The Journal for Equine Nutrition - Winter '21

Issue 3 The Journal for WINTeR 2021 Equine Nutrition ® Feedmark Feeding programme considerations Dr. Stephanie Wood The importance of regular dental care Andrew Peffers BVetMed Keeping horses warm this winter: an insight into thermogregulation and the horse's requirements Rebecca Allan Nutrient spotlight: essential fatty acids Dr. Stephanie Wood Maintaining skin health during wet, cold weather Orsolya Losonci 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] Feedmark Ltd, Church Farm, St Cross South Contributors Elmham, Harleston, Norfolk, IP20 0NY With special thanks to Andrew Peffers, Rebecca Allan and Orsolya Losonci Whilst every care has been taken in compiling this publication Production & Design The JEN shall not be made liable for any inaccuracies therein. Penny Church and Gemma Hill The opinions expressed in this publication are not necessarily [email protected] those of the Editor/Publisher. 2 3Welcome Welcome to the winter issue of the JEN. This issue is part of their digestive system. The article has excellent timed to support you and your horses through the cold, photographs of common dental issues affecting equids, wet seasonal weather and provide some interesting reading providing a look inside the horse’s mouth, a world many of during the longer evenings. The articles are full of practical us do not get to see! The importance of effective teeth and information and recommendations to help you manage chewing is highlighted in the next article on how to keep your horses during these challenging months. your horse warm this winter by Rebecca Allan, Assistant Nutritionist at Feedmark. Rebecca discusses the science Winter can be a time when dietary changes are needed, behind thermoregulation and how feeding forage is one either due to changes in the horse’s condition, health or of the most effective ways of keeping your horse warm exercise level, or due to changes in management as a result due to the microbial fermentation used to process it. The of restricted field turnout, reduced daylight hours and time article also reviews water intake and the effects of rugging, available to do the horses. Knowing what dietary changes making it extremely timely. are most appropriate can be daunting, especially if you The fourth article reviews what we know about essential look at the range of feeds and supplements available that fatty acids in a nutrient spotlight. Feeding fat is common all appear suitable for your horse. The first article provides practice to increase energy intake and help horses maintain a step-by-step guide on feeding programme considerations, REP body weight or provide a slow-release energy source, outlining the factors to consider when deciding what to feed AP however the type of fat that is fed should be considered if your horse. I wrote this article as I feel it is important that DE beneficial anti-inflammatory effects are desired. The article the overall aim of a feeding programme is identified, and LC reviews fatty acid structure, nomenclature and beneficial each individual animal’s requirements are assessed, before YC effects. The final article is also extremely timely, with any feeds are even reviewed. This helps to reduce the ER Orsolya Losonci discussing how to maintain skin health likelihood of selecting the wrong feedstuffs simply because %0 during wet, cold weather. Common skin issues, mud fever they are promoted or fed by others on your yard, and should 01 and rain scald, are discussed and recommendations on prevent having to make repeated dietary changes, and may NO prevention and treatment provided. even save you money as you will have selected the most D appropriate feedstuffs in the first instance. E I hope you enjoy reading this issue and that it provides TNI advice and tips that you can use to make the winter months The second article by Andrew Peffers of North Wales RP that little bit easier. Equine Dental Clinic, who is an Advanced Veterinary Practitioner in Equine Dentistry, very clearly explains the importance of regular dental care. Dental care is vital as everything we feed must be chewed to some degree before being swallowed, making the horse’s teeth a key Dr. Stephanie Wood Editor CONTENTS 4 18 Feeding programme considerations Nutrient spotlight: essential fatty acids 8 29 The importance of regular dental care Maintaining skin health during wet, cold weather 12 35 Keeping horses warm this winter: an insight into Glossary thermoregulation and the horse's requirements 2 3Feeding programme considerations Dr. Stephanie Wood, PhD Equine Nutrition, PgDip, BSc (Hons), RNutr (Animal), R.Anim.Tech Feeding horses seems to have become a complicated they were fed in their natural form. The term ration refers business. An internet search with the term ‘how to feed to the amount of feed given to the horse, in total and of my horse’ produced over 140 million results, showing each individual feedstuff. Some horses may be fed a forage how there is now a vast amount of information available to only diet meaning that the total ration is also provided as owners and carers of horses. Not all of those search results forage, whereas others may have a diet that comprises of will be relevant, but if we also add in information provided forage, concentrate feed and a supplement. The total ration in magazines, videos, from equine feed and supplement for these horses is the total amount of feed consumed on producers, from animal welfare charities, vets, instructors, a daily basis, made up of the individual rations (amounts) farriers and the multitude of social media groups dedicated for each feed type. When deciding what to feed your horse, to the topic of equine health, nutrition and management, the feeds selected (diet) and the amounts fed (ration) need it is easy to see why people can become confused and to be considered in combination to ensure their nutrient overwhelmed by the task of feeding their horse. Many of requirements are met. these sources provide correct information that is based on Outlined below are some of the steps to take when sound scientific research and practical experience, however developing your horse’s diet and ration. some information, particularly that from unverified sources, IDENTIFY THE OVERALL AIM OF THE FEEDING contains inaccuracies and recommends inappropriate PROGRAMME feeds or rations. This short article outlines the key points As mentioned above, it is important to know the aim to consider when deciding what to feed your horse and in of your horse’s feeding programme. This could be as what quantities. simple as keeping everything the same, or it could be more Two terms that are often used when discussing equine complicated with the aim of improving a specific health nutrition are diet and ration. Diet refers to the feedstuffs the issue or reducing your horse’s body weight whilst ensuring animal is eating. Grass, hay, oats, sugar beet, competition they have enough energy to perform more demanding mix, and supplements are all examples of feedstuffs. The exercise. Identifying the aim of feeding programmes is feeds consumed supply the nutrients that the horse needs what makes them individual to each horse and leads to to sustain life and perform any additional activities, such an endless answer to the initial question of ‘how to feed as heal, grow, reproduce, or perform exercise. The level of my horse’. This is what makes the subject of nutrition so nutrients within feeds and the availability of those nutrients challenging, as there is no single diet and ration that will to the horse, varies depending on the feed type, the nutrient work for all horses. There are however general principles profile, the combination of feeds fed, and the form in which that support the horse’s physical and behavioural wellbeing feeds are given. For example, forages are generally higher which are outlined below. Taking the time to identify what in structural carbohydrates (fibre) and lower in soluble you want to achieve through the feeding programme will carbohydrates (starch and sugars) and protein, compared to help to keep you focused on the overall aim as you examine cereal grains, and processing feedstuffs (cooking, crushing, grinding) generally makes them more digestible than if your horse’s more specific requirements. 4 5or who maintain a healthy weight easily, feeding forages ad libitum is an easy way to satisfy this physiological and behavioural requirement for trickle feeding. Additional feedstuffs to supply protein, vitamins and minerals, can then be added in measured amounts to satisfy requirements. Equids that are overweight or gain weight easily can be more challenging unless the right feedstuffs are selected. Horses should eat between 2% and 2.5% of their body Figure 1. Feeding programmes should be individual to each horse, weight per day on a dry matter (DM) basis (NRC, 2007), tailored to their specific requirements. although many can consume much higher amounts than this. For a 425kg horse this equates to 8.5kg of DM each CONSIDER YOUR HORSE'S PHYSIOLOGICAL AND day. An overweight body condition shows that energy is BEHAVIOURAL REQUIREMENTS being consumed in excess, therefore the balance in these Equids have a gastrointestinal tract (GIT) developed to situations is feeding enough food to satisfy the daily DM process large amounts of plant material that is of relatively requirement, without feeding excess energy. Selection of low nutritional value. The article Your horse’s gut: RE appropriate feedstuffs holds the key. If feedstuffs that are gastrointestinal structure and function describes in detail PAP low in energy are selected, then enough can be fed to allow the equine GIT structure, the importance of chewing and DEL trickle feeding. Low energy chaffs or chopped straw are feeding fibrous feedstuffs, and some of the consequences CY just two examples of potential feeds for such situations, but of feeding cereal grains in large amounts. When developing CER these must still be fed in appropriate amounts to prevent equine feeding programmes, it is important to account for %0 excess intakes. This is just one example of how diet and 0 GIT structure and the processes involved in the breakdown 1 N ration must both be considered when deciding your horse’s of ingested food. The trickle feeding strategy of equids also O D feeding programme. needs to be considered, as this has consequences on GIT ETN health and behaviour. Grazing and chewing are appetitive I This is also the time to consider specific health issues RP behaviours in equids, meaning that all equids have a natural your horse has as these can influence what feeds can be desire to perform these behaviours to satisfy a bodily fed, what feeds need to be avoided, and the form of feeds. need (Roberts et al., 2017). If these behaviours cannot Dental health greatly influences the types of feeds that can be performed due to not having access to grass or forage be grasped and chewed, and so must be considered (see The (low forage diet or restricted eating time), other behaviours importance of regular dental care). The most nutritious feed replace the desired behaviour as the horse is still motivated is no good if it cannot be chewed to a small enough size to to perform such behaviour. This can lead to undesirable be swallowed. Horses affected by certain health issues such behaviours such as crib biting, windsucking and wood as insulin resistance or polysaccharide storage myopathy chewing which then become habitual behaviours, making (PSSM) benefit from diets that are low in starch and sugar them extremely difficult to correct even when access to (Naylor, 2015; Durham et al., 2019), whilst those with forage or grazing permits normal behaviour (Roberts et al., respiratory issues benefit from low-dust forages, meaning 2017). As such, reducing the likelihood of such behaviours that hay often requires soaking or steaming (Invester et al., developing in the first instance is preferred, through 2014; Moore-Colyer et al., 2016). Consideration of these management and feeding practices that enable grazing and factors combined with the overall feeding aim enables chewing for most of the day. For equids that are underweight suitable feedstuffs to be identified. 4 5EVALUATE THE SETTING AND FACILITIES YOU maintain, or lose weight, however it is important to record HAVE AVAILABLE body weight and fat stores so changes in these parameters An often overlooked consideration when developing can be monitored over time, and the feeding programme feeding programmes is the setup of the facilities where the adjusted accordingly. Accurately measuring body weight horses live, the management routines to be followed and can be achieved with access to a weigh scale which many access to the desired feedstuffs. If your own commitments owners do not have. Alternatively, an equine weigh tape or the horse’s routine only permit twice a day feeding, then provides an estimate of body weight. The accuracy of weigh- there needs to be consideration of how to prolong eating tapes varies depending on the frame of the horse, often time to enable trickle feeding for the period between feeds. underestimating body weight. Despite these inaccuracies, Similarly, if hay needs to be soaked or steamed to remove weigh-tapes provide a better alternative than a best guess dust yet there is no water supply or temperatures are below and are useful in identifying increases and decreases in freezing, feeding haylage may be more practical. Being body weight. Knowing your horse’s body weight enables able to source your preferred feedstuffs is also important to the amount of feed (ration) to be calculated correctly as all ensure a consistent diet can be fed. If the local feed merchant feeding recommendations are based on body weight. is your only option for purchasing feed, and they only Knowing if a change in fat stores is needed enables stock certain brands, then selecting a feed from that range feeds with an appropriate energy content to be selected. will ensure continued supply. Alternatively, if you live in Remembering that horses should consume 2% - 2.5% of an area where feed can be delivered then ordering online their body weight per day as DM, for horses that need to increases the range of feedstuffs you can choose from. gain weight, offering more energy dense feeds enables What is important is that the diet can remain consistent as them to consume enough energy within their daily appetite. sudden dietary changes can cause digestive upset. Simply offering more of a lower energy feed does not result in weight gain as they are physically unable to eat KNOW YOUR BUDGET enough to gain weight. Similarly, feeding a high energy Continuing the theme of consistency, it is important feed to overweight horses leads to weight gain as they eat to select feedstuffs that you can continue feeding for a to satisfy their DM