Horses are categorised as “hind-gut” fermenters as the majority of their energy derives from the fermenting and breaking down of fibre in the large intestine. This makes their ideal diet a predominantly forage-based one.

Roughage feeds also allow the horse to chew for prolonged periods of time, allowing for dental wear (as their teeth grow continuously until an old age) and reducing the chances of boredom-derived vices (it takes approximately 40 minutes for a horse to chew 1kg of hay compared to 10 minutes to chew 1kg of oats). It also stimulates salivation, gut movement and general gastrointestinal functions, all of which help to improve the overall wellbeing of the horse.

Roughage should therefore be the main component of a horse’s diet, with some individuals (usually ponies) not requiring any other supplements even when in hard work.

The roughage should be fed at around 1kg per 100kg body weight, split into 2-3 meals. The exact amounts will vary depending on the quality and nature of the roughage used. In general, the more a roughage matures before it is cut and dried, the lower the digestibility and higher the fibre content.

Grain should only be supplemented when the roughage does not provide adequate energy for the work demanded. Alternatively, vegetable oils can be used to provide energy without giving highly hydrolysable starch, contained in hard feeds/concentrates, which can cause an increase in body temperature. Therefore, it is not good if animals work or compete in warm countries and there is risk of rhabdomyolysis, also called tying up. Doses of oil can reach 400ml daily if they are split into multiple feeds, but must be introduced slowly and gradually to avoid inducing severe diarrhoea.

An adult horse needs approx 13-15MJ/100kg of body weight. This energy requirement increases in pregnant mares during the last trimester of pregnancy to 1.2 times the basal values. Young animals should not be overfed, as very rapid growth leads to unbalanced growth and predisposes to development of diseases such as osteochondrosis.

In general, roughage is rich in Potassium but does not contain enough sodium, so supplementing with 20mg/kg of BW daily of salt (Sodium Chloride) will control any deficit. This can be given in feeds or in form of a salt lick in the stable or field.

Calcium, magnesium and phosphorus are fundamental in growing animals and lactating mares and are usually not deficient in adults that are fed good quality roughage (legume hays are rich in calcium and phosphorus is present in high quantities in grains).

Other supplements include fat soluble vitamins such as vitamins A, D, E and K. These are present in all grain feeds, as well as in molasses, alfalfa hay and wheat bran.

The Society for the Protection of Animals Abroad (SPANA) is an animal charity looking after the welfare of working animals in some of the world’s poorest countries. Visit their website for more information and advice on horse welfare.