The harder a horse works, the higher its need for vitamins and minerals.
By Larissa Bilston, B.AgrSc (Hons1)
Feeding high performance horses well is not rocket science, but the results can blow you out of this world!
Horses fed all the roughage, energy and protein they need to grow, work, play, repair and maintain their bodies can still lack vitamins and minerals. Don’t be fooled by a shiny coat - oils added to hard feeds and the natural fats in grasses make horses shine even when they are mineral deficient.
The harder a horse works, the higher the need for vitamins and minerals. Fresh pasture provides a high level of many vitamins and minerals. Unfortunately, many performance horses have limited access to quality pasture, usually due to being kept in stables or small yards at a training facility, or through seasonal shortfalls (including drought). This means that high performance equine athletes are often fed a lot of hay to meet their fibre requirements for healthy digestion.
Vitamin shortages are most common when hay or grains form a large part of the ration because vitamins are most abundant in fresh plants and do not store well in hay. Hay starts losing its vitamin content as soon as it starts drying out, but the mineral levels remain similar to the original plant from which it was made.
The vitamins required to allow an equine athlete to function at his or her peak are the B group vitamins and vitamins A, D, C and E. Of these, vitamins B and C are water soluble so they are not stored in the body and must be fed or manufactured daily.
Vitamin A is used for night vision, bone development and is vital for the mucus linings which are the body’s first point of defence against infection. Horses manufacture Vitamin A from plant beta carotenes in the diet. Beta carotene is very quickly oxidised from hay and must be supplemented (as Vitamin A, retinol or beta carotene) if horses are not grazing plenty of fresh pasture.
Vitamin D is used to protect bones and joints and maintain muscle function. It is produced by the body when oils in the skin are exposed to sunlight, so a supplement is advised when a horse is rugged or stabled full-time, or washed with shampoo regularly enough to remove skin oils.
Vitamins C and E are important antioxidants which neutralise free radicals in the body. High performance horses have an increased need for these vitamins because the stress of intense exercise creates more free radicals than the horse would encounter at a lower work level.
Vitamin E is considered an important antioxidant which may support muscle, nerve and immune function. Vitamin E works hand in hand with the micromineral selenium which also needs to be supplemented in a performance horse’s diet. Be careful not to overdose on selenium because horse requirements for selenium lie within a narrow range, and it is possible to overfeed it especially when feeding a suite of fortified hard feeds and supplements.
Vitamin C is the main antioxidant used by the body for respiratory and immune health. It can also recycle other antioxidants, particularly vitamin E. Healthy horses do generate their own Vitamin C supply, but additional supplementation is recommended for horses subject to oxidative stress.
Vitamin B - Horses use four of the eight B group vitamins (thiamin, riboflavin, niacin and pantothenic acid) to utilise energy from the carbohydrates and fats in the diet. Vitamin B is produced and used by bacteria in the hindgut. High performance horses often benefit from additional B group vitamin supplementation because the impact of high grain diets and exercise or travel stress can change the population of hind gut microbes and reduce vitamin B production. Good gut health and the use of prebiotics (especially ample fibre to ‘feed’ the bacteria) and probiotics (e.g. oral yeast sources such as Saccharomyces cerevisiae) are therefore important to support the gut microbes responsible for manufacturing B group vitamins and optimize energy utilization.
Biotin also belongs to the B group vitamin family and is well known for its role in hoof health. Biotin supplementation can assist some horses with thin, crumbly hoof walls to grow hoof faster and with increased hoof hardness but it does not happen overnight. A biotin supplement of 15-20mg/day needs to be fed for at least 10 to 12 months in conjunction with correct trimming before the full impact can be seen.
Performance horses need to be fed optimal levels of minerals to enable their bodies to function efficiently, allowing them to perform to their physical potential. When diets lack essential minerals, or the critical mineral ratios are not balanced, sub-optimal performance is to be expected.
Contrary to common opinion, horses grazing very healthy pasture will be mineral deficient unless they are fed a supplement designed to top up and balance the mineral levels of their roughage source. The type and degree of mineral shortages will depend on the nutrient status of the plants eaten which is not always closely aligned to soil mineral status.