requirements, or the amount they can prolonged period of time. This means they need to be within eat must be severely restricted to limit energy intake, but your budget. Bulk buying is generally cheaper so long as with a negative effect on their GIT health and behaviour. the feed can be stored correctly and it can be fed before it Selecting feeds that are designed for the purpose of the goes out of date. Changing feed brands, even between feeds feeding programme is a good place to begin as these allow with the same or similar name, can cause digestive upset as you to feed the manufacturer’s recommend daily amount, the microbial population within the GIT has not had time to adapt to differences in the ingredients and formulations of which for feeds containing vitamins and minerals, will also feeds that may initially appear the same. provide the correct amounts of these nutrients to balance the diet. If you are unsure about which feeds are most ASSESS YOUR HORSE'S BODY WEIGHT AND suitable, contact a nutrition professional who will support FAT STORES you in selecting the most appropriate feeds for your horse. At this point, the aim of the feeding programme, the horse’s individual requirements and how the feeds are FORAGE FIRST, THEN ADD IN ADDITIONAL going to be fed should all have been identified. It is now NUTRIENTS important to assess the horse’s body weight and fat stores. Forage should be the main feedstuff in every horse’s You may already have identified if they need to gain, feeding programme, regardless of whether they are a top- 6 7level performance horse or retired and living leisurely in a at this stage. The need for supplements should have been identified when considering your horse’s physiological and field. As previously explained, forage provides fibre which behavioural requirements. Suitable supplements designed is needed for healthy GIT function, particularly hindgut for that specific purpose can then be selected. There are function, and to satisfy the need to chew. Fermentation now options to combine individual supplements in tailor- of fibre also provides slow-release energy, enabling some made, bespoke formulations calculated to your horse’s horses to meet their energy requirements from a forage specific requirements. Such options simplify feeding, which only diet. The process of fermentation also produces is helpful for those short on time or based on livery yards considerable heat which the horse can use to help maintain where others are responsible for making up and giving body temperature during periods of cold weather. Providing feeds to your horse. What is important for all supplements as much of your horse’s daily ration as forage is advised, is that they are fed for a specific reason and not because with additional feedstuffs added in to compliment the forage. other horses have them in their diet. This ensures the Such additions include a vitamin and mineral supply as the supplement can have the effect it was developed to have level of these nutrients varies in grass and reduces after and prevent unnecessary feedstuffs being included in the grass has been cut and dried to produce preserved forages feeding programme. (Richards et al., 2021) (see Forage options for horses). RE Options for supplying vitamins and minerals include P SUMMARY AP vitamin and mineral supplements, balancers (vitamins and D Deciding what to feed your horse can seem daunting EL minerals plus a protein source), chaffs containing a vitamin C and is made even more challenging by the vast amount of Y and mineral pellet, and concentrate feeds. The amount of CE information on the subject and the extensive number of R additional energy and protein your horse needs should guide % feedstuffs on the market. Ensuring you identify the key aims 00 your choice of vitamin and mineral supply. If your horse 1 and requirements of the feeding programme is essential N requires more energy than the forage can supply, you could O to enable correct feeds to be selected. Manufacturers of D select a concentrate feed to provide the energy, protein, E quality equine feeds and supplements provide guidance TN vitamins and minerals. In contrast, for horses able to meet I on the amounts that should be fed, although there is still RP their energy requirements from forage, then a balancer or a requirement to assess your horse regularly to determine vitamin and mineral supplement would be more suitable if the feeding programme is suitable and if any changes as these provide very small amounts of energy. For horses are needed. Speaking to a qualified equine nutritionist, sensitive to cereal grains but requiring more energy, oil, or preferably one registered with the Association for Nutrition a high-fat feed such as linseed, can be added to the diet (able to use the title RNutr Animal), is advised as they alongside the forage and vitamin and mineral supplement. will help guide your choice of feeds and supplement and calculate the correct ration for your horse. Supplements for specific purposes can also be added REFERENCES 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. Invester, 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: 1653-1665. 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: 62-68. Naylor, R.J. (2015). Polysaccharide storage myopathy – the story so far. Equine Veterinary Journal, 27(8): 414-419. NRC (2007). Nutrient Requirements of Horses, 6th Ed. The National Academies Press, Washington, USA. Richards, N., Nielsen, B.D., & Finno, C.J. (2021). Nutritional and Non-nutritional Aspects of Forage. Veterinary Clinics of North America: Equine Practice, 37(1): 43-61. Roberts, K., Hemmings, A.J., McBride, S.D., & Parker, M.O. (2017). Casual factors of oral versus locomotor stereotypy in the horse. Journal of Veterinary Behaviour, 20: 37-43. 6 7The importance of regular dental care Andrew Peffers BVetMed Cert AVP (Equine Dentistry) BAEDT MRCVS Advanced Practitioner in Equine Dentistry Below is a list of some of the clinical signs that a horse also anisognathic which means the upper jaw is wider than the lower jaw. Therefore, sharp edges form on the outside may exhibit if it has a dental problem: (buccal) edges of the upper teeth and on the inside (lingual) 1. Head tilt edges of the lower teeth. Unfortunately, because horses’ 2. Head tossing or head shaking teeth are confined in a long narrow mouth it is very difficult 3. Bit chewing for horse owners to examine their own horse’s teeth. 4. Fighting the bit or going badly on one rein For this reason, the majority of equine dental problems 5. Dropping food also known as quidding (Figure 1) go unnoticed by horse owners. Post-mortem studies of 6. Weight loss horses’ heads show dental disease is present in over 50% of 7. Drooling, foul breath horses. Whereas the perceived incidence of dental disease 8. Smelly mucopurulent nasal discharge from one nostril as reported by owners is much lower. The conclusion to be 9. Facial swelling drawn from these studies is that dental disease in horses is being underdiagnosed and this is why it is important that 10. Poor performance every horse has their teeth thoroughly examined at least If a horse is exhibiting any of these signs then it would at once a year. the very least require a detailed dental examination straight INCREASED EFFICIENCY OF EATING away. However, the aim with modern dentistry is to prevent A study by Johnson et al. (2017) was conducted to health problems before they occur. Therefore, the minimum measure faecal fibre length pre- and post-dentistry and requirement for each horse is a dental check-up and rasping found there to be a significant decrease in mean faecal at least once every 12 months. fibre length post-dentistry, suggesting increased efficiency of mastication and digestion of fibrous matter. Therefore, it could be concluded that regular dentistry improves eating efficiency. This study also revealed increased faecal fibre lengths in individuals with more severe dental abnormalities. In addition, studies have demonstrated a link between poor dental care and an increased incidence of both choke and colic (Hillyer et al., 2002; Cox et al., 2009). Again, highlighting the importance of regular dental care. DENTAL DISEASES AFFECTING HORSES Figure 1. Balls of partially chewed hay on the floor of a stable from a horse that is quidding this is a classical sign of a horse with a dental problem. EQUINE ODONTOCLASTIC TOOTH RESORPTION AND HYPERCEMENTOSIS (EOTRH) WHY DO HORSE'S TEETH NEED RASPING? This is a disease that primarily affects incisors but can Horses’ teeth are different to human teeth as they are hypsodont, meaning they keep erupting throughout the also affect canines. It affects mostly older horses, generally horse’s life. They erupt by approximately 2mm every year 15 years or above, and its prevalence increases with the age to replace the tooth that is worn down. The horse’s jaw is of the horse. With this disease the incisors are painful and 8 9can become loose and even fracture. If a horse is reluctant to bite a carrot with their incisors this is often an early indicator that the horse has EOTRH. In addition, horses with EOTRH often resent having the dental gag put on for examination of the mouth. Horses with EOTRH show signs of gum inflammation, oedema and recession (Figure 2). Excess calculus (dental plaque) may be laid down on the incisor where the gum has receded. There may also be obvious swelling of the gum caused by excessive cement laid down around the incisor root. In more advanced cases Figure 2. A horse with Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH). draining tracts may be obvious and the incisors become loose. Diagnosis is by taking x-rays of the incisors. Many teeth (311 and 411) (Figures 3 & 4). Left untreated these different treatments have been tried to treat EOTRH hooks can grow so long that they start to dig into the soft including antibiotics, Chlorhexidine antiseptic cream tissues of the opposite jaw and will stop the horse being (Dentisept®), steroids, surgical debridement of the inflamed able to eat (Figure 5). As long as these teeth are rasped gums, intra-oral splinting and even leaches. However, in R every 12 months this will stop these hooks from forming. E the long-term these treatments are generally unsuccessful, PAP STEP MOUTH and the best long-term treatment is to extract any incisors DE This is the term given when a whole tooth becomes that are loose or painful. Owners fear that the horse will LC dominant and is higher than the rest of the teeth in that Y struggle to eat if they have their incisors extracted, however CE the opposite is normally true, and even horses that have had R % all their incisors extracted tend to eat better afterwards. 001 N HOOKS O D In some horses the upper and lower jaws do not align ET exactly. The usual presentation is that the upper jaw is NIR slightly further forward than the lower jaw. Therefore, the P teeth don’t wear down evenly, causing hooks to form on the front (rostral) edge of the first upper cheek teeth (106 Figure 3. A graphic depicting how rostral hooks and caudal ramps can and 206) and the back (caudal) edge of the last lower cheek form when the upper and lower jaws do not align perfectly. Andrew Peffers BVetMed Cert AVP (Equine Dentistry) BAEDT MRCVS Andy Peffers is a qualified veterinary surgeon with over 25 years experience as an equine vet. He is also a qualified Equine Dental Technician and is an Advanced Veterinary Practitioner in Equine Dentistry. In 2015 he set up a specialist equine dentistry service called North Wales Equine Dental Practice. 8 9arcade. This usually happens when a horse has lost a cheek on the lower teeth. Wave mouths are easily corrected if detected early. Horses with early wave mouths should have regular dental checks every 6 months and about 2-3mm should be removed from the dominant teeth each time. Normally within about two to three years of this treatment the cheek teeth arcades start to look normal. SHEAR MOUTH The occlusal (grinding) surface of normal molars is not flat but slopes downwards at an angle of approximately 15 Figure 4. A large upper rostral hook, this was so large it was causing soft tissue trauma on the opposite lower jaw, preventing the horse from eating. degrees from the lingual (tongue) side to the buccal (cheek) side. In a shear mouth this angle can be greater than 45 degrees (Figure 7). Figure 5. Tongue laceration caused by sharp rostral hook shown in figure 4. tooth or had a cheek tooth removed. The opposing tooth has no tooth to wear against and therefore as the crown erupts by about 2-3mm a year, the tooth gets taller by 2-3mm a Figure 6. A graphic depicting a wave mouth. year. Another occasion when a step mouth occurs is when one adult tooth erupts earlier than its opposite tooth. DIASTEMA These horses require dental visits twice a year to A diastema is a gap between two teeth that is not reduce the overgrowth. normally present. Diastemata occur more frequently in WAVE MOUTH the lower jaw than the upper jaw. The most common type A wave mouth can be thought of as an extension of a of diastema is valve diastema; the teeth at the occlusal step mouth. A step mouth occurs when only one tooth in an arcade is dominant; a wave mouth occurs when two or three cheek teeth in an arcade are dominant (Figure 6). The dominant teeth cause excessive wear on the opposing teeth on the opposite arcade. Thus, through excessive wear the opposing teeth become even more reduced. The dominant teeth then have less to wear against and erupt further, becoming even more dominant. So the cycle continues with the wave mouth gradually becoming worse each year. In Figure 7. An example of shear mouth. The arcades on the left of the photograph are shear with table occlusal angles in excess of 45 degrees, most horses with a wave mouth the upper and lower arcade the arcades on the right have a normal table angle. both have some dominant teeth, and some teeth showing excessive wear. The most common pattern is that the upper (chewing surface) are still quite closely opposed, while at 06’s, 07’s, 10’s and 11’s are dominant and the upper 08’s, the gingival (gum) margin the teeth are narrower forming 09’s show excessive wear. The opposite pattern occurs a gap. Thus, these diastemata, when viewed from the side, 10 11are triangular in shape. Food debris is forced through the INFUNDIBULAR CARIES narrow gap at the top by the huge forces of chewing. This Caries are holes or cavities in the hard tissues of teeth, food packs into the bottom of the diastema, but because for example the cement, dentine or enamel. One of the most of the narrow opening at the top it cannot escape and is common sites for caries in the horse is the infundibulum trapped (Figure 8). This trapped food then undergoes (Figure 9). Only maxillary (upper) cheek teeth have bacterial fermentation, releasing acid which damages the infundibulae. The infundibulum is normally filled with gum margin further. Therefore, the gum margins recede, cement. Studies of the infundibulae of maxillary cheek teeth which makes the diastema deeper and it becomes a self- have shown that many are incompletely filled with cement. perpetuating cycle. All diastemata once diagnosed should This is known as cemental hypoplasia and is believed to be treated. Basic treatment involves cleaning and flushing out diastema with picks, forceps and water irrigation. The gum margins are then treated with Chlorhexidine antiseptic cream (Dentisept®). In more advanced cases or in cases where the initial basic treatment has not worked, REPAP DELCYC Figure 9. A grade 3 infundibular caries. ER %0 be a factor in infundibular caries. Another factor is, as in 0 Figure 8. An example of diastemata with food packing. 