Horses are non-ruminant herbivores, meaning that they don't have multi-compartmented stomachs like cows, sheep and deer.
The horse, much like a human, has a very simple stomach. The horse's digestive tract is very different from other mammals due to the fact that it digests parts of its feed with enzymes first in the foregut and then ferments in the hindgut.
The horse’s stomach is, in relation to other species, very small compared to their body size. Hence, feed and forage does not remain long in the stomach of horses, compared to humans for example.
The upper, non-secretory part of the stomach acts as an expansion vessel to allow consumption of high-volume forage. The chewed feed and forage enter the stomach, along with saliva (horses produce 10-12 litres of saliva per day) and is mixed with gastric secretions. The fibrous forage floats to the top of this liquid mixture, forming a mat that helps prevent acid splashing. The acid secreted in the stomach initiates hydrolysis of the protein, allowing the first enzymic reactions (the enzymes are activated in an acidic environment).
Acid-loving bacteria in the stomach initiate starch digestion, releasing volatile fatty acids, further adding to the stomach acidity. The dwell time in the stomach will depend on the type of feed (see above) but is typically shorter compared to other mammals, and may be as little as 20-30 min, according to some sources, although this is very variable.
On leaving the horse's stomach, the contents enter the jejunum and duodenum, then the ileum, which is the main site of absorption for protein and glucose.
The stomach contents are then subjected to secretions from the bile duct (horses do not have a gall bladder to store these compounds, so bile is continuously secreted) which initiates fat digestion. Pancreatic secretions in the duodenum contain enzymes and bicarbonate to further progress digestion and neutralise stomach acid. However, parts of the jejunum and duodenum may still be at risk from acid damage from the stomach contents, which have been reported in horses as ulcers, but remain difficult to measure in vivo due to accessibility.
The hind gut is the primary region of digestion in the horse, in an evolutionary sense. As horses are adapted to a high fibre, forage-based diet it must be able to digest such material.
Mammals lack enzymes to act on cellulose-based, vegetable matter, and so the equine caecum has developed to be a large chamber containing beneficial micro-organisms which have this ability. They act synergistically to digest fibre, resulting in energy rich, volatile fatty acids as well as important vitamins (especially B vitamins).
For modern horses fed grain and legume-based feeds, it is important that starch and protein is digested in the upper tract and their components absorbed in the ileum, as flow-through of such materials to the hind gut can promote undesirable bacteria, causing various metabolic and gastric problems.
Fructan sugars in lush grasses have been shown to cause laminitis in horses and ponies due to its activity in the gut (Pollitt et al., 2003) when fed in excess. To create a correct hind gut microfloral population, several issues need to be considered – early nutrition at weaning, introduction of beneficial bacteria, pH and limiting exposure to pathogens.
Imbalances in the hind gut can occur if very young horses are exposed to pathogens, especially at birth and weaning. This can lead to a lifetime of problems, such as poor weight gain and reduced maintenance of body condition, behavioural issues and repeat attacks of sub-clinical diarrhoea. Gastric upsets, resulting in e.g. diarrhoea, are caused when toxins from pathogens attach to the gut wall, rendering the lining cells unable to take up water and minerals, especially in the colon.
Effective administration of technical feed ingredients into the hind gut requires delivery into the lower region and for the ingredient not to be damaged by stomach acid. Hence, many of these ingredients may be encapsulated or protected on a carrier, or in an inert form that is unaffected by acidic conditions.
Use of Maxia Digest benefits the horse from three key aspects:
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