Supplementing for the winter Months – Selenavite E
Professor Jo-Anne Murray
PhD, MSc, PgDip, BSc (Hons), BHSII, RNutr, PFHEA University of Glasgow Veterinary School
Many of us will know the Pony/Riding Club and/or British Horse Society rules of feeding, but this article adds the reasons behind these recommendations to help understand the importance of these guidelines.
1. Feed little and often.
This rule is important for a few reasons. Firstly, you may recall from my previous articles that a horse’s digestive system is designed to process food on an almost continual basis. Consequently, the horse has a relatively small stomach for its size and also the small intestine, where enzymatic digestion of protein, starch, sugars and fats takes place, has a limited ability to digest starch. This means that if you feed your horse a large bucket full of feeds that are high in starch; for example cereal grains (oats, barley, maize) or a concentrate mix that contains high levels of starch, then some of the starch will bypass digestion in the small intestine and it will enter the hindgut where it will be rapidly fermented by the microbes. If a lot of starch reaches the horse’s hindgut then this can cause a disturbance to the microbial populations and may reduce the pH, which can also lead to reduced fibre digestion and, in some cases, colic. As a rule, a 500kg horse should not be fed more than 2kg of a feed containing 25% starch in one meal. 2kg of a feed containing 25% starch equates to 500g of starch in that one meal. The guidance is that horses should receive no more that 1g of starch per kg bodyweight per meal, which is 500g for a 500kg horse.
Another reason for feeding little and often relates back to the fact that horses only produce saliva as a direct result of chewing, which means that the amount of saliva produced is proportional to the amount of chewing. Saliva is extremely important for maintaining a healthy stomach (see gastric health article) and therefore it is very important that horses have access to forage or pasture on almost continual basis and not be fasted for anymore than 3 hours at a time. From a welfare point of view, horses are instinctively motivated to chew and if they are left without forage for significant amounts of time then this can result in stress and the possible development of stereotypic behaviours, such as crib-biting.
2. Feed plenty of roughage/fibre.
In addition to what I have discussed in the previous point related to the importance of forage in your horse’s diet, another aspect is the hindgut. In contrast to the small intestine, digestion and absorption in the hindgut is dependent on microbial fermentation of undigested feed residues leaving the small intestine, the main end-products of which are the volatile fatty acids (VFA); acetate, propionate and butyrate, and the gases carbon dioxide (CO2) and methane (CH4). The VFAs that are produced as a by-product of fermentation are then absorbed across the gut wall and are used as an important energy source by the horse. Structural carbohydrates, i.e. those associated with the plant cell wall (fibrous fraction of the plant), undergo microbial fermentation in the large intestine as the horse lacks the endogenous enzymes required to digest these plant constituents. In fact, the hindgut is designed to digest fibre and it is when non-fibrous substrates, such as starch and fructan enter, that problems can arise.