1 humans, eating foods high in sugar that cause decay of NO the diastema after cleaning can be filled with soft rubbery the cementum. Deep infundibular caries can weaken the DE dental impression putty. Another treatment is to use a T tooth and actually cause the tooth to fracture (Figure 10). NI diastema burr to scallop a groove on the occlusal surface Therefore it is highly recommended to fill infundibular RP of the diastema to ease the pressure on the surface of the caries if they are grade 2 or above. diastema and to prevent food being forced into the gap. The diet of the horse should be altered if possible to avoid haylage and sugary cereal based feeds as both of these have been implicated in the development of diastemata. It is also advisable to avoid short-chopped forage such as Alpha-A and chaff as these short chopped hard fibres can get stuck in the diastemata, and are uncomfortable for the horses and difficult to get out. REFERENCES Figure 10. A tooth that has been extracted as it had fractured down the Cox, R., Burden, F., Gosden, L., Proudman, C., Trawford, A., & Pinchbeck, G. middle as a result of infundibular caries. (2009). Case control study to investigate risk factors for impaction colic in donkeys in the UK. Preventative Veterinary Medicine, 92(3): 179-187. Hillyer, M.H., Taylor, F.G., Proudman, C.J., Edwards, G.B., Smith, J.E., & French, N.P. (2002). Case control study to identify risk factors for simple colonic Hopefully this article has highlighted some of the dental obstruction and distension colic in horses. Equine Veterinary Journal, 34: 455-463 conditions that horses suffer from, and the importance of Johnson, C., Williams, J., & Philips, C. (2017). Effect of Routine Dentistry on Fecal Length in Donkeys. Journal of Equine Veterinary Science, 57: 41-45. regular dental examinations and rasping for all horses. 10 11Keeping horses warm this winter: an insight into thermoregulation and the horse's requirements Rebecca Allan from the cold and huddle together to stay warm (Hetem Winter conditions vary dramatically between various et al., 2007). regions, as does the tolerance of individual horses to changes in temperature, precipitation, and wind. However, Under certain temperatures, horses can maintain warmth. horses are built for survival, being warm-blooded The norm, known as the thermoneutral zone (TNZ), animals, they are able to maintain their internal core defines the range in temperature where the horse regulates temperature within narrow limits despite the changing its body temperature with little or no energy expenditure environmental conditions. They are able to do this due (Christopherson et al., 1986). It achieves the balance to being endothermic, meaning they can produce heat between heat loss and generation through physiological through metabolic processes in their body, enabling them responses only. A mature horse's average TNZ ranges from to maintain their average body temperature (Frappell et al., 5℃ to 25℃ for horses living in mild climates (Morgan, 2008). This article aims to improve the understanding of 1998). However, as every horse is an individual, TNZ will thermal regulation in horses so owners can help their be influenced by the temperatures the horse is acclimatised horses achieve thermal comfort under winter conditions, to. Of note, horses can reach complete acclimatisation in 21 with a specific highlight on nutrition, the use of rugs, days (McCutcheon et al.,1999). clipping, and shelter. One extreme of the TNZ is the lower critical temperature THERMOREGULATION (LCT), known as the lowest temperature in the TNZ Thermoregulation is the process through which (Martin-Rosset et al., 2015). The horse must increase horses control their internal core temperature through metabolic heat production to maintain its average body physiological responses, achieving the balance between temperature as heat loss exceeds heat production. The LCT heat loss and heat production in response to environmental limit in adult horses is usually 5℃ for those in temperate temperature changes (Guthrie et al., 1998). In winter, climates and extends to -15℃ for those adapted to northern conserving heat is the horse's priority. The two primary continental environments with natural unclipped coats physiological responses to decreased temperatures are (McBride et al., 1985; Morgan, 1998). Increased demands cutaneous vasoconstriction which reduces blood flow to the for metabolic heat production will incur energy costs. skin surface and therefore aids heat retention, and through Additional energy costs for horses to remain in thermal piloerection where the horse’s hair stands up to create an comfort have been studied, with comparative results insulating layer of air to maintain heat close to the horse's achieved. McBride et al. (1985) indicated an overall surface (Hines, 2018). Sudden temperature changes also increase in maintenance energy requirements for horses trigger behavioural responses leading horses to seek shelter suddenly exposed to cold environments (0℃ to -40℃). 12 13able to deal with these conditions. Mature horses required an additional 3.4kJ digestible energy (DE) per kilogram of body weight (BW) per every degree Other factors affecting thermoregulation are breed, Celsius drop below the horse's LCT. Similarly, Cymbaluk age, body condition, size, and health condition. Each et al. (1990) established yearlings’ DE intake requirements horse is unique and must be treated as an individual. For to increase from 110kJ per kg/BW to 145kJ per kg/BW example, young, thin, and older horses are less tolerant when exposed to warm (10.9℃) and cold (-5.2℃) ambient of cold environmental conditions than mature horses in temperatures, respectively. This study estimates a 1.3% DE good condition. Increased DE intakes can be counteracted increase for yearling horses per degree Celsius below 0℃. through correct nutritional management by feeding For weight gain, an additional 0.7% DE intake per degree appropriate amounts of forage. Therefore, it is essential to Celsius below 0℃ was calculated. These studies show the make dietary changes for vulnerable horses much sooner importance of providing enough energy for horses to keep than for mature horses in good condition when temperatures warm, and for those that are growing, enough energy to fall to ensure thermal comfort. also achieve optimum growth rate. FEEDING REQUIREMENTS Although air temperature defines TNZ and LCT ranges, Body temperature is maintained by metabolic processes, R it is important to highlight how wind and rain increases EP including the heat provided from nutrient digestion. A thermoregulation requirements. As mentioned, the horses' P D Feeding fibre is the best way to keep your horses warm E coat traps air creating an insulating layer. However, wind LC during winter months. The primary source of high fibre Y will continuously remove the warm air close to the skin CE feed comes from forages such as grass, hay, or haylage. The aiding heat loss. Similarly, rain causes the coat to be R % equine digestive tract is unique because enzymatic digestion 0 continuously flushed with water again contributing to 01 occurs in the foregut and fermentation occurs in the heat loss. Mejdell et al. (2005) performed a 23-day study NO hindgut. The hindgut houses a vast population of microbes on Icelandic horses acclimatised to living outdoors with DE which breaks down feed that was not digested in the small T access to forage and shelter, to investigate their responses NIR intestine, particularly fibrous feeds such as hay or pasture. to cold weather. Results showed the average incidence of P Fibre is converted by microbial fermentation into volatile horses remaining outdoors was 70%. The study recorded air fatty acids which can then be absorbed and utilised by the temperatures of up to -31℃, however, shivering was only horse’s body (Dougal et al., 2013, Merritt et al., 2013). As observed once, on the day where air temperature was 5℃ a by-product of fermentation, metabolic heat is generated and was in combination with heavy rain. A strong tendency helping warm the horse from the inside out and supporting for increased shelter use in response to wind and rain was thermal comfort (Santos et al., 2011). Grain feeds on the also noted. Similarly, Jørgenses et al. (2016) studied horses other hand, are ultimately the reverse of forage and have a in paddocks in Northern coastal climates, who had access high starch and low fibre content. Starch is enzymatically to two shelter compartments. One of the compartments had digested in the foregut, particularly in the small intestine, by infrared lighting increasing warmth. It was reported that the enzyme amylase, where it is broken down into glucose horses spent more time inside shelters on rainy days and for absorption by the horse’s body. However, this process changes from unheated to heated shelter occurred on wet does not produce metabolic heat as a by-product (Merritt et and windy days. These two studies highlight the increase in al. 2013). Overall, bacterial fermentation produces more thermoregulation requirements for horses when faced with wind and rain, as well as the importance of shelter to be heat than enzymatic digestion. Due to this, fibrous feeds 12 13such as hay have a higher heat increment than low-fibre through commercially available feeds that contain higher feeds such as grain (Julliand et al. 2004). This highlights energy grains and/or fats to provide the necessary energy. the importance of forage consumption for your horses to Selecting which feeds are most suitable will depend stay warm during winter months. Nevertheless, it should be on your individual horse’s requirements (see Feeding mentioned that out of the grains, oats, despite being low in programme considerations). fibre, have a higher heat increment than other grains due to Overall, a winter-feeding programme should be their fibrous outer hull (Lindberg, 2013). based on pasture availability and good-quality forage, supplemented with appropriate sources of energy, protein, Regarding consumption, horses are recommended to consume 2 - 2.5% of their BW per day. Maintenance diets should involve around 2% of a horse’s BW per day, whereas older or growing horses should consume 2.5% of their BW on a daily basis. Forage should be the basis of any horse´s diet as it supports their trickle feeding behaviour and keeps their gut healthy. Good quality forage contains a lot of nutrients and may be capable of providing enough energy for healthy horses in maintenance or light work. Also of note is that fibre provides slow-release energy (Hervik et al. 2019), so can be ideal for horses that can become over-excited. Harper et al. (2004) estimated an increase of 10-15% good quality forage to be fed when temperatures drop below freezing level (0℃). Ideally, an unlimited (ad libitum) supply of forage fed at ground level is the best Figure 1. forage is an excellent way of keeping your horses warm this way to meet your horse's behavioural and nutritional winter. requirements during winter when there is an increased vitamins, and minerals. The amount of grain fed should be demand for heat production. Nevertheless, this system calculated based on your horse's condition and workload may not be appropriate for all horses. For example, an and supplemented properly with good quality forage overweight horse would benefit from a restricted intake before grain addition. A diet high in fibre should meet the due to weight loss; in this case, you can ration their daily increased heat demands for your horses during winter, requirement intake and spread it out throughout the day. whereas low fibre diets would not fully support metabolic On the other hand, for young, old, thin, or performance heat increment requirements. horses who are more vulnerable to winter temperatures or have a high energy output due to exercise, forage alone, As crucial as forage consumption is during the although it should be the baseline of their diet, may not winter months, water intake is equally important. When be sufficient to keep them in top condition as they cannot temperatures decrease, dehydration is probably the last consume enough forage to meet their energy requirements. thing on your mind. However, it is imperative to know that horses can become dehydrated at any time of the year, even Therefore, it is recommended to increase calorie intake, 14 15Rebecca Allan Rebecca moved to England from Spain in 2017 to further her education. While undertaking A levels, she completed BHS Qualifications where she developed a keen interest in equine health and nutrition. In 2019 Rebecca started a BSc (Hons) Veterinary Bioscience degree at the University of Surrey. Rebecca is currently on her placement year as an Assistant Nutritionist at Feedmark Ltd. Her aim is to qualify as a Veterinary Bioscientist and progress into Equine Nutrition in the future. at low temperatures during winter months. Kristula et al. (1994) performed a study consisting of two trials to compare ab libitum consumption of ambient WATER INTAKE near-freezing water (ranged from 0℃ to 1℃) and warm R Horses lose water from their body through faeces, E water (46℃ to 49℃ when provided) of 14 ponies. The P urine, sweat and even through exhaling air, as dry cold air AP study concluded that on average, 40% of the ponies drank D increases water loss from the respiratory tract and lungs. EL more warm water compared to ambient, near-freezing C On top of this, forage consumption in winter increases Y water. Warm water refills occurred at 46℃ to 49℃ CE meaning extra water is required for fibre digestion in the R however, most consumption happened when the water was % hindgut. The accepted water requirement for horses is 00 20℃ to 35℃. Based on this study, providing warm water 1 around 60ml/kg/day (Freeman, 2021). Thus, an average N for horses may encourage them to drink and help maintain O horse (500kg) would require approximately 30L of water D hydration levels. E per day as a minimum requirement. In addition, summer TNI Another factor to consider is that low temperatures R grass has moisture levels of approximately 60-80%, P encourage water to freeze, therefore through correct contributing to the horse’s water intake. In contrast, in management water troughs/ buckets should be checked at winter, hay and grain feeds are fed more abundantly due least twice a day to break and remove any ice if water supply to reduced grass availability. These feedstuffs contain less has frozen. Supplying warm water may minimise this risk, than 15% moisture and so poorly contribute to the horse’s although this may not be practical for many owners. daily water intake (Cymbaluk, 2013). Water is necessary for maintaining moisture levels in the horse’s gastrointestinal A common theme associated with winter is the concept system therefore decreased water consumption causes of rugging and clipping horses. Through many years of ingesta to dry up, increasing the risk of impaction evolution, horses have developed a thick winter coat, colic or intestinal blockage (Bihonegn, 2018). Equids tend composed of two hair types: long stiff guard hairs and fine to drink less water throughout the winter months, therefore hairs as an undercoat (Legnani et al., 2017). The long guard it is essential to observe their water intake and encourage hairs help to shed rain whilst the fine hairs help trap warm them to drink if necessary to maintain hydration and reduce air and act as an insulation layer for your horse (Davies, the risks of colic (see Equine Colic and its associated 2018). Additionally, natural oils in horses' coats have water resistance properties (Langlois, 1994). The hairs are also risk factors). 