the vet or farrier is attending, of equine premises and makes financial sense. Good ensure they attend to any respiratory infected animals last. biosecurity takes a lot of planning and the involvement from In high performance yards it is important to keep everyone on the premises. A good biosecurity policy must competition or older racehorses away from youngstock. be practical for a busy farm or yard. It is about attention to Separate walkers are preferable. Walkers are a serious detail and control over the parameters we can control. REFERENCES Buckley, T., Creighton, A., & Fogarty, U. (2007). Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins, Irish Veterinary Journal, 60(4): 231-236. Clarke, A.E. (1987). Stable environment in relation to the control of respiratory disease. In: Horse Management Ed: J. Hickman Academic Press, London pp 125-174. Clements, J. M., & Pirie, R. S. (2007a). Respirable dust concentrations in equine stables. Part 1: validation of equipment and effect of various management systems. Research in Veterinary Science, 83(2): 256–262. Clements, J.M., & Pirie, R.S. (2007b). ‘Respirable dust concentrations in equine stables. Part 2: The benefits of soaking hay and optimising the environment in a neighbouring stable’, Research in Veterinary Science, 83: 263-8. Couetil, L.L, Cardwell, J.M., Gerber, V., Lavoie, J.P., Leguillette, R., & Richard, E.A. (2016). Inflammatory Airway Disease of Horses, Revised Consensus Statement. Journal of Internal Veterinary Medicine, 30: 503-15. Madelin, T.M., Clarke, A.F., & Mair, T.S. (1991). Prevalence of serum precipitating antibodies in horses to fungal and thermophilic actinomycete antigens: effects of environmental challenge. Equine Veterinary Journal, 23(4): 247‐252. Morris, E.A. & Seeherman, H.J. (1991). Clinical evaluation of poor performance in the racehorse: the results of 275 evaluations. Equine Veterinary Journal, 23: 169-174. Nelson, B. D., Verma, L. R. & Montgomery, C. R. (1983) Effects of storage method on losses and quality changes in round bales of ryegrass and alfalfa hay, Louisiana State University Agricultural Center: Louisiana State University. Powell, D.G. (1985). International movement of horses and its influence on the spread of infection. In: Society for Veterinary Epidemiology and Preventative Medicine, Proceedings, Reading 27-29 March 1985, Ed. Thrusfield, M.V., pp 90-94. Sainsbury, D.W.B., (1981). Ventilation and environment in relation to equine respiratory disease. Equine Veterinary Journal, 13: 167-170. Webster, A.J., Clarke, A.F., Madelin, T.M., & Wathes, C.M. (1987). Air hygiene in stables. 1: effects of stable design, ventilation and management on the concentration of respirable dust. Equine Veterinary Journal, 19(5): 448‐453. 32 33Sleeping patterns in horses Anouk Frieling, MSc Equine Sciences, BSc (Hons) Sleep is an essential behaviour for overall well- and ligaments in the legs, enables the horse to stand for being and is an important component for maintaining prolonged periods and enter light sleep whilst using homeostasis and circadian rhythms in the body (Greening minimum muscle effort (Gussekloo et al., 2011). Because et al., 2021). Horses are prey animals and therefore their equine sleeping patterns are adjusted to be able to respond to sleeping patterns are adjusted to their natural environment danger in their environment, the horse will not rest for long (Greening et al., 2021). If sleeping patterns are disturbed, periods at once but will frequently rest for shorter periods this can affect the body and the brain resulting in various (Oliveira et al., 2022). The NREM phase will be divided illnesses and behavioural disorders (Chung et al., 2018). into about 30 NREM cycles each lasting approximately 3-4 Therefore, to gain more understanding about sleep and minutes (Greening et al., 2021). Generally, horses lie down resting behaviour, sleeping patterns of horses and the effect for a couple of minutes to a couple of hours during the day RE of environmental influences have been studied (Greening (Kelemen et al., 2021). Lying down for at least 30 minutes PAP et al., 2013; Oliveira et al., 2022), to improve and optimise at once is required to enter the REM phase and complete DE equine welfare (Greening et al., 2021). This article will a full sleeping cycle (Kelemen, et al., 2021). Once horses LCY review the sleep patterns of horses, the circadian rhythm enter the REM phase it will last for approximately 3-5 