Dietary supplements for horses can be a complex area. It's not unusual to feel uncertain about what supplements can be combined safely and which cannot, and unfortunately there is also a great deal of misinformation that exists, making things confusing for horse owners.
However, it is true that mixing supplements in particular combinations can reduce their effectiveness, or in extreme cases even cause harm. This tends to be for one of two reasons; that a particular ratio between two ingredients needs to be met, or that feeding more than one supplement that contains the same ingredient can mean overfeeding that ingredient, rather than there being a particular combination that simply cannot be fed altogether.
Today we're taking a look at which horse supplements should not be mixed - or more specifically, those you should exercise caution with.
Horse supplement combinations to take care with
Minerals can interact in intricate and complex ways. It is possible for imbalances (whether excesses or deficiencies) to significantly influence the absorption, metabolism, and excretion of others. Here are some of the combinations worth taking care with when reviewing your horse's nutritional needs.
Copper and Zinc
Mistakes with the ratio of Copper and Zinc are some of the most commonly-encountered challenges when it comes to feeding multiple supplements. Feeding these minerals in the wrong ratio can inhibit their uptake and cause deficiency symptoms over time.
You may see it recommended that they are fed in a 3:1 ratio, but The National Resource Council’s Nutrient Requirements of Horses (2007) actually recommends that these minerals should be fed in a 4:1 ratio (four parts Zinc to 1 part Copper) for mature horses, to ensure proper absorption of both minerals.
Calcium and Phosphorus
The relationship between Calcium and Phosphorus is generally the most widely-known amongst horse owners. Both minerals are important for maintaining bone and overall health, but the combination of them should be in a ratio of 2:1 (two parts Calcium to one part Phosphorus). Calcium absorption can be affected if phosphorus consumption exceeds calcium intake.
If a horse's feed source is primarily made up of cereal grains such as oats, it can be particularly easy to fall foul of this. Grain sources can be high in particular micronutrients, and Phosphorus tends to be one of these.
Calcium and Magnesium
Calcium and magnesium work together in a balancing act within a horse's body, and this balance needs to be maintained in the diet too. The ideal ratio for these minerals is 2.5:1 to 3:1 (between two and a half and three parts calcium to one part magnesium).
In many cases, this range is achieved in a typical balanced diet and in this case there is no cause for change. However, if magnesium is being supplemented (as is most often done from a desire to calm the horse) then it is worth reviewing the level of calcium in the diet to maintain the optimum ratio.
Multiple supplements that contain fat-soluble vitamins
Fat-soluble vitamins (Vitamins A, D, E, and K) can accumulate in the horse's liver if consumed in excess over time, which can be detrimental and lead to potential health problems. This is because they are stored, rather than excreted easily (as water-soluble vitamins would be).
The specific effects of this depend on the vitamin/s being overfed and the individual horse. For example, a horse may consume lots of Vitamin E when pasture makes up a large portion of their diet, but there is no toxicity in Vitamin E, so this will not cause problems. However, Vitamin D has a lower safety margin. Consulting an expert for guidance is always recommended.
If you are concerned that you may be mixing too many supplements that contain fat-soluble vitamins and want to review this with a specialist, do get in touch with our Registered Nutritionist, Stephanie Hyland (MSc. RNutr.).
Multiple supplements that contain selenium
It is worth noting that selenium has a narrow safety margin, so in most cases it is not appropriate to mix horse supplements that contain this mineral. While it is required in trace amounts for proper immune function, reproduction and antioxidant activity, exceeding the recommended intake of Selenium can be toxic to horses.
Iron, Copper and Zinc
Iron, Copper and Zinc should typically be at a ratio of no higher than 4:1:3 (four parts Iron to one part Copper to three parts Zinc, although it is worth noting that higher Copper to Zinc is required in some circumstances).
High levels of Iron - or any one of the metal minerals - can block absorption of the others, as they compete with each other for absorption sites in the body. This is one of the reasons that chelated minerals are now favoured in feed and supplements; these are minerals bound to a protein molecule, which means that they are actively absorbed in the small intestine and pass by the sites of competition.
Additionally, Iron is well provided in forage, so horses already get lots; this is why feeding additional iron in the diet can throw this ratio out of sync.
If you're unsure about mixing horse supplements
You can find the recommended ratios for most vitamin and minerals combinations online, but for your own peace of mind and your horse's health, we recommend reviewing decisions about supplements to add to your routine with an equine nutritionist. If the topic is an unfamiliar one to you then there is a chance of interpreting information shared on the internet incorrectly - and unfortunately there are also unreliable sources to be found.
At Feedmark, we take pride in offering expert guidance on equine nutrition. Our Registered Nutritionist has over a decade of industry experience and specialised knowledge in equine science; she is well-placed to help with any queries you may have on supplementing your horse. Do call our freephone advice line on 0800 585525 if you would like assistance.
Personalised nutrition for your horse without mixing supplements
If you would like to mix several supplements to support your horse's needs or fill nutritional gaps in their diet but are having trouble with ingredient combinations, try our Bespoke All-In-One™ supplement.
Your supplement is perfectly calculated by our Registered Nutritionist to the exact levels that will meet their needs before being produced and mixed just for you. This allows you to give optimal nutritional support without the worry of overfeeding an ingredient, or getting any combinations or ratios wrong. It also saves you the hassle of ordering multiple products and scooping from lots of tubs at feeding time!