14 15connected to piloerector muscles which allow the hair to a horse with an extremely fluffy coat may benefit from a lower half body clip (trace clip) as sometimes hacking only stand up, magnifying the insulating layer or allowing the once a week makes them sweat excessively. On the other hairs to lie flat, acting as a cooling mechanism. Thus, horses hand, a horse in medium/hard work which would normally are naturally well adapted to cope with winter conditions. benefit from being clipped may not require it if the horse is So, the question arises, to rug or not to rug? thin skinned and doesn´t grow very much of a winter coat. USE OF RUGS AND CLIPPING Overall, every horse is an individual and the combination Mejdell et al. (2016) trained warm-blooded and of workload and coat thickness would determine clipping cold-blooded horses to use simple “sign language” to necessities. However, as clipping removes the horse’s communicate their preferences for wearing rugs. Mejdell natural winter coat, supplementary rugs for protection et al. (2019) tested 23 horses, under differing weather would be required. conditions, for their rug preference. Results suggested Another factor to consider is weight loss. In natural that no horse preferred to wear a rug in sunny spring and situations, horses lose excess fat during winter, so the summer weather, although most asked for a rug in cold, horse starts off lean in spring to cope better with the new wet, and windy conditions. By air temperature, 80-90% of spring grass. Rugging an unclipped overweight horse will the horses preferred to have rugs on at temperatures under prevent weight loss as they will not move around and burn -10℃. As temperatures increased, the horses’ preference fat to stay warm. If your horse is obese and weight loss is for rugs also decreased, and at 20℃, they did not want desired, consider a trace clip as it will increase the amount rugs. On the other hand, 100% of horses chose to of energy your horse needs to keep warm encouraging heat wear a rug in windy, rainy, and chilly conditions. This generation through movement and burning excess fat. study showed horses preferred a rug in wind and SHELTER rain combined with low temperature conditions due to In addition to rugging and clipping, shelter is imperative increased thermal discomfort. and must be accessible whether your horse has a full coat Theoretically, a horse with a good body condition, a or is rugged or clipped. The shelter can naturally occur natural coat, and a good supply of forage would not require through vegetation such as trees or hedges, or be provided a rug under moderate temperature conditions (5℃) as as manufactured enclosures such as field shelters and its own body would be able to generate sufficient heat to stables. These man-made options provide a more permanent maintain an average body temperature. However, as per the management solution for when the weather changes rapidly previous studies, rain and wind cause thermal discomfort; and enables horses to cope with sudden wind and rain. therefore, providing access to shelter with the possibility Overall, it is safe to say, an unclipped horse with access of a rug would be the best option to challenge these to shelter in good body condition with plenty of forage fluctuations in climate. and water would not require a rug, as metabolic heat alone Clipping nowadays is a common practice in winter, it produced by digestion will suffice. However, rugging the minimises sweating and allows horses to dry off quicker unclipped horse depends on rain, wind, sunshine, and after exercise, preventing the development of a chill. each horse’s cold weather threshold as well as owner However, workload is not the only deciding factor when requirements. Horses needing to be ridden after being deciding whether to clip or not. An individual horse’s coat out in the rain would benefit from a rain sheet to keep the also determines whether they need clipping. Generally, a horse in light work would not need clipping, however, saddle area dry. At the same time, fully clipped horses will 16 17need rugs in winter no matter the circumstance due to not intervention to meet feeding requirements for each horse having their natural winter coat for protection. is required. Providing horses with the necessary forage is fundamental to support their internal heating mechanism SUMMARY and ensuring water intake requirements are met is crucial Horses will experience differing thermal challenges to prevent dehydration and colic. Additionally, a rug is during the winter months. Lower temperature combined a helpful supplement for more vulnerable horses and with wind and rain are very demanding, and the clipped horses as it provides extra protection from cold management of horses throughout this period must be temperatures. However, it is imperative for horses to have based on thermoregulation principles, facilitating horses access to shelter during winter months to be able to cope to maintain their internal core temperature. Once the LCT limit is reached, energy demands increase, and human with sudden wind and rain. REFERENCES Bihonegn, T., & Bekele, F. (2018). Colic in Equine: A Review Article. 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YC Freeman, D. (2021). Effect of Feed Intake on Water Consumption in Horses: Relevance to Maintenance Fluid Therapy. Frontiers in Veterinary Science, 8: 1-7. ER Guthrie, A.J., & Lund, R.J. (1998). Thermoregulation. Base mechanisms and hyperthermia. Veterinary Clinics of North America: Equine Practice, 14: 45-59. % Harper, F. (2004). Winter Horse Feeding. Extension Horse Specialist Department of Animal Science, 23(1). 00 Hervik, A.K, & Svihus, B. (2019). The Role of Fibre in Energy Balance. Journal of Nutrition and Metabolism, Volume 2019: Article ID 4983657. 1 Hetem, R.S., Maloney, S.K., Fuller, A., Meyer, L.C.R., & Mitchell, D. (2007). Validation of a biotelemetric technique, using ambulatory miniature black globe thermometers, NO to quantify thermoregulatory behaviour in ungulates. Journal of Experimental Zoology, 307A: 342–356. D Hines, M. T. (2018). Clinical Approach to Commonly Encountered Problems. In: Reed, S.M., Bayly, W.M., & Sellon, D.C., (eds). Equine Internal Medicine, Elsevier: USA. ET Jørgensen, G., Aanensen, L., Mejdell, C., & Bøe, K. (2016). Preference for shelter and additional heat in horses exposed to Nordic winter conditions. Equine Veterinary NI Journal, 48(6): 720-726. RP Julliand, V., & Martin-Rosset, W. (2004). Nutrition of the performance horse. Wageningen Academic Publishers: Netherlands. Kristula, M., & McDonnell, S. (1994). Drinking water temperature affects consumption of water during cold weather in ponies. Applied Animal Behaviour Science, 41(3-4): 155-160. Langlois, B. (1994). Inter-breed variation in the horse with regard to cold adaptation: a review. Livestock Production Science, 40(1): 1-7. Legnani, S., Zini, E., Roccabianca, P., Funiciello, B., & Zanna, G. (2017). Dermoscopic analysis of the skin of healthy warmblood horses: a descriptive study of 34 cases in Italy. Veterinary Dermatology, 29(2): 165-169. Lindberg, J. E. (2013). Feedstuffs for horses. In: Geor, R.J., Harris, P.A., & Coenen, M., (Eds.). Equine Applied and Clinical Nutrition, Saunders Elsevier: China. Martin-Rosset, W., & Tisserand, J-L. (2015). Horse maintained outside - Critical Temperatures. In: Martin-Rosset, W (eds.). Equine nutrition: INRA nutrient requirements, recommended allowances, and feed tables, Wageningen Academic Publishers: Netherlands. McBride, G., Christopherson, R., & Sauer, W. (1985). Metabolic rate and plasma thyroid hormone concentrations of mature horses in response to changes in ambient temperature. Canadian Journal of Animal Science, 65(2): 375-382. McCutcheon, L., Geor, R., Ecker, G., & Lindinger, M. (1999). Equine sweating responses to submaximal exercise during 21 days of heat acclimation. Journal of Applied Physiology, 87(5): 1843-1851. Mejdell, C., & Bøe, K. (2005). Responses to climatic variables of horses housed outdoors under Nordic winter conditions. Canadian Journal of Animal Science, 85(3): 301- 308. Mejdell, C., Buvik, T., Jørgensen, G.,& Bøe, K. (2016). Horses can learn to use symbols to communicate their preferences. Applied Animal Behaviour Science, 184: 66-73. Mejdell, C., Jørgensen, G., Buvik, T., Torp, T., &Bøe, K. (2019). The effect of weather conditions on the preference in horses for wearing blankets. Applied Animal Behaviour Science, 212: 52-57. Merritt A.M., & Julliand V. (2013). Gastrointestinal physiology. In: Geor, R.J., Harris, P.A., & Coenen, M., (eds.). Equine Applied and Clinical Nutrition, Saunders Elsevier: China. Morgan, K. (1998). Thermoneutral zone and critical temperatures of horses. Journal of Thermal Biology, 23(1): 59-61. Santos, A., Rodrigues, M., Bessa, R., Ferreira, L., & Martin-Rosset, W. (2011). Understanding the equine cecum-colon ecosystem: current knowledge and future perspectives. Animal, 5(1): 48-56. 16 17Nutrient spotlight: Essential fatty acids Dr. Stephanie Wood, PhD Equine Nutrition, PgDip, BSc (Hons), RNutr (Animal), R.Anim.Tech Essential fatty acids have become a common topic when although in smaller quantities than long chain fatty acids (LCFA), with LCFA containing 16 and 18 carbons forming discussing equine nutrition, mainly due to our increased the majority of fatty acids. understanding of their integration into cells and tissues, and their important functions in physiological processes. To understand why these compounds are classed as essential in the diet we need to review their structure and function WHAT ARE ESSENTIAL FATTY ACIDS? We first need to understand lipids as a nutrient classification and the terminology used to describe them. Lipids is the term used to describe fats, waxes and oils, with each of these lipid types having their own properties, although all lipids are insoluble in water (McDonald et al., 2011). In plants, lipids form waxes that protect the plant’s structures, and oils which are mainly found in the seeds and nuts and that store energy. In animals, lipids are the main form of storing energy, mainly as adipose tissue (fat). Lipids also form animal cell membranes, hormones and are precursors for cells involved in immune responses Figure 1. Structure of fatty acids showing the terminal methyl end, also (McDonald et al., 2011). Fat is the term used for describing known as the omega end in the green dashed box, and the carboxyl end and carbon 1 in the red solid box. lipids that are solid at room temperature (22-23℃) whereas a) Palmitic acid which is a saturated long chain fatty acid containing 16 carbons and no double bonds (16:0). oils are liquid at this temperature, although often these b) Oleic acid containing 18 carbons and one double bond (highlighted terms are used interchangeably to describe the lipid content by arrow) making it an unsaturated LCFA. c) α-linolenic acid containing 18 carbons and three double bonds making of foods (Frankel, 2005). it an unsaturated PUFA. The green circle shows a methylene group that is found between carbons with double bonds. FATTY ACIDS Fatty acids are chains of carbon atoms linked to hydrogen Fatty acids are also described according to the number of atoms, with this chain attached to a carboxyl group at double bonds between carbons in their chain. Each carbon one end (Figure 1a). The carbon in the carboxyl group is has four binding sites for binding to hydrogen atoms and designated carbon 1 and the final carbon at the terminal end their neighbouring carbons. When all the carbons in the (methyl end) as the omega carbon (McDonald et al., 2011). chain are connected to each other via single bonds, and all The number of carbons in the chain influences whether the hydrogen sites are already bound, the fatty acids are said the fatty acid is referred to as a short chain (contains 1-6 to be saturated as there are no spare binding sites (Horton carbons), medium chain (contains 7-12 carbons), or long et al., 1996; McDonald et al., 2011). Saturated fatty acids chain (more than 12 carbons) fatty acid (Schönfeld & are straight in structure and so can pack tightly together, Wojtczak, 2016). Short chain fatty acids (SCFA) and meaning they can form more solid fat than those containing medium chain fatty acids (MCFA) are abundant in nature unsaturated fatty acids (Horton et al., 1996). 