CE involved with sleep, the factors that influence sleep and minutes per cycle (Greening et al., 2021; Kelemen et al., R %0 overall equine welfare, and lastly the consequences of 2021). Altogether, horses sleep approximately 3 hours per 01 sleep disturbances. day (Greening et al., 2021). NO SLEEP PATTERNS AND CIRCADIAN RHYTHMS Circadian rhythms are biological rhythms, including DET sleep, that are regulated within a 24-hour cycle and are N Even though horses are domesticated animals, their IR modulated by day and night (Falcón et al., 2009). Sleeping P sleeping patterns are adjusted to their natural environment patterns are regulated and influenced by the production and behaviour and the danger of predation (Chung et al., of the hormone melatonin, which is synthesised from 2018). Because horses are prey animals they sleep less, circulating tryptophan in the body (Benloucif et al., 2005). and are more vigilant, than predator animals (Hartman & The production of melatonin is modulated by the pineal Greening, 2019). In a full sleeping cycle, there are two gland (Altinsaat et al., 2009), a small endocrine gland in phases of sleep, the non-rapid eye movement phase (NREM) the brain which is regulated by the ‘biological clock’ or the and the rapid eye movement phase (REM) (Greening et al., suprachiasmatic nucleus (SCN), also located in the brain 2021). During the NREM phase rapid eye movements do (Gunata et al., 2020). Production and release of melatonin not occur, but the heart and respiratory rate both decrease is related to photoperiod (Chung et al., 2018), meaning (Oliveira et al., 2022). Once horses enter the REM phase, that the production and secretion of melatonin is inhibited rapid eye movements do occur and loss of muscle tone can during light periods, but is stimulated once it is dark, leading be observed (Oliveira et al., 2022). to the release of melatonin into the bloodstream (Gunata et Usually, horses rest 4-15 hours per day whilst in a al., 2020). Light is perceived through the retinal ganglion standing position (Chung et al., 2018). The passive stay cells in the retina of the eye and once they perceive light or dark from the environment, the cells initiate or inhibit apparatus, a mechanism involving muscles, tendons 32 33Horses stabled on a straw bedding spent significantly the pathway that leads to the production and secretion of more time in lateral recumbency in comparison to horses melatonin in the pineal gland (Ostrin, 2019). Melatonin’s stabled on shavings (Pedersen et al., 2004). This significant main function is to provide the body with information difference between the two bedding materials and lying about the dark periods during the day (Claustrat et al., behaviour was also observed during a study carried out 2005). This information will induce sleep or drowsiness in by Greening et al. (2013). Koster et al. (2017) noted a horses (Chung et al., 2018), and therefore melatonin is the significant difference between straw, shavings and straw key hormone that influences sleep in horses. pellets, with horses spending less time in recumbency on FACTORS THAT HAVE AN EFFECT ON SLEEPING straw pellets in comparison to shavings and straw. BEHAVIOUR AND EQUINE WELFARE Rubber mats are often used to cover the stable floor Equine welfare can be optimised by evaluating the five and serve as bedding material or as a floor base for other domains (nutrition, overall health, environment, behaviour bedding materials such as straw or shavings. Burla et al. and mental state) that can ensure optimal welfare and (2017) observed a significant difference in lying behaviour improve management accordingly (Mellor & Burns, 2020). between horses stabled on rubber mats and horses stabled Studies often use sleep and lying behaviour to measure and on rubber mats covered with bedding materials. Horses assess equine welfare as horses lie down once they feel safe stabled on rubber mats with the bedding material spent and comfortable in their environment (Chung et al., 2018). significantly more time in recumbency in comparison to the As mentioned, recumbency (lying down) is essential to horses that were stabled on plain rubber mats (Burla et al., enter the REM phase of sleep and complete a full sleeping 2017) This suggests that horses prefer a soft and deformable cycle (Auer et al., 2021). Completing a sleeping cycle is surface leading to increased lying behaviour and sleeping important for a range of physiological