For last 5 weeks I have been following the online Equine Nutrition course offered by the University of Edinburgh. This course was given by Dr. Jo-Anne Murray who is a senior lecturer in animal nutrition at the Royal (Dick) School of Veterinary Studies at Edinburgh. I thought this course provided an excellent overview of the basics of equine nutrition and functioning of the equine gastrointestinal track. This course has also answered many of my questions regarding horse nutrition and feeding, and I feel now much more confident about making decisions about my horse’s nutrition requirements. In this blog I wanted to summarise some of the key pointers that I have learnt during the last 5 weeks. I hope they provide some insights to you too and may help you a little bit when you are next time are going to choose a new bag of food for your horse.
Horses are officially classed as non-ruminant herbivores, meaning that they rely on enzymatic digestion. In horses the enzymatic breakdown of food-stuff (namely sugars and starch) takes place in the small intestine. However, unlike in other non-ruminant animals (e.g. people) horses also digests a lot of grass and/or fibre. Horses cannot digest the fibre on their own but rely on fermenting microbes to do the job for them. These microbes (bacteria and protozoa) are permanently living in the large intestine of the horse, where they perform a vital task in horse’s nutrient digestion by releasing energy from fibre and thus helping to support horse’s energy requirements. These “good” microbes living in the large intestine, however, are very sensitive to sudden changes in a diet and especially to high levels of starch. So, if horses are fed high levels of starch (i.e. cereal grains) some of this may “escape” the small intestine and enter the large intestine. This in turn would lead to a change in the microbial population. The new “bad” microbes would start to break down the starch in the large intestine and produce large amounts of fatty acids. This process could lead to lowering of the hindgut pH and causing digestional upset.
In the wild 100% of the horses diet is made of forage (low quality grass and hay). This is also what the digestional track of the horses has evolved to deal with. Horses have also evolved to eat little and often, in nature grazing between 16-20 hrs a day. Thus, for optimum gut functioning forage should always provide the bases of every horse’s diet. Ideally forage would be provided in free bases, or to avoid any digestional upsets or colic horses should ideally not go unfed for much longer than 3 hrs at one time. In domesticated situations it can be tricky to provide forage on free bases and trying to mimic the natural behaviour can be difficult. However, making use of slow feeders can help to make the forage last longer. Slow feeders can also aid in unnecessary weight gain.
For many domesticated horses in recreational or light work forage, such as good quality haylage or hay, is sufficient to cover the daily energy requirements. Although, a feed balancer (i.e. supplement) may be needed to unsure that essential mineral and vitamin requirements are provided. In any case forage should cover minimum of 70% of the horse’s daily food ration and in no case less than 50%. Providing sufficient amount of forage and fibre are essential for the functioning of large intestine and health of the gastrointestinal track. If cereal grains or hard feed are given these should be fed little and often. This is because horse’s stomach is relatively small, having a capacity of around 2 litre. In addition, if too much cereal or starch is given in one go it may cause digestional upset. The starch digestibility of the small intestine is limited and if too much starch is fed in one instance small intestine may not be able to cope with it and starch may “leak out” into the large intestine.
So how much should you feed your horse? A good rule of thumb is that your horse should eat around 2% of its body weight everyday. So a horse that weights around 500 kg should eat ±10 kg of food-stuff a day. A point to note is that this calculation is based on dry matter content of the food-stuff, so if you are only feeding haylage and if haylage is ±30% water and ±70% dry matter your horse should in fact eat ±13 kg of haylage a day. Something to keep in mind though is that the water content and especially the nutrient content of grasses and hay vary a lot. For example, the sugar content in grass may vary from 3 to 30 % and energy content from 7.5 to 12 MJ/kg dry matter. Thus, no batch of grass/hay/haylage is the same as the next. Therefore, for horses which are suffering from laminates or equine metabolic syndrome and are sensitive to sugars, it is advisable to have your forage analysed. If your horse is prone to weight gain or cannot handle too much sugar, hay can also be soaked to leach out some of the sugars. Minimum of 3 hour soaking time is recommended for removal of sugars, although the amount of sugars leaching out can not be controlled. Therefore, if the sugar content of the hay is very high, to lower it to <10%, which is recommended for horses and ponies prone to laminates, can not be guaranteed. In contrast, if your horse finds it difficult to keep the weight on, energy or calories into the diet can be added, for example, by using oils or feeding sugar beat bulb (unmollassed). Sugar beat is also a great source of palatable fibre and is low in sugars/starch. However, if your horse is suffering from weight loss, it is also advisable to have their teeth checked or contact veterinarian for advice. And remember any change to your horses diet should be done gradually over period of days or weeks. Horse’s digestional track is sensitive to sudden changes and you want to keep those microbes happy!