18 19Unsaturated fatty acids have one or more carbon 3), Omega-6 fatty acids those with the first double bond on atoms which have a double bond between them and their the sixth carbon (n-6), and Omega-9 fatty acids being those neighbouring carbon (Figure 1b). This means they still with the first double bond on the ninth carbon (n-9). For have space for additional hydrogen to join the chain, PUFA where there are multiple double bonds, the position making them unsaturated with hydrogens (Horton et al., of the other double bonds after that depicted by n- assumes 1996; McDonald et al., 2011). Unsaturated carbons have that there is one carbon that is linked to two other carbons bends in their chains at the site of the double bonds. These by single bonds (known as a methylene group) between bends mean the fatty acids cannot lie as tightly together as double bonds. This means there are three carbon atoms saturated fatty acids, resulting in them often being in liquid before the next double bond occurs (Figure 1c). form (Horton et al., 1996). ESSENTIAL FATTY ACIDS The number of double bonds leads to whether the fatty As previously stated, animals (and humans) are unable acid is referred to as a monounsaturated or polyunsaturated to produce fatty acids with double bonds closer than nine fatty acid (PUFA). Monounsaturated fatty acids have carbons to the omega end. This means that long chain a single double bond whereas PUFA have two or more Omega-3 and Omega-6 fatty acids cannot be produced as double bonds. Animal cells cannot add double bonds on the the double bond occurs before the ninth carbon (McDonald last nine carbons from the omega carbon (McDonald et al., R et al., 2011), meaning a dietary source of these fatty acids EP 2011), therefore fatty acids requiring double bonds closer should be fed. Nutritionally important fatty acids, their AP than nine carbons cannot be synthesised and so must be sources, number, and position of double bonds are shown DEL supplied in the diet. Such fatty acids are classed as essential in table 1. From table 1 it is evident that providing dietary CY fatty acids. C sources of essential fatty acids is relatively straight forward ER as they are present in feeds commonly fed to equids. Horses FATTY ACID NOMENCLATURE %00 consuming cereal grains will be consuming more of the Fatty acids are stated as the number of carbon atoms 1 N Omega-6 fatty acids than they would on a forage or pasture- followed by the number of double bonds. O D based diet. Of interest are the different proportions of fatty ET The fatty acid Palmitic acid is stated as 16:0 as it acids present in oils commonly fed to horses (Table 2). NIR contains 16 carbons and no double bonds, making it a When feeding oil, the primary focus may be on the amount P saturated LCFA. of calories that the oil can provide, meaning the fatty acid profile may be a secondary consideration, however the When fatty acids contain double bonds either the number influence fatty acids can have on physiological processes of double bonds or the position of the double bonds is mean the fatty acid profile of the oil fed may also need to provided. In the nutrition field, the number of double bonds be considered. is stated along with the position of the first double bond FUNCTIONS OF FATTY ACIDS from the omega carbon. For example, Oleic acid, the main Individual, free fatty acids only occur in trace amounts fatty acid in olive oil, is a monounsaturated fatty acid stated in living cells and mainly occur joined (esterified) to a as 18:1 n-9, meaning it contains 18 carbons and one double glycerol molecule to form glycerolipids (Frankel, 2005), bond which is positioned at the ninth carbon from the including triglycerides and phospholipids. Triglycerides are omega carbon (Figure 1c). This nomenclature leads to the formed by one glycerol molecule which has three carbons, popular terms Omega-3, Omega-6 and Omega-9 fatty acids joining with a fatty acid at each of these carbons (three fatty which are used in human and animal nutrition to group acids in total). Triglycerides are important storage lipids in PUFA by the position of the first double bonds from the animals and plants and are the main constituents of oils omega carbon. Omega-3 fatty acids are those with the first and fats, which contain mixtures of different triglycerides. double bond on the third carbon from the omega carbon (n- 18 19Table 1. Fatty acids commonly found in feeds fed to equids Position of Fatty acid Sources* Nomenclature No. double bonds double bonds** Saturated Cereal grains Palm oil 16:0 0 N/A Palmitic Soybean oil Cottonseed oil Unsaturated Omega-3 group Fresh/preserved forages α-linolenic Linseed oil 18:3 n-3 3 9, 12, 15 Rapeseed oil Microalgae Eicosapentaenoic Fish oils 20:5 n-3 5 5, 8, 11, 14, 17 (EPA) Green lipped mussels Docosahexaenoic Microalgae (DHA) Fish oils 22:6 n-3 6 4, 7, 10, 13, 16, 19 Green lipped mussels Omega-6 group Cereal grains Corn oil 18:2 n-6 2 9, 12 Linoleic Soybean oil Sunflower oil Arachidonic Microalgae 20:4 n-6 4 5, 8, 11, 14 Omega-9 group Cereal grains Oleic Olive oil 18:1 n-9 1 9 Rapeseed oil * Sourced from McDonald et al. (2011), Rosentrater & Evers (2018), Glasser et al. (2013), Maples (2013). ** Position of double bonds indicated by carbon number from the carboxyl end. Triglycerides containing predominantly saturated fatty cells and their compartments, allowing them to function acids are found in solid fats due to their ability to pack as separate entities with specific purposes (Goodman, tightly together, whereas triglycerides in oils predominantly 2020). Phospholipids are formed by one glycerol molecule contain unsaturated fatty acids, therefore oils are richer joining to two fatty acids and one phosphoric acid. The sources of essential Omega-3 and Omega-6 fatty acids fatty acids are insoluble in water making them hydrophobic than fats. (water hating) and are termed non-polar, whereas the phosphoric acid is hydrophilic (water loving) and termed Phospholipids are important structural lipids that form polar. The water loving and water hating properties of cell membranes in animal and plant cells. Cell membranes phospholipids enable them to form lipid bilayers which are vital to life and health as they form the boundaries of 20 21Table 2. Omega-3, -6 and -9 fatty acid content (g/100g of total fatty acids) of oils commonly fed to equids (adapted from NRC, 2007) Position of Fatty acid Sources* Nomenclature No. double bonds Fatty acids double bonds** Omega-3 Omega-6 Omega-9 Saturated Oil α-linolenic Eicosapentaenoic Docosahexaenoic Linoleic Oleic Cereal grains Rapeseed 11.1 - - 22.1 53.8 Palm oil 16:0 0 N/A Palmitic Soybean oil Corn 0.7 - - 58.0 24.2 Cottonseed oil Linseed 53.3 - - 12.7 20.2 Unsaturated Soybean 6.8 - - 51.0 22.8 Omega-3 group Sunflower 0.2 - - 39.8 45.3 Fresh/preserved forages Palm 0.2 - - 9.1 36.6 α-linolenic Linseed oil 18:3 n-3 3 9, 12, 15 - - Olive 0.6 7.9 72.5 Rapeseed oil 10 8.3 Fish oils* 1.3 1.8 12.0 Microalgae Eicosapentaenoic * Data adapted from Sargent (1997) Fish oils 20:5 n-3 5 5, 8, 11, 14, 17 (EPA) - Data not reported Green lipped mussels RE Docosahexaenoic Microalgae P The Omega-3 and -6 fatty acids are important in this comprise cell membranes (Figure 2). The fatty acid within AP (DHA) Fish oils 22:6 n-3 6 4, 7, 10, 13, 16, 19 inflammatory cycle, with the Omega-6 fatty acid the bilayers influences the fluidity of the cell membrane, DE Green lipped mussels L Linoleic acid, which is found most abundantly in cereal with phospholipids containing more unsaturated fatty acids C Omega-6 group Y grains, being involved in the pro-inflammatory processes, C having greater fluidity than those containing more saturated E Cereal grains R and the Omega-3 fatty acids found predominantly in fatty acids (Horton et al., 1996; Goodman, 2020). % Corn oil 0 pasture, forage, fish oils and algae, having key roles in 18:2 n-6 2 9, 12 Linoleic 01 Soybean oil INFLAMMATORY ROLE OF FATTY ACIDS resolving inflammation. N Sunflower oil Essential fatty acids have received considerable attention O D Arachidonic Microalgae 20:4 n-6 4 5, 8, 11, 14 E due to their role in inflammatory processes. Inflammation TN Omega-9 group I is the body’s normal defence mechanism against injury RP Cereal grains and infection and is required for the destruction and Oleic Olive oil 18:1 n-9 1 9 removal of pathogens and repair of affected tissues (Calder, Rapeseed oil 2010, 2015). We all know the heat, swelling, redness, pain and reduced movement that signify inflammation, and these symptoms reflect the increased blood supply and infiltration of inflammatory mediators at the site of Figure 2. Simplified illustration of a Phospholipid bilayer that makes up inflammation (James et al., 2000; Calder, 2010). These cell membranes. The water loving (hydrophilic) phosphoric acid heads make up the outer surfaces of the bilayer, whilst the insoluble, water responses are important and help to protect the body hating (hydrophobic) fatty acids sit inside the bilayer. however when inflammation continues over a prolonged period tissues can become damaged (Duvall & Levy, Upon digestion, both Omega-3 and Omega-6 fatty acids 2016). To avoid continued inflammation the body uses are metabolised to longer chain fatty acids containing negative feedback mechanisms to stop the inflammatory 20 and 22 carbon atoms. This process requires enzymes process. Anti-inflammatory mediators are secreted, pro- known as desaturases which add another double bond to the fatty acid chain, so making the chain less saturated inflammatory signals are inhibited, and regulatory cells and hence the name desaturases. Further enzymes known are activated (Calder, 2010). 20 21as elongases add two carbons to the fatty acid chains, injured site of dead and dying cells and reduce chemical and this is followed by a further desaturation stage. The signals that attract leukocytes to the injured site, reducing Omega-6 fatty acid Linoleic (18:2 n-6) is metabolised to the pro-inflammatory signals and resolving inflammation Arachidonic acid (20:4 n-6), whilst α-linolenic acid (18:3 (Duvall & Levy, 2016). n-3) is metabolised to Eicosapentaenoic acid (EPA) (20:5 n-3). Eicosapentaenoic acid can undergo further stages of elongation and desaturation to produce Docosahexaenoic acid (DHA) (22:6 n-3) (Simopoulos, 2016) (Figure 3). The desaturase enzymes have preference for the Omega-3 fatty acid α-linolenic acid however a high intake of Linoleic acid can interfere with desaturation of α-linolenic acid (Simopoulos, 2016). PRO-INFLAMMATORY PROCESSES Arachidonic acid is incorporated into phospholipids that comprise cell membranes, including the membranes of leukocytes (macrophages, neutrophils and lymphocytes). Upon injury or irritation, Arachidonic acid is released from cell membranes and is enzymatically converted to eicosanoids which are inflammatory mediators and include prostaglandins, thromboxanes and leukotrienes (Calder, Figure 3. Structure of the Omega-3 fatty acid α-linolenic acid (18:3 n-3) which is enzymatically converted to Eicosapentaenoic acid (EPA) (20:5 2010). In addition, leukocytes (white blood cells) travel to n-3) and Docosahexaenoic acid (DHA) (22:6 n-3). the injured site to defend the body against pathogens. The infiltration of blood and leukocytes combined with the release and conversion of Arachidonic acid from It is evident that both pro-inflammatory and anti- cell membranes, results in the swelling we associate inflammatory processes are essential for maintaining a with inflammation. healthy immune response and protecting the body against disease. Prolonged inflammation however, damages cells INFLAMMATORY RESOLVING PROCESSES and is debilitating for the animal. Both Omega-3 and -6 In contrast to Arachidonic acid, the Omega-3 fatty acids are important in the diet although studies in humans and EPA and DHA have anti-inflammatory properties due to their animals have shown that the inflammatory response conversion to pro-resolving mediators. Eicosapentaenoic can be partly manipulated through the ratio of Omega-3 acid and DHA are found in the blood plasma and in cell to Omega-6 fatty acids in the diet (James et al., 2000), membranes (Duvall & Levy, 2016). When inflammation resulting in beneficial effects on the management of develops EPA and DHA flow to the site via the plasma certain conditions. where they are enzymatically converted to the pro-resolving mediators resolvins, protectins and maresins (Duvall & DIETARY SOURCES OF FATTY ACIDS Levy, 2016). Specifically, EPA is converted to E-series As shown in tables 1 and 2, cereal grains, corn oil resolvins and DHA to D-series resolvins, protectins and and soya bean oil supply predominantly Linoleic acid maresins. Eicosapentaenoic acid and DHA present in cell (n-6), whilst pasture, forages, linseed oil and rapeseed membranes can also be released and converted, increasing oil predominantly supply α-linolenic acid (n-3). What is the levels of pro-resolving mediators. These pro-resolving also evident is that plant-based foods are poor sources of mediators are part of a cascade of processes that clear the Arachidonic acid, EPA and DHA used by the body in the 22 23to horses, therefore the choice of which to feed is dependent inflammatory cycle, meaning the body must convert Linoleic on owner preference. and α-linolenic acid to these longer chain fatty acids. Conversion of α-linolenic acid in particular is extremely HEALTH BENEFITS OF OMEGA-3 FATTY ACIDS inefficient in mammals (including humans) (Gibson et al., There are multiple health benefits reported in humans 2013; Ross-Jones et al., 2014; Calder, 2015), therefore attributed to consuming a diet containing more Omega-3 the amount of EPA and DHA produced from consuming fatty acids compared to Omega-6 fatty acids. Research in and metabolising plant sources of α-linolenic acid is low. animals also shows health benefits although studies have For many horses this low dietary intake may be sufficient, mainly focused on the common health issues affecting making linseed and rapeseed products ideal for feeding domestic species. Specific to horses, research has focused alongside a pasture/forage-based diet. Horses performing on the effects of feeding fatty acids on joint, respiratory, and skin health, and on their benefits for breeding stock. more demanding exercise, breeding stock or those suffering from inflammatory related conditions however may benefit JOINT SUPPORT from consuming a dietary supply of EPA and/or DHA to Research in humans and dogs has shown that a dietary help support the inflammatory-resolving processes (Ross- supply of Omega-3 fatty acids is associated with a reduction Jones et al., 2014; Nogradi et al., 2015; Duvall & Levy, in inflammation and/or pain associated with osteoarthritis R 2016). Traditionally the only way of providing a dietary (Gruenwald et al., 2009; Fritsch et al., 2010), supporting EP source of these fatty acids was in the form of Cod Liver A the view that these fatty acids may be beneficial to horses. P Oil products as these contained notable amounts of EPA D Woodward et al. (2007) compared the stride length, EL and DHA (Sargent, 1997). Fish oils continue to be popular CYC for supplying EPA and DHA in equine diets, however they ER are not that palatable to horses (McMillan et al., 2012; %00 Jerina et al., 2021), therefore Green Lipped Mussels (Perna 1 N canaliculus) have been used over recent years to supply O D EPA and DHA. ETNI The high levels of EPA and DHA in fish oils and RP Figure 4. Oils containing microalgae now offer a vegan alternative to Green Lipped Mussels are due to these animals feeding on marine sources of EPA and DHA. microalgae within the water they live (Miller et al., 2014). These microalgae contain high concentrations of Omega-3 lameness score, plasma fatty acid concentrations, and