processes, therefore patterns (Burla et al., 2017; Koster et al., 2017). it supports and optimises overall health, behaviour and the mental state of the horse, making sleep a suitable tool EFFECT OF STABLE SIZE to measure equine welfare (Auer et al., 2021; Greening Stable measurements impact on equiune welfare due et al., 2021). to the influence that stable size has on lying and sleeping behaviour. Raabymagle & Ladewig (2006) analysed the Since domestication, horses have been housed in effect of stable size on lying behaviour of horses. During different environments using varying housing systems the study horses were kept in either a small or large stable (Kelemen et al., 2021). It has been hypothesised that the based on their wither height (Raabymagle & Ladewig, environment and housing systems can have an effect on the sleeping patterns of horses and therefore influence overall welfare (Kelemen et al., 2021). Over recent years, studies have identified the factors that influence sleeping behaviour to create more awareness and optimise equine welfare. EFFECT OF STABLE BEDDING Pedersen et al. (2004) studied the effect of stable bedding on the lying behaviour of horses. There are various materials that function as stable beddings, but commonly used materials are straw or shavings (Figure 1). For this study Pedersen et al. (2004) stabled nine horses on wheat Figure 1. Different bedding in the stable influences the lying behaviour of straw and nine horses on oven-dried shavings and observed horses. Because the lying behaviour is dependent on the type of bedding, the sleeping behaviour is also influenced by bedding. their resting behaviour during a trial period of three weeks. 34 352006) (Equation 1). Results of this study showed that physical discomfort can influence the sleeping patterns horses in the larger stables spent more time recumbent in in horses. comparison to the horses in smaller stables. Throughout the EFFECT OF DIETARY CHANGES trial period, lying behaviour increased in horses that were Dallaire & Ruckebusch (1974) observed the effect of moved from a small stable to a larger stable (Raabymagle & different dietary conditions on the sleeping behaviour Ladewig, 2006). These results demonstrate the importance of housed ponies. Trial ponies first received ad lib hay of suitable stable sizes and the effect it can have on lying to decide the baseline for the study. After establishing a behaviour and sleeping patterns of horses. baseline, hay was replaced with oats. When oats were fed instead of hay, the total recumbency time and time spent asleep increased (Dallaire & Ruckebusch, 1974). It is suggested that this observation is a consequence of the production of gastrointestinal hormones, due to rapidly metabolising oats, which is stimulated due to a satisfied feeling therefore increasing sleeping behaviour (Dallaire & Equation 1. Formulas used during the study conducted by Raabymagle & Ladewig (2006) to establish stable sizes used during the trial period. Ruckebusch, 1974). R SLEEPING DISORDERS EPA EFFECT OF ARTIFICIAL LIGHT Sleeping disorders identified in horses thus far are P D Daylight and darkness have an effect on the production hypersomnia and narcolepsy (Bertone, 2015). Horses ELC of melatonin in the pineal gland and therefore influence diagnosed with hypersomnia spend some time lying YC sleeping patterns. Greening et al. (2021) studied the effects E down, but due to underlying health concerns, are unable R of light on sleeping patterns in horses. During the trial period % to enter the REM phase leading them to experience REM 00 one of the treatment groups was housed in stables with 1 N natural light whilst another treatment group was stabled in O D an environment with artificial fluorescent lights (Greening ET et al., 2021). Both the NREM phase and the REM phase NIRP were significantly reduced in horses that were stabled in an environment with artificial fluorescent lighting, suggesting that artificial lighting in stables can have a negative effect on sleeping patterns (Figure 2). EFFECT OF DISEASE AND PHYSICAL CHALLENGES Disease and physical challenges have been shown to negatively influence the quantity and quality of sleep in humans. Therefore, Oliveira et al. (2022) studied the lying and resting behaviour in hospitalised horses diagnosed with osteoarthritis. Horses with severe osteoarthritis spent less time in recumbency in comparison to horses with milder osteoarthritis (Oliveira et