Zinc, Copper, Iodine and Selenium are often deficient in an unfortified diet (a diet without added vitamins and minerals).
A correctly balanced diet will add the vitamins and minerals necessary to top the levels in the diet up to at least daily minimum requirements. It must also balance mineral ratios across the whole diet, taking the mineral levels of roughage, hard feeds and supplements into consideration.
Scientists have calculated the minimum level of each mineral required to avoid a deficiency and have estimated toxicity levels. These are published in the National Research Council (NRC) book “Nutrient Requirements of Horses” last printed in 2007 and also available as an open-access book on the internet. The NRC guidelines provide a daily minimum requirement for horses based on their weight, age reproductive state and work level.
It is often desirable to provide minerals at a level higher than the recommended daily intake (RDI) in order to keep minerals in balance relative to each other. Balancing mineral ratios is imperative because some compete with each other at absorption points in the digestive system. This means that it is possible for a horse to be deficient in one mineral even when the diet provides the daily minimum intake of that mineral, because the supply of a competing mineral is too high.
In other words, when one or more of the critical mineral ratios are out of balance they can create an induced deficiency of some minerals even if they are supplied at one hundred per cent or more of the RDI. Therefore the OPTIMAL level of each mineral will lie somewhere between the RDI and the toxicity level, at a point where they balance ratios with co-dependent minerals.
For example the level of total dietary calcium must exceed the amount of total dietary phosphorous because these minerals compete for uptake. It is possible for a high phosphorous diet to provide 100 per cent of the calcium RDI but still cause the horse to have a calcium deficiency.
Nutritionists also balance levels of magnesium against calcium as well as ensuring that copper, zinc, iron and manganese intakes are in the right proportions. It is also important to consider that absorption of some minerals can be affected by plant compounds such as oxalates or phytates.
Toxicity and unbalanced mineral ratios are most likely to occur when multiple fortified food sources (pellets or mixed grains) are incorporated into the ration without checking total mineral levels. The safety margin for selenium is much smaller and toxicity levels are more easily reached than for other minerals.
Benefits of correct vitamin and mineral nutrition
A well-trained horse fed a correctly balanced diet can develop strength, muscle and fitness, and perform and recover better than one trained on a vitamin and mineral deficient diet. Correct vitamin and mineral nutrition helps to optimize the function of all bodily systems, including the circulatory, digestive and respiratory systems through to the maintenance of joints, bone, hoof and muscle tissue.
Performance horse owners are often pleasantly surprised that a few changes in the mineral balance of the diet can lead to an increase in feed-use efficiency and a smaller feed bill! Just as a car’s engine may give more kilometers per litre when fuelled with a higher quality petrol that allows the engine to perform more efficiently, a balanced diet can mean that a horse needs less caloric intake each day to perform the same work.
Research in horses has demonstrated that organically chelated minerals are no more bioavailable than inexpensive inorganic mineral salts.
Horses deficient in B1 often have poor appetites and can be nervous or unsettled.
Impact of workload on requirements
The harder a horse works, the higher its need for vitamins and minerals. For example, a 500 kg horse at rest needs 20 g of calcium a day compared to a 30 g/day requirement for a light work load. The same horse in very hard work needs double his maintenance calcium requirement taking it to 40 g/day.
Similar trends exist for other key minerals such as phosphorous, magnesium, potassium, sodium and chloride. The requirement for sulphur, copper, cobalt, iodine, iron, manganese, selenium and zinc increases with work, but not to the same extent. For example, a resting 500 kg horse needs 100 mg of copper compared to the need for 125 mg when in heavy work.
Vitamins, minerals and joint health
Adequate vitamin and mineral supplementation also supports your horse’s joint health. Vitamins B6, C and E and the minerals manganese, copper and zinc are required to help the body build, maintain and repair joint fluids, connective tissues, muscles and bones. If you are feeding a joint supplement or glucosamine, make sure your horse is getting ALL the vitamins and minerals it needs each day to get the best result from joint supplements.
Story from Horse Deals Magazine February 2017