fatty acids which are then found in animals that consume inflammatory marker levels of horses fed EPA and DHA for them, with the amount of EPA and DHA within the algae 75 days, with those of horses fed a control diet of corn oil specific to the microalgae species and environment in (high in Omega-6). Trot stride length measurements taken which it grows (Adarme-Vega et al., 2012). There is now on day 75 had increased by 6.6% (~15cm) in horses fed great interest in the opportunities that microalgae provide EPA and DHA compared to their measurements at the start as dietary sources of Omega-3 fatty acids as they are more of the study, whereas there were no changes in stride length sustainable sources than fish oils (Figure 4). When we of horses receiving the control diet. The EPA and DHA consider options for feeding to horses, algae align more treatment also resulted in an increase in n-3:n-6 ratio and to the natural vegan diet of equids as algae are classed as plasma DHA concentration throughout the study but had no thallophytes which are plants lacking in roots, stems and effect on EPA levels. The authors also reported an increase leaves (Lee, 2008). Green Lipped Mussels and fish oils in Arachidonic acid concentrations in both the control and continue to be popular and suitable ingredients for feeding EPA/DHA treatment groups, which was an unexpected 22 23result and attributed to the corn oil in the control diet and The trend for lower PGE2 concentrations in synovial fluid following supplementation with EPA and DHA align with higher than expected Linoleic and Arachidonic acid levels previous results by Manhart et al. (2009) who also reported in the EPA/DHA supplement. Inflammatory markers were lower inflammatory markers in the synovial fluid of horses not affected by the feeding of EPA and DHA in this study, fed EPA and DHA. although this may be due to the presence of Omega-6 fatty acids in the treatment diet which have a pro-inflammatory Positive results for the feeding of dried Green Lipped action. Exercise sessions in the study also varied between Mussel extract on lameness in horses were reported by horses and treatments, as the horses were used for student Cayzer et al. (2012). In a randomised, double-blind, riding sessions. As such, some horses may have performed placebo-controlled study, the effect of feeding Green Lipped more demanding exercise than others, potentially Mussel extract to horses for 53-59 days on lameness scores, influencing inflammatory marker levels. flexion tests and joint pain were compared to the same measurements from horses receiving a cellulose based Ross et al. (2010) studied the effect of feeding flaxseed placebo. None of the lameness scores of the 19 horses in (linseed) and fish oil for 90 days on the presence of EPA the Green Lipped Mussel group worsened over the study and DHA in equine synovial fluid. Synovial fluid extracted period, with seven horses’ scores remaining the same from the carpal (knee) joints of horses consuming the fish whilst 12 horses’ scores improved. In comparison, six of oil contained EPA and DHA, whereas these fatty acids the horses in the placebo group recorded a worse lameness were undetectable in synovial fluid from horses consuming score, whilst 11 remained the same and three showed flaxseed and those in the control group (no supplement). improvements. The improvements in lameness score seen A very similar study was also performed by Ross-Jones et in the supplemented horses were also greater compared to al. (2014) comparing the feeding of flaxseed with a marine the placebo group. Greater improvements in flexion tests supplement (fish oil and algae combined) for 90 days, were also seen in the supplemented horses compared to although the authors measured fatty acid concentration improvements in the control group. Pain measurements in plasma and synovial fluid, and inflammatory marker were also significantly reduced in the supplemented group. (prostaglandin E2 [PGE2]) levels in synovial fluid. As These results indicate that a Green Lipped Mussel extract would be expected, feeding flaxseed increased plasma may be of benefit to horses to support joint function and concentrations of α-linolenic acid, however it also increased relieve discomfort due to osteoarthritis, with these results concentrations of Linoleic acid. The marine supplement potentially related to the high EPA and DHA content increased levels of plasma Arachidonic acid, EPA and DHA of the mussels. compared to the control and flaxseed groups, with EPA and DHA only being detectable in horses receiving the marine Studies on the effects of microalgae in horses are limited supplement. The marine supplement also increased levels due to algae being a relatively new ingredient in the equine of EPA and DHA in synovial fluid, whereas these fatty and animal supplements market. Brennan et al. (2017) acids were either undetectable or present in extremely low compared lameness scores, heart rate and blood cytokine levels in the synovial fluid of horses consuming flaxseed levels (cell signalling molecules) of horses following 60 and the control diets. Synovial PGE2 concentrations did not days of either a microalgae supplement high in DHA (DHA differ statistically between treatment groups, however there level not provided), or a placebo diet. Following the 60 was a trend for PGE2 concentration to be lower in horses days of treatment/placebo baseline measurements were consuming the marine supplement compared to horses in taken for each horse, after which acute joint inflammation was simulated through injection of lipopolysaccharide the other two groups. The studies by Ross et al. (2010) and into a single knee joint on each horse. All measurements Ross-Jones et al. (2014) support the view that α-linolenic were repeated 12, 24 and 48 hours after joint injection. acid is not effectively converted to EPA or DHA in equids. 24 25alongside samples of blood and bronchoalveolar lavage Horses who had consumed the microalgae supplement fluid (BALF) taken from the respiratory tract (Nogradi had lower heart rates and lameness scores 12 hours after et al., 2015). Horses were assessed before receiving the joint injection compared to the placebo group, although supplement/placebo and then again 56 days (8 weeks) later. there were no differences between groups at 24 and 48 During the 8-week study period horses were fed a pelleted hours for these measurements. Cytokine levels (signalling diet and not permitted any forage (hay). Respiratory scores molecules interleukin-1β and interleukin-8 which have pro- were significantly improved for all horses, regardless of inflammatory roles) were raised in the placebo group but whether they received the EPA/DHA or placebo treatment, not in the microalgae supplemented group 12 hours after although the improvements were greater in the EPA/DHA injection, but not at 24 and 48 hours. Lipopolysaccharide treated horses. The improvement in all horses regardless of injections are used to stimulate inflammation in joints as group is likely due to reduced exposure to dust and irritants a model for acute synovial inflammation due to its short- present in hay, although improvements were seen quicker acting effect, which explains the reduction in cytokine in horses receiving the EPA/DHA treatment indicating they levels and lameness scores 24 and 48 hours after injection were not solely due to hay being removed from the diet. in all horses. The absence of any worsening in lameness, A 10-fold increase in plasma DHA concentration and a or increase in cytokines, 12 hours post injection in horses decrease in neutrophil percentage in BALF collected from who had consumed the microalgae supplement, indicate RE horses receiving the EPA/DHA supplement, support this P that microalgae is a suitable source of dietary DHA that AP view and indicate that feeding EPA and/or DHA can help could support joint function through modification of pro- DE to manage respiratory conditions caused by inflammation. L inflammatory signalling molecules. CYC Results from a recent study by Christmann et al. (2021) RESPIRATORY SUPPORT ER offer further support for feeding EPA and/or DHA to horses Inflammation in the horse’s lower airway is associated %00 with inflammatory lower airway conditions, as they found with an increase in leukocytes (white blood cells: 1 N increased DHA and EPA concentrations in plasma and neutrophils, eosinophils, mast cells) and an excessive O BALF collected from horses receiving a fish-based dietary D accumulation of mucus in the airways (Couëtil et al., 2016). ET supply of these fatty acids, compared to samples from Clinical signs such as coughing, nasal discharge, increased NIR horses receiving no supplement (control group). Horses P respiratory rate at rest and/or during exercises, and reduced received the diets (EPA/DHA or control) for 90 days and performance are displayed to varying degrees in affected results showed it took until day 60 of the study for the horses. Exposure to non-infectious agents such as fungi, increases in EPA/DHA to be seen, indicating that long- moulds, endotoxins, mites, debris, and ultrafine particles term supplementation of horses with EPA and/or DHA is are the principle causes, and any reduction in inflammation required for their integration into body fluids, and influence and associated clinical signs requires reduction of exposure on inflammatory processes, to be seen. through management of the horse’s environment. In addition to managing the horse’s environment the feeding SKIN SUPPORT of Omega-3 fatty acids may reduce the inflammatory Linseed oil and micronised linseed meal are ingredients response through a reduction in pro-inflammatory signals included in horses’ diets due to their low starch and sugar, and production of pro-resolving mediators as previously and high protein and fat content (NRC, 2007). These described. Horses diagnosed with inflammatory airway nutritional qualities lead to linseed products being fed as disease (IAD) and recurrent airway obstruction (RAO) a source of low-starch energy and to support skin and hoof health. The fatty acid profile of linseed meal/oil is high were fed either a dietary supply of EPA and DHA from in Omega-3 α-linolenic acid and low in Omega-6, which microalgae as part of a respiratory supplement, or a make it particularly helpful for inflammatory issues such placebo, and assessed for their respiratory function 24 25as Culicoids hypersensitivity, commonly known as sweet or DHA would also be beneficial to determine if a dietary source of these fatty acids would be helpful in managing itch. The majority of research into the benefits of feeding skin issues in horses. Omega-3 fatty acids for skin issues has been performed in humans (Sawada et al., 2021) and dogs and cats (Magalhaes BREEDING SUPPORT et al., 2021) with few studies performed in horses. Results Docosahexaenoic acid is of particular interest for were favourable in most studies, particularly for skin breeding stallions as spermatozoa contain high levels conditions associated with inflammation. Friberg (1999) of PUFA, particularly DHA (Brinkso et al., 2005). As compared the effect of feeding 200ml linseed oil or 200ml DHA must be supplied within the diet, what the stallion corn oil to horses with sweet itch in a double-blind study is fed directly influences the fatty acid composition of the so neither the owners nor those assessing the horses' skin sperm plasma membrane (Brinkso et al., 2005). Studies lesions knew which oil was fed to which horse at any time in boars have shown that a high DHA to Omega-6 ratio point in the study. All horses consumed both diets in a cross- enhances fertility, whilst a low ratio reduces fertility. The over design, consuming each individual oil for 6 weeks, semen of stallions used for artificial insemination (AI) can with a 6-week period between each oil being fed. Results be affected by the cooling and storage process leading to were based on the number of skin lesions and total skin what is known as cold shock. Cooling of sperm can disrupt lesion area. Oil type made no statistic difference in skin the sperm membrane lipids and damage the mitochondria lesion numbers or total lesion area, although owners stated (energy centre) within the sperm leading to loss of sperm that their horse’s skin improved when fed the linseed oil. motility (ability of sperm to move), viability (number of In contrast, O’Neill et al. (2002) found that after 42 days live sperm) and fertilisation capability (Parks & Graham, of supplementation, the area of skin affected by sweet itch 1992). Brinsko et al. (2005) studied the effect of feeding a was significantly less in horses fed linseed meal compared fish oil supplement high in DHA on stallion sperm motion to those fed a placebo of bran. The same study took skin qualities. Horses received either the fish oil supplement biopsies from the horses to determine fatty acid profiles or a control diet (no supplement) for 14 weeks, followed but found the addition of linseed meal made no change to by 14 weeks with no supplement, after which time horses fatty acid profiles. The lack of change in skin fatty acids, swapped treatments for a further 14 weeks. Baseline semen but decrease in skin reaction, indicates that the potential samples were taken before treatments and then after each beneficial effects of feeding linseed may be related to 14-week period and analysed for quality and fatty acid other beneficial properties aside from α-linolenic acid, for content. Samples were assessed as fresh samples, cooled example amino acids, or that the low conversion rate of samples which had been stored for 24 hours, cooled α-linolenic acid to EPA and DHA is still enough to support samples stored for 48 hours, and frozen then thawed skin health, but not enough to cause a detectable increase samples. Feeding a dietary source of DHA to the stallions in the levels of these fatty acids in the skin. The use of resulted in a considerable increase in sperm concentration linseed meal which contains amino acids and not just fatty within ejaculates and the level of DHA within sperm and acids, would also explain the difference in results found semen. Motion characteristics of fresh sperm were not between the Friberg et al. (1999) and O’Neill et al. (2002) affected by feeding DHA, however sperm moved at a faster studies, although further research is needed to understand speed and in a straighter direction in samples that had been the benefits of different linseed products to horses with cooled and stored for 24 hours and taken from horses fed skin issues. Research into the effects of feeding EPA and/ the DHA supplement. In samples cooled and stored for 48 26 27hours, sperm from horses fed DHA also had greater total a similar conclusion to that of Brinsko et al. (2005), that and partial motility which are assessments for the number