al., 2022). This is likely due to discomfort in flexed joints that horses with severe osteoarthritis experience when they try to lie down (Oliveira Figure 2. The type of artificial light has a significant effect on the et al., 2022). Due to decreased time spent in recumbency, sleeping behaviour of horses. This is possibly linked to the production horses are unable to enter the REM phase, thus disease or and inhibition of melatonin which relies on light and dark during the day. 34 35sleep deficiency (Lyle & Keen, 2010). Narcolepsy has been diagnosed in horses experiencing excessive daytime sleepiness and lack of, or abnormal, REM sleep (Lyle & Keen, 2010). Abnormal REM sleep is characterised by cataplexy (loss of muscle tone and reflexes) (Lyle & Keen, 2010). Although these disorders have been identified, there is limited research available about the effects these disorders have on equine behaviour, health and activity. But, due to the decreased quality of sleep, it is suggested Figure 3. If horses experience sleep deficiency, it is possible that they that it affects overall equine welfare. unintentionally enter the REM sleep while standing. This can result in horses collapsing as a horse requires to lie down to enter REM sleep. Greening & McBride (2022) recently published a more would collapse leading it to immediately wake up (Williams in-depth article reviewing the relationship between sleeping et al., 2008). Once the underlying issue of the lying and behaviour and equine welfare. sleeping behaviour of the horse was identified and resolved, CONSEQUENCES OF SLEEP DISTURBANCES ON the horse slept for a prolonged period to compensate for EQUINE WELFARE the lack of sleep during the trial period (Williams et al., As explained previously, lying and sleeping behaviour 2008). If the condition becomes chronic horses can struggle are influenced by physical distress and environmental to maintain a healthy body condition and also experience insecurities (Bertone, 2006). If the physical distress and decreased attitude and poor performance (Bertone, 2015). environmental insecurities remain for a prolonged period, It is suggested that sleep deprived horses can develop the sleeping patterns are influenced and horses can start stereotypic or abnormal behaviour (Chung et al., 2018). to experience sleep deficiency (Bertone, 2006). When Stereotypic behaviours are often characterised as box- horses experience sleep deficiency, specifically REM sleep walking, weaving or crib-biting (Cooper & McGreevy, deficiency, it can result in various health and mental issues 2007). The behaviour is repetitive and does not seem to have (Greening & McBride, 2022). a specific goal (Hausberger et al., 2007), and horses often Severe REM sleep deficiency, due to lack of recumbency, display stereotypical behaviour due to being in a stressful can result in horses collapsing as they unintentionally enter environment for a prolonged period (Briefer Freymond et the REM sleep phase whilst standing (Bertone, 2015). al., 2020). Currently, studies that have identified the effects Williams et al. (2008) evaluated the normal response of sleep deprivation on behaviour are scarce therefore there of horses to environmental stress. During the study, is an interest in further investigating this area (Greening & recumbency was not observed in one of the trial horses McBride, 2022). (Williams et al., 2008). Therefore, if the horse entered REM SUMMARY sleep it occurred while in a standing position (Williams et Sleep is an essential behaviour for various functions in al., 2008) (Figure 3). A dramatic loss of muscle tone was the body and overall well-being of the horse. There are two observed when the horse entered the REM phase and the phases of sleep the NREM phase and REM phase. Horses horse’s head leaned forward to the ground (Williams et al., sleep for approximately 3 hours per day divided into 30 2008). Because the limbs are unable to support the horse NREM cycles each lasting for approximately 3-5 minutes in a standing position once it enters REM sleep, the horse and the REM phase which usually lasts 3-4 minutes. Sleep 36 37is part of the circadian rhythm in the body and is regulated and sleep once they feel comfortable in their environment. by the hormone melatonin which is secreted from the pineal Environmental differences and different housing systems gland. The production of melatonin is regulated by light can have an effect on the lying and