Generalities in equine nutrition and weight management

To better understand the equine nutrition and the role each organ has, we are going to first do a quick review of the physiology of the gastrointestinal tract.

Mouth In the mouth is where chewing and saliva production take place. Saliva acts as an important lubricant and gastric buffer (stabilises the pH of the stomach making it less acid). In horses it is only produced when they chew. This is a complex cycle that helps to reduce particle size and releases soluble components to the stomach, which will allow optimal digestion. A proper chewing movement is achieved when dentition is healthy, so this is one of the reasons why dental health must be kept up to date.

Stomach. The stomach of a 500kg horse has a volume of 8-15L and it has two types of mucosa (which is the inner layer of the stomach wall) a squamous superior mucosa and a glandular bottom portion. Secretion of hydrochloric acid, pepsin (they act in the initial digestion of proteins) and gastrin (enzyme that stimulates secretion of HCl) participate in the breakdown and initial digestion of food particles. Acid production (that can continue even in empty stomach) and the rate of food passage to the small intestine play a role in the appearance of gastric ulcers. For this, small regular forage meals are advised.

Small intestine (Duodenum, jejunum and ileum). Horses have approx. 20 metres of small intestine, which is quite short in length compared to its body size. It is the primary site of digestion and absorption of fats, proteins and non-structural carbohydrates (molecules with simple bonds like starch and sugar that can be digested by horse’s enzymes) as well as the majority of minerals and fat-soluble vitamins. This is achieved thanks to the secretion of different enzymes and the absorption that is made by the cells of the intestine.

The food transit is quite fast and all the nutrients that are not absorbed here will pass to the large intestine. However, this can have a bad impact in the intestinal health if high quantities of food are given at once. That is one reason why big amounts of food are not recommended.

Large Intestine (cecum, colon and rectum). As with any other domestic animal, horses don’t have enzymes capable of breaking down structural carbohydrates (complex molecules of fibre) and making them suitable for absorption. This is made by bacteria and protozoa in the large intestine. These microorganisms will digest fibre and other products coming from the small intestine by fermentation. The end products are different volatile fatty acids (VFA) that provide a source of energy to the horse. Bacteria are adapted to a certain pH maintained by the concentration of the VFA, so big amounts of starch and sudden changes on diets could alter it causing bacterial sufferance. This could lead to different conditions such as colic, laminitis and diarrhoea. Horses that might need high sugar inputs should have them in low quantities and frequently. In addition, as with any change in the diet, it should be introduced gradually over 2-3 weeks.

How much should I feed my horse? Remember that there is an important variability between horses and therefore there is not one single way to feed horses appropriately; feeding management needs to be tailored to each horse and his circumstances. However, forage/roughage (structural carbohydrates) should be the basis in a horse’s diet.  This can be given in the form of grass, hay, haylage, chaff and other forms. Many horses don’t need any other source of energy.

To understand the contribution of each type of feedstuff in fibre quantity we use the term dry matter (DM). General recommendations are that horses should receive a minimum of 1.5-2% of their body weight in dry matter, which means that a 500kg horse with no dietary restrictions should have 7-11Kg of hay daily. But this is not going to be the same amount in grass or haylage, as they contain more water. Another very important thing to take into account is that roughage is not nutritionally complete so even if your horse does not need any other form of energy you should always provide him with additional proteins, minerals and vitamins that can be achieved with forage balancers.

The physiology of the horse has always been well adapted to feral conditions, in which horses used to maintain a regular and balanced weight variation between summer and winter. However, our domestic horses do not have the same conditions anymore and together with the predisposition of certain breeds and ponies this has led to a continuous weight gain where the last consequence is the big increase in obesity.

Why is it a problem? Obesity can entail several conditions that affect horse well-being, such as mechanical and thermal stress, poor reproductive efficacy, predisposition to colic and laminitis, insulin resistance, lipid disorders…

What can you do? First of all, analyse your general situation and see if your horse is overweight. You can use the body condition score (BCS) system, which is based on the fat deposit of your horse’s body, in conjunction with the weight tape to monitor weight changes. Once you have categorized your horse as being overweight, have a look at your horse’s routine, food consumption, which type is it, level of exercise, how long is he grazing…

Regarding food management you can consider avoiding hard feed, changing the type of forage or reducing its amount, soaking the hay for 6-8 hours, slowing the intake of forage using double-netted hay, splitting it and placing it in different areas, using toys as hay balls. Reductions to less than 1.5% of the body weight in DM should be overseen by a vet and regular access to small quantities of forage and water must be assured to avoid colic and gastric ulcers.

Reduce grazing is another important but challenging measure: limit paddock size (strip graze), limited or short grass paddocks (they may need supplementary forage, don’t forget to ensure poo picking, appropriate worming), sand paddocks, reduce grazing time (consider that horses can be very fast eaters and ingest a big amount in less time), use a grazing muzzle. Keep in mind that some ponies are very clever and manage to take it off, some horses can develop sores with it or get nervous, so make sure not only that your horse is not stressed, but also that he is able to drink with it. You should also remove and check it regularly!

Exercise: this is also very important. Start with light exercise and increase gradually the intensity, duration and frequency per week. Try whatever is easier for you, ridding, longing, horse-walker but keep a track of it so see your progress.

Winter weight loss: it is a natural process so let’s take advantage of it. Let your horse out without rugs, consider hunter clip.

**Don’t forget that not all the measures are suitable for every horse and that all changes should be introduced slowly. Remember that food restrictions must be taken with caution and make sure your horse has regular access to water. It is essential to know that weight loss is a slow process that requires a lot of patience, so don’t give up. We also encourage you to contact us for any questions you may have or to seek for advice**