feeding of a dietary source of DHA could be beneficial of sperm moving forwards in a straight line. Positive for stallions with lower fertility and whose sperm do not results for feeding DHA were also seen in samples that tolerate cold shock. were frozen then thawed, a process known to reduce sperm SUMMARY motility. The reduction in motility due to freezing/thawing The feeding of fat to horses provides a concentrated was less in the DHA supplemented horses than those on form of energy and is able to influence the essential fatty the control diet. The authors concluded that feeding a profile within the body. Due to their vital roles within the dietary source of DHA could be particularly beneficial body, both Omega-3 and -6 fatty acids are essential within for stallions with lower fertility and who produce sperm the diet, with concentrates and associated oils being high that do not tolerate cooling and freezing processes. These in Omega-6, and forage, linseed and marine derived oils results are supported by a more recent study by Garmsir being high in Omega-3. Feeding a diet with a higher et al. (2014) who compared the effects of feeding fish oil, Omega-3 to Omega-6 ratio influences the inflammatory fish oil combined with Thyme, just Thyme, and a control processes, with Omega-3 fatty acids EPA and DHA shown diet (no supplementation) on semen and sperm samples RE to have inflammatory-resolving actions. Such actions collected from Caspian stallions. This study also found that PAP make them useful additions to the diets of horses affected after 60 days, sperm concentration and ejaculate volume DE by joint, respiratory, and skin inflammation. In addition, L increased with fish oil supplementation (with and without CY dietary sources of DHA could benefit stallions with Thyme). Similarly, motility of fresh sperm was unaffected CER reduced fertility or cold shock sensitive sperm. Options for by supplementation however motility, membrane integrity %0 supplying EPA and DHA include fish oils, Green Lipped 0 and membrane viability of cooled and stored sperm (24 1 N Mussels and microalgae, with the latter offering a vegan and 48 hours) was increased after receiving the fish-oil- O D source which aligns most closely to the natural equine diet. based supplements for 60 days. Garmsir et al. (2014) drew ETNIRP 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. 26 27REFERENCES Adarme-Vega, T.C., Lim, D.K.Y., Timmins, M., Vernen, F., Li, Y., & Schenk, P.M. (2012). Microalgal biofactories: a promising approach towards sustainable omega-3 fatty acid production. Microbial Cell Factories, 11: 96. Brennan, K.M., Whorf, C., Harris, L.E., & Adam, E. (2017). 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Equine and Comparative Exercise Physiology, 4(2): 71-78. 28 29Maintaining skin health during wet, cold weather Orsolya Losonci BSc (Hons), EEBW, Member of the IAABC and IEBWA MUD FEVER AND RAIN SCALD Rain scald on the other hand, typically presents in Humid, rainy weather, slippery and muddy gateways – a the form of paintbrush-like scabs on the back and the nightmare for all involved. As winter months sneak in so hindquarters of horses (Figure 2). Other clinical signs may do common equine skin conditions, with conditions such as include patches of hair loss and dusty-looking hair (Hamid, rain scald and mud fever being prevalent. The causes and 2016; Frye et al., 2019). treatments for these two conditions are similar, however, their clinical signs and location of these signs differ. In the acute stage of mud fever, clinical signs typically appear in the form of cracks and lesions at the caudal (back) aspect of the pasterns with fresh pus leaking out of them. REP Some swelling, redness, irritation, hair loss and crusts may AP also be present at this stage. In chronic cases, all of the DEL above along with hardened crusts (Figure 1) are commonly CY present (Hamid, 2016; VeterianKey, 2016; Marsella, 2019; CER SevernEdge, 2021). Lameness and pain on palpation are Figure 2. Characteristic paintbrush like scabs on the horse’s back % (Source: Author). 0 typical in these advanced cases and horses may object 01 to treatment. If left untreated, old crusts may stimulate NO The causative bacterial agents of both conditions DE include Dermatophilus congolensis, Staphylococcus spp., TNI and Pseudomonas aeruginosa as well as fungi such as RP Dermatophytes. All of which may be present in the horse’s environment in the form of hyphae (Scott & Miller, 2011) but are harmless in the dormant stage. Even concentrated amounts of these bacteria will not be able to cause infection to an intact skin (Scott & Miller, 2011), which is why some horses may live in wet, muddy conditions for a prolonged period of time without developing these conditions. Certain types of soil and old crusts may act as a temporary Figure 1. Mud fever at the caudal aspect of the pastern. reservoir for Dermatophilus c. (Scott & Miller, 2011; Aufox et al., 2018; Marsella, 2019) where the bacteria remain dormant until environmental conditions become ideal for development of further cracks and other skin trauma, reactivation (VeterianKey, 2016). Bacteria tend to thrive eventually leading to heavy scab formation (Hamid, 2016). in a wet, warm environment, such as the caudal aspect of Mud fever can be a debilitating condition for horses in work the pastern. They enter the epidermis (outer layer of the and those actively competing. Working in sandy schools or skin) (Figure 3) at the site of an injury which could be an wearing boots may not be appropriate until clinical signs open wound or an insect bite, and trigger an inflammatory have resolved. 28 29Usually, both skin conditions develop from the late response, causing scabs or crust formation at the site of autumn until early spring months, with the first lesions trauma (VeterianKey, 2016; Aufox et al., 2018; Marsella, tending to occur 2–3 weeks after the onset of the rainy 2019; SevernEdge, 2021). Transmission of the causative season. The likelihood of actual onset is heavily dependent agents is possible via biting insects and potentially also on management practices (Marsella, 2019) (Table 1). via direct contact with acute lesions (Underwood et al., 2015). The incubation period is extremely variable, lasting MANAGEMENT CONSIDERATIONS anywhere between one and 34 days (Scott & Miller, 2011). Prevention is always better than cure and is less stressful for all involved, with good management practices being of primary importance. Flexibility to adjust routines and COMMON PREDISPOSING FACTORS INCLUDE, BUT ARE NOT LIMITED TO: • Prolonged wetting of the skin (Marsella, 2019) • Over-rugging causes horses to sweat under the rug (Scott & Miller, 2011) • Lack of, or ineffective grooming Figure 3. Layers of the skin that form a protective barrier between the • Maceration of skin (Hamid, 2016) horse and its environment. • Microtrauma to the skin via brushes with stiff PREDISPOSING FACTORS bristles (Scott & Miller, 2011; Hamid, 2016) In wet and muddy conditions, the equine skin may • Mineral deficiency (Hamid, 2016) remain damp for a prolonged period. Moisture causes the • Overreach injury release of infective zoospores of bacteria or fungi into the • Open wound or cut outermost layer of the skin, the epidermis (Cullinane et al., • Sunburn or allergies causing itchiness and hence 2006; Marsella, 2019). At the same time, protective bacteria self-trauma on the skin such as Bacillus spp. and Staphylococcus spp. are diluted due to prolonged exposure to heat and humidity • Skin trauma caused by working on sandy ground (Hamid, 2016; Frye et al., 2019). Damage to the oily • Excessive washing of the legs layer of the skin may also happen (Ashton, 2020), and • Leg mites or other insect bites imbalances in these epidermal constituents may play a • Attachments of ticks causing inflammation role in the development of infection, although thickness of (Nicholson et al., 2019) the skin was not found to be a contributing factor (Scott • Suppressed immune system & Miller, 2011). According to Scott & Miller (2011) the intensity of rainfall may be more important than the total • Poor nutrition amount of rain, suggesting that a sudden insult to the skin • Poor body condition also increases the risk of these conditions. • Rubbing boots, bandages, saddle cloths and tack The immune response of the horse is critical in • Wet-dry cycle causing dry skin and skin cracks determining an individual animal’s resistance to infection • Standing in dirty bedding (Marsella, 2019). Horses with a weakened immune system • Poor hygiene such as those with Pituitary Pars Intermedia Dysfunction (PPID – commonly referred to as Cushings) may require • Parasitic infection nutritional support to aid resistance against bacterial • Lymphoma (Scott & Miller, 2011; Marsella, 2019) skin conditions. 30 31implement changes to the horse’s management are essential While daily turnout is crucial for equine welfare, limiting the skin's exposure to mud and moisture may be a greater, for prevention during wet weather and successful treatment short-term concern, particularly for severe cases. Options should the conditions develop. include individual stabling or hard standing areas that still Feral (free-living) and domestic horses alike naturally allow free movement and time outside with other horses. seek to avoid muddy areas. However, in domestic situations If stabled, the stable and the horse’s legs should be kept this is often not possible due to restricted amounts of space clean and dry at all times. Picking up droppings several and motivating factors to stay in busy areas such as the times during the day and daily removal of soiled bedding is gate, the hay pile or the shelter. This motivation may be the most appropriate course of action for mud fever cases. greater than the urge to move away to a drier area, leading To help keep your horse relaxed when stabled seek out to horses being exposed to mud and rain for prolonged enrichment options, stable toys and activities you can do to periods of time, and an increased risk of mud fever and keep them occupied, along with providing enough forage to rain scald developing. However, we all know that mud is allow trickle feeding behaviour. an unavoidable part of owning and working with horses. A Bedding may also play a primary role in managing this small amount of mud may even be beneficial to the horse’s condition. According to Yarnell et al., (2017) pine bedding skin, helping to keep parasites away and stimulating the (shavings) (Figure 4) has been shown to discourage or slow sebaceous gland to produce natural oils that act as a barrier RE down bacterial growth of equine disease-causing bacteria against dust, water and bacteria (SevernEdge, 2021) and PA including Dermatophilus c., one of the bacteria responsible P which are beneficial for optimal hoof function. Exposure to D for mud fever and rain scald. Compared to other alternatives, E too much deep mud, however, can be detrimental to your LC such as straw, pine shavings showed the largest moisture- horse’s health. YC holding capacity of all bedding types tested, making it an ER HOW MUCH MUD IS TOO MUCH? appropriate choice for mud fever cases where moisture is to %0 Generally speaking, if the mud covers the hooves and 0 be avoided at all times. 1 reaches the coronary band it is considered to be suboptimal. NO This level of mud can increase the chances of mud fever, DE loosing shoes and soft tissue injuries, just to name a few. TNI Ideally the gate should be at the highest point of your field RP to avoid the build-up of mud, although such a busy area may still become muddy. To limit exposure to mud, the following options should be considered: • Move the horse to another field. • Rotate fields to avoid overuse. Figure 4. A clean stable helps to manage and reduce the likelihood of • Block off muddy areas with electric fence. mud fever. • Put down mats or wood chip as an alternative footing. According to Kim & Shin (2005) and Zeng et al. (2012) • Moving gates, hay and other commonly used areas. foot and respiratory health of horses improved when horses • Stabling the horse overnight or alternatively, were stabled on pine-based products. The antimicrobial keeping the horse in. properties of pine could be associated with stilbenes, a • Placing the hay in several piles encourages horses polyphenol found in the wood of pinus species (Välimaa to move around instead of eating in one place. This et al., 2007), especially corsican pine (pinus nigra). Choice also mimics natural browsing behaviour and correct of bedding could therefore be an important factor in the head and neck position - always make sure there are appropriate management of the condition. more hay piles than horses present in the field to avoid frustration and conflict amongst the herd. If your horse is kept at a yard where you cannot influence 30 31their management, there are still a few things you could do for over 3.5 years, even when heated and dried at 100°C, and for 13 years when frozen (Pilsworth & Knottenbelt, to help prevent mud fever and rain scald developing: 2007; Scott & Miller, 2011). Favourable conditions for its USE TURNOUT BOOTS growth include certain types of soil and moisture content, Turnout boots are developed to keep the legs clean and although the pH of the soil was found to not affect its dry while your horse is in the field. Look for those that survival (Scott & Miller, 2011). Such findings demonstrate provide all-round protection, made from a water-repellent the challenge of controlling such bacteria and treating these yet breathable material. Also, ensure that they are correctly common skin conditions. fitted to avoid slipping or rubbing of the skin. Ideally, you As rain scald and mud fever are multifactorial conditions, would have two sets so that you can clean and dry them for the same treatment plan may not be appropriate for each the next morning. horse. First and foremost, a proper diagnosis is essential CLIPPING LONG FEATHERS as rain scald may be mistaken for ringworm, a highly Clipping allows easy monitoring of the affected area, contagious fungal infection, and mud fever can be confused facilitates treatment, and allows more air to the lesions. with pastern and cannon leukocytoclastic vasculitis - an allergic reaction to sunlight and other environmental factors Avoid clipping your horse’s feathers without a valid (SevernEdge, 2021). reason. Horses’ coats are designed to guide water droplets to the ground without them coming in contact with the skin. Underlying conditions such as fungal or mite infections, Clipping off feathers could disrupt this natural mechanism allergies, or a suppressed immune system, can also influence and could in fact increase the risk of mud fever. treatment options (SevernEdge, 2021). Vets recommend treatment plans on a case-by-case basis after evaluating the AVOID FREQUENT WASHING