sleeping behaviour and dark which is perceived through retinal ganglion cells of the horse and therefore also on the overall welfare. If in the retina of the eye. Melatonin is therefore a key factor horses remain in a condition where they are unable to sleep in horses' sleeping patterns. Lying and sleeping behaviour regularly they can become sleep deprived. This can have a is often used to measure equine welfare as horses lie down negative effect on their behaviour and their welfare. REFERENCES Altinsaat, C. C., Üner, A. G., Sulu, N., & ErgüN, A. (2009). Seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horse. Ankara Universitesi Veteriner Fakultesi Dergisi, 56(1): 19-24. Auer, U., Kelemen, Z., Engl, V., & Jenner, F. (2021). Activity time budgets—a potential tool to monitor equine welfare? Animals, 11(3): 1-12. Benloucif, S., Guico, M. J., Reid, K. J., Wolfe, L. F., L’Hermite-Balériaux, M., & Zee, P. C. (2005). Stability of melatonin and temperature as circadian phase markers and their relation to sleep times in humans. Journal of Biological Rhythms, 20(2): 178-188. Bertone, J. J. (2006). Excessive Drowsiness Secondary to Recumbent Sleep Deprivation in Two Horses. Veterinary Clinics of North America: Equine Practice, 22(1): 157-162. Bertone, J. J. (2015). Chapter 10 - Sleep and Sleep Disorders in Horses. In Furr, M., Reed, S., (Eds.) Equine Neurology: Second Edition. John Wiley & Sons Inc.: New York, USA. Briefer Freymond, S., Beuret, S., Ruet, A., Zuberbühler, K., Bachmann, I., & Briefer, E. F. (2020). Stereotypic behaviour in horses lowers stress but not spatial learning performance. Applied Animal Behaviour Science, 232(2020): 1-11. R Burla, J. B., Rufener, C., Bachmann, I., Gygax, L., Patt, A., & Hillmann, E. (2017). Space allowance of the littered area affects lying behavior in group- EP housed horses. Frontiers in Veterinary Science, 4(23): 1-12. AP Chung, E. L. T., Khairuddin, N. H., Azizan, T. R. P. T., & Adamu, L. (2018). Sleeping patterns of horses in selected local horse stables in Malaysia. D Journal of Veterinary Behavior, 26(2018): 1-4. E Claustrat, B., Brun, J., & Chazot, G. (2005). The basic physiology and pathophysiology of melatonin. Sleep Medicine Reviews, 9(1): 11-24. LC Cooper, J., & McGreevy, P. (2007). Stereotypic Behaviour in the Stabled Horse: Causes, Effects and Prevention without Compromising Horse YC Welfare. In: Waran, N (Eds.) The Welfare of Horses. Animal Welfare, volume 1. Springer: Dordrecht, the Netherlands. E Dallaire, A., & Ruckebusch, Y. (1974). Sleep and wakefulness in the housed pony under different dietary conditions. Canadian Journal of Comparative R Medicine. 38(1): 65-71. %0 Falcón, J., Besseau, L., Fuentès, M., Sauzet, S., Magnanou, E., & Boeuf, G. (2009). Structural and functional evolution of the pineal melatonin system 01 in vertebrates. Annals of the New York Academy of Sciences, 1163: 101-111. N Greening, L., Downing, J., Amiouny, D., Lekang, L., & McBride, S. (2021). The effect of altering routine husbandry factors on sleep duration and O memory consolidation in the horse. Applied Animal Behaviour Science, 236(2021): 1-8. D Greening, L., & McBride, S. (2022). A Review of Equine Sleep: Implications for Equine Welfare. Frontiers in Veterinary Science, 9: 1-22. ET Greening, L., Shenton, V., Wilcockson, K., & Swanson, J. (2013). Investigating duration of nocturnal ingestive and sleep behaviors of horses bedded N on straw versus shavings. Journal of Veterinary Behavior: Clinical Applications and Research, 8(2): 82-86. IR Gunata, M., Parlakpinar, H., & Acet, H. A. (2020). Melatonin: A review of its potential functions and effects on neurological diseases. Revue P Neurologique, 176(3): 148-165. Gussekloo, S. W. S., Lankester, J., Kersten, W., & Back, W. (2011). Effect of differences in tendon properties on functionality of the passive stay apparatus in horses. American Journal of Veterinary Research, 72(4): 474-483. Hartman, N., & Greening, L. M. (2019). A Preliminary Study Investigating the Influence of Auditory Stimulation on the Occurrence of Nocturnal Equine Sleep-Related Behavior in Stabled Horses. Journal of Equine Veterinary Science, 82(2019): 1-4. Hausberger, M., Gautier, E., Müller, C., & Jego, P. (2007). Lower learning abilities in stereotypic horses. Applied Animal Behaviour Science, 107(3–4): 299-306. Kelemen, Z., Grimm, H., Long, M., Auer, U., & Jenner, F. (2021). Recumbency as an equine welfare indicator in geriatric horses and horses