OF LEGS severity of the individual case and any underlying primary Washing the legs on a daily basis removes the protective causes. Treatment depends on how advanced the case is and oils in the skin and may increase susceptibility to mud fever typically involves topical or systemic antibiotics (Hamid, (SevernEdge, 2021). If you do need to wash your horse’s legs, ensure that they are dried thoroughly with clean towels after washing, and particularly before exercise or turning the horse back out. A warm and moist environment will encourage the bacteria to grow. Sometimes a better way to keep the lower leg clean is to provide a thick bed in the horse’s stable to absorb the moisture, wait for the mud to dry overnight, and remove the dry mud the next day. Use a gentle brush with soft bristles Figure 5. Horses with an underdeveloped topline can be prone to rain to avoid causing microtrauma to the skin. This is also scald (Source: Author). the perfect time to check for signs of mud fever, such as 2016), anti-inflammatories and analgesics. Prognosis is new crusts. usually very good for average cases where the condition TREATMENT resolves in just a few weeks. However, treatment may be Once present, bacteria are difficult to eliminate. They prolonged for horses with a weakened immune system were the first organism on Earth and their adaptive nature (Marsella, 2019). enabled them to still be present today. They can even Make sure to notify your vet if the condition does not adapt to antibiotic treatment and produce up to 16 million improve or becomes worse. Documentation of skin lesions offspring per day (McDowell & Rowling, 2003). via regular photographs could be an objective way of Research on Dermatophilus c., one of the bacteria tracking the healing process. Removal and proper disposal responsible for rain scald and mud fever, found that it can of crusts may be advised for preventing reinfection (VeterianKey, 2016), although you should discuss with remain dormant in old crusts at temperatures of 28-31°C 32 33When antifungal and antibacterial scrub is SUMMARY OF PREVENTATIVE MEASURES recommended, apply it gently to avoid microtrauma to the skin. It is generally applied on a three- to four-day basis to • Make sure to check on current and new scabs/ prevent dry skin. After application, rinse and dry the skin crusts daily thoroughly. Application of an antibacterial barrier cream • Check horses with long feathers even more may also be recommended before turnout, however, always thoroughly (Knottenbelt, 2012). Long feathers make sure that the area is dry before applying and avoid may hide crusts and encourage the inflammatory product buildup. process by maintaining a warm and moist environment for the bacteria Horses that object to treatment procedures could benefit from the use of a lick or chaff as a distraction, or • Groom horses that are not in work with a curry comb on a daily basis. Horses with an operant conditioning. Ultimately, restraint or sedation may underdeveloped topline may be more prone to be necessary. rain scald due to pocket-like areas on the back and HERBAL REMEDIES hindquarters which trap in rain and dust (Figure 5) Herbal remedies may be used as complementary • Minimise exposure to rain and mud treatment options. Anti-inflammatory herbs cleanse the area • Limit chances of skin trauma to aid the inflammatory process rather than suppressing it. R Such herbs could be particularly helpful in inflammatory • Control external parasites (Underwood et al., 2015) EP skin conditions (Self, 2005) (Table 3). AP • Provide shelter for horses in the field or a rug as D Colloidal silver may also help in acute or chronic infected an alternative ELC wound management as it is known for its antibacterial, Y • Avoid over-rugging C antiviral and antifungal effects (McDowell & Rowling, ER 2003; Dharmshaktu et al., 2016). However, according to % your vet if the removal of crusts is appropriate in your 00 Schwarcz, (2019) colloidal silver may cause argyria, a 1 horse’s case, and the most appropriate method to perform condition where silver particles deposit in the skin, causing N such removal to avoid damaging the skin further. Scab O it to turn grey, making this a consideration for dark coloured D removal in rain scald cases may also be required. Pick ET horses or those with a showing career. Natural herbal paintbrush-like scabs with your fingertips but avoid picking NI creams may also be applied where appropriate. Look for R out those that do not come off easily. Leave them for a P ones with lavender, which acts as a natural insect repellent. few days until they are ready to be removed. Regardless The dosage of herbal remedies as well as possible of treatment method, wearing disposable gloves when adverse health effects are not always clear. For appropriate administering treatment is advised as the condition may application and dosage, consult with your vet and a qualified spread to humans, with immunosuppressed individuals being more at risk (Marsella, 2019). equine herbalist or nutritionist. Table 3. Herbal remedies and their effects. Herbal element Beneficial effects Natural antioxidant, speeds up wound healing processes Pycnogenol found in bark (McDowell & Rowling, 2003) Allicin in garlic Antibiotic effects (Varró, 2006) Shown to be clinically effective in the treatment of equine streptothricosis Tea tree oil (Frye et al., 2019) Herbs rich in sulphur Strengthen the coat and skin Used as an external antiseptic, helpful in reducing Apple cider vinegar irritation in sweet itch cases (McDowell & Rowling, 2003). 32 33NUTRITIONAL CONSIDERATIONS anti-inflammatory properties (Geor et al., 2013), with a correct ratio of Omega-3:Omega-6 fatty acids being highly A healthy skin protects the body from harmful beneficial for skin conditions, especially in acute or chronic environmental factors such as weather changes and injury. inflammatory cases (Geor et al., 2013). For an in-depth A balanced diet with optimum levels of Zinc, Copper explanation of Omega-3 and -6 fatty acids, including how they support the skin, please refer to Essential fatty acids by Dr. Stephanie Wood. SUMMARY In conclusion, mud fever and rain scald are both multifactorial equine skin conditions. Prolonged exposure Figure 6. Wet and warm conditions are the ideal environment for the causative agents of mud fever to develop (Source: Author). to wet environments (Figure 6) and skin trauma are the two and Biotin will support skin health from within. Quality main predisposing factors. Prognosis for average cases is protein is also an essential requirement as 80-85% of hair good with a relatively simple course of treatment, however, is composed of protein. Supplementation of antioxidants owners should aim to prevent the issue where possible. to the diet in the form of Vitamins C and E can also help Eliminating the primary, underlying cause will usually “mop up” free radicals in the body and ease itchy, irritated result in a quick recovery and ideally, no recurrence skin. Furthermore, Omega-3 fatty acids are known for their of the condition. Orsolya Losonci BSc (Hons), EEBW, Member of the IAABC and IEBWA Orsolya Losonci did her BSc in Equine Behavioural Science at Writtle University College where she became passionate about equine nutrition and rehabilitation. She qualified as an equine behaviourist, nutritionist and bodyworker in 2020, the same year she launched her company, HORSI. She has been around horses since the age of 5 and has been working with horses with problematic behaviours since 2015. She has trained a range of equines from feral to actively competing horses of all age groups as well as World Horse Welfare rescue horses for rehoming. She night watched pregnant and lactating mares and their foals and took part on numerous CPD events to extend her knowledge about horses. In 2020 she got an Entrepreneurial Excellence Award for her successes in the industry and for her international dissertation project. She provides educational content to horse owners on social media and is the Hungarian Language Leader at Equitopia. She is based in England and Hungary, providing a holistic approach to client horses while doing her MSc in Animal Nutrition at the University of Glasgow. “My aim is to make this world a better place for horses and to help as many as come my way.” REFERENCES Ashton, S. (2020). How to Treat Mud Fever. EverythingHorse. [online]. Available from: https://everythinghorseuk.co.uk/how-to-treat-mud-fever/ [Accessed November 22, 2021]. Aufox, E., Frank, L., May, E., & Kania, S. (2018). The prevalence of Dermatophilus congolensis in horses with pastern dermatitis using PCR to diagnose infection in a population of horses in southern USA. Veterinary Dermatology, 29(5): 425-e144. Cullinane, A., Barr, B., Bernard, W., Duncan, J., Mulcahy, G., Smith, I., & Timoney, J. (2006). The Equine Manual. 2nd ed. Davis CA: Elsevier. Dharmshaktu, G., Singhal, A., & Pangtey, T. (2016). Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds. Journal of Family Medicine and Primary Care, 5(1): 175–177 Frye, C., Bei, D., Parman, J., Adam, J., Houlihan, J., & Rumore, A. (2019). Efficacy of Tea Tree Oil in the Treatment of Equine Streptothricosis. Journal of Equine Veterinary Science, 79(1): 79-85. Geor, R., Harris, P., & Coenen, M. (2013) Equine Applied and Clinical Nutrition. 1st ed. Edinburgh: Elsevier. Hamid, M. (2016). Skin Diseases of Cattle in the Tropics. 1st ed. London: Academic Press. Kim, Y., & Shin, D. (2005). Volatile components and antibacterial effects of pine needle (Pinus densiflora S. and Z.) extracts. Food Microbiology, 22(1): 37-45. Knottenbelt, D. (2012). The Approach to the Equine Dermatology Case in Practice. Veterinary Clinics of North America: Equine Practice, 28(1): 131-153. Marsella, R. (2019). Manual of Equine Dermatology. 1st ed. Oxfordshire: CAB International. McDowell, R., & Rowling, D. (2003). Herbal Horsekeeping. 1st ed. London: J. A. Allen. Nicholson, W., Sonenshine, D., Noden, B., & Brown, R. (2019). Medical and Veterinary Entomology. 3rd ed. Starkville MS: Academic Press. Pilsworth, R., & Knottenbelt, D. (2007). Skin Diseases Refresher. American Association of Equine Practitioners. Schwarcz, J. (2019). Does Taking “Colloidal Silver” Have Health Benefits?. Mc. Gill. [online]. Available from: https://www.mcgill.ca/oss/article/health-you-asked/does-taking-colloidal-silver-have-health-benefits [Accessed November 22, 2021]. Scott, D., & Miller, W. (2011). Equine Dermatology. 2nd ed. Ithaca NY: Elsevier. Self, H. (2005). Veteran Horse Herbal. 1st ed. Buckingham: Kenilworth Press. SevernEdge (2021). Under The Skin: The Truth About Mud Fever. Severn Edge Vets. [online]. Available from: https://www.severnedgevets.co.uk/equine/advice/under-skin-truth-about-mud-fever [Accessed November 22, 2021]. Underwood, W., Blauwiekel, R., Delano, M., Gillesby, R., Mischler, S., & Schoell, A. (2015). Chapter 15 - Biology and Diseases of Ruminants (Sheep, Goats, and Cattle). In Laboratory Animal Medicine. London: Academic Press. Varró, A. (2006) Gyógynövények gyógyhatásai. 1st ed. Debrecen: Black & White Könyvkereskedés Kft. Välimaa, A., Honkalampi-Hämäläinen, U., Pietarinen, S., Willför, S., Holmbom, B., & Wright, A. (2007). Antimicrobial and cytotoxic knotwood extracts and related pure compounds and their effects on food-associated microorganisms. International Journal of Food Microbiology. 115(2): 235-243. VeterianKey (2016). Dermatophilosis. Veterian Key. [online]. Available from: https://veteriankey.com/dermatophilosis/ [Accessed November 22, 2021]. Yarnell, K., Le Bon, M., Turton, N., Savova, M., McGlennon, A., & Forsythe, S. (2017). Reducing exposure to pathogens in the horse: a preliminary study into the survival of bacteria on a range of equine bedding types. Journal of Applied Microbiology, 122(1): 23-29. Zeng, W., He, Q., Sun, Q., Zhong, K., & Gao, H. (2012). Antibacterial activity of water-soluble extract from pine needles of Cedrus deodara. International Journal of Food Microbiology, 153(1-2): 78-84. 34 35Glossary Ad libitum A diet that is available at all times to the horse. A solution which prevents the growth of bacteria and fungi in superficial wounds on Colloidal silver the skin. A space between the teeth which is normally not present and can cause discomfort Diastema when feed becomes stuck in it. Diastemata The plural of diastema. Warm blooded animals which can regulate their own body temperature due to Endotherm metabolic processes in the body. Equine odontoclastic A dental disease affecting the incisors of the horse, specifically the structure of the tooth resorption and teeth, causing inflammation in surrounding gums. This disease mainly affects hypercementosis (EOTRH) older horses. Heat increment The heat that is produced due to consumption and processing of feed. Branches found in fungi which serve as structures important for growth in fungi. Hyphae These branches together are referred to as mycelium. REP Teeth that will continue to erupt throughout the horse’s life to replace the tooth that A Hypsodont P has been worn down due to grinding feed. DEL A funnel like structure which is filled with cement and only found in the horse’s C Infundibulum Y upper cheek teeth. CE Mastication The process of chewing feed. R % A skin condition caused by bacteria in combination with irritation from mud. Most 00 Mud fever 1 commonly seen on the legs of the horse. NO A swelling caused by retention of fluid in body tissue. Usually accompanied by Oedema D inflammation. ETN Pro-inflammatory A substance capable of causing and/or promoting inflammation. IRP Quidding A clinical sign of a dental problem where horses drop bits of food while chewing it. A skin condition caused by bacteria after being exposed to wet environments for a Rain scald prolonged time. Saturated fatty acid A fatty acid that does not contain double bonds. Mainly in food from animal sources. A fatty acid with less than six carbon atoms, obtained from indigestible foods via Short chain fatty acids intestinal microbial fermentation. Short chain carbohydrates, such as starch or sugar, rapidly digested by enzymes. Soluble carbohydrates Found in higher levels in cereal grains. Also referred to as ‘fibre’ including cellulose, hemicellulose and pectin which make Structural carbohydrates up the cell wall of the plant. These are digested through microbial fermentation in the hindgut of the horse. The process of regulation of optimal body temperature through different Thermoregulation environmental temperatures. A fatty acid which contains one or more carbon chains with double bonds. Mainly in Unsaturated fatty acids food from plant-based sources. Volatile fatty acids A group of fatty acids produced in the horse’s hindgut by cellulose digesting microbes. Zoospores A cell which is used as a way of reproduction by some fungi and bacteria. 34 35® Feedmark 42 YEARS AT THE CENTRE OF EQUINE NUTRITION 36 PB