with chronic orthopaedic disease. Animals, 11(11): 3189. Kelemen, Z., Grimm, H., Vogl, C., Long, M., Cavalleri, J. M. V., Auer, U., & Jenner, F. (2021). Equine activity time budgets: The effect of housing and management conditions on geriatric horses and horses with chronic orthopaedic disease. Animals, 11(7): 1867. Koster, J., Hoffmann, G., Bockisch, F. J., Kreimeier, P., Koster, J. R., & Feige, K. (2017). Lying behaviour of horses depending on the bedding material in individual housing in boxes with or without adjacent pen. Pferdeheilkunde, 33(1): 43-51. Lyle, C. H., & Keen, J. A. (2010). Episodic collapse in the horse. Equine Veterinary Education, 22(11): 576-586. Mellor, D. J., & Burns, M. (2020). Using the Five Domains Model to develop welfare assessment guidelines for Thoroughbred horses in New Zealand. New Zealand Veterinary Journal, 68(3): 150-156. Oliveira, T., Santos, A., Silva, J., Trindade, P., Yamada, A., Jaramillo, F., Silva, L., & Baccarin, R. (2022). Hospitalisation and Disease Severity Alter the Resting Pattern of Horses. Journal of Equine Veterinary Science, 110(2022): 1-6. Ostrin, L. A. (2019). Ocular and systemic melatonin and the influence of light exposure. Clinical and Experimental Optometry, 102(2): 99-108. Pedersen, G. R., Søndergaard, E., & Ladewig, J. (2004). The influence of bedding on the time horses spend recumbent. Journal of Equine Veterinary Science, 24(4): 153-158. Raabymagle, P., & Ladewig, J. (2006). Lying behavior in horses in relation to box size. Journal of Equine Veterinary Science, 26(1): 1-15. Williams, D. C., Aleman, M., Holliday, T. A., Fletcher, D. J., Tharp, B., Kass, P. H., Steffey, E. P., & LeCouteur, R. A. (2008). Qualitative and quantitative characteristics of the electroencephalogram in normal horses during spontaneous drowsiness and sleep. Journal of Veterinary Internal Medicine, 22(3): 44-45. 36 37Glossary Aerobic A process requiring oxygen. Ambient temperature The air temperature surrounding an object. Anaerobic A process requiring an absence of oxygen. Circadian Biological processes occurring naturally on a 24-hour cycle. Creatine kinase An enzyme found in skeletal muscles, the heart muscles and the brain. Degeneration Loss of function of cells, tissues or organs. Dopaminergic Relating to dopamine, e.g. dopaminergic neurons secrete dopamine. Tissues that make and release hormones that travel in the blood and control actions of Endocrine other cells or organs. Epithelium A thin coating of tissue that covers organs, glands and other structures in the body. Erosion Gradual destruction of tissue by physical or chemical action. A group of living things ranking below the family in classification and is made of one Genera or more species. Glandular Relating or involving glands or gland cells. Hyperglycaemia Higher than normal amount of glucose in the blood. Hyperinsulinemia Higher than normal amount of insulin in the blood. Branches found in fungi which serve as structures important for growth in fungi. These Hyphae branches together are referred to as mycelium. Any combination of resting hyperinsulinemia, postprandial hyperinsulinemia Insulin dysregulation (response to oral sugar test or consumed feeds), or tissue insulin resistance (hepatic and / or peripheral)* Lactate dehydrogenase An enzyme that supports cellular respiration. Lesions A region in an organ or tissue that suffered damage due to disease or injury. Leukoencephalomalacia A neurotoxic disease in horses. Mycotoxins Toxic substances produced by fungi. Neurosecretory cells A type of nerve cell (neuron) that secretes neurohormones. Neutrophils A type of white blood cell providing immune defences. Omeprazole A medicine inhibiting the secretion of gastric acid. Pathophysiology A physiological process associated with injury or disease. Prophylactic Medicine intended to prevent disease. Pulmonary haemorrhage An acute bleeding in the respiratory tract. Respiratory muscles Skeletal muscles that pump air in and out of the lungs. Squamous A thin layer of epithelium cells that look like scales. * Equine Endocrinology Group (2020). Recommendations for the Diagnosis and Treatment of Equine Metabolic Syndrome (EMS). 38 39Hungry for knowledge? REPAP DELCYC To get every edition of The JEN ER to your inbox for free, sign up today at %001 feedmark.com/JEN NO DETNIRP You will receive no marketing literature, and you will be the first to receive The JEN! 38 3943 YEARS AT THE CENTRE OF EQUINE NUTRITION 40 PB