The equine gastro-intestinal tract: An overview of the microbiota, disease and treatment

Horse is a hindgut fermenter, i.e. most microbial activities take place in the large intestine which constitutes approximately 60 per cent of the gastro-intestinal tract (GIT). The feed reaches the large intestine after approximately 3 h and is fermented for 36–48 h in the caecum. This rate of transition is only possible if the roughage component of the feed is kept optimal. A diet rich in starch leads to an imbalance in gastro-intestinal microbiota, which may lead to colic and often death. Lactic acid bacteria form a major constituent of the microbiota in the GIT, especially in the large intestine, and produce most of the volatile fatty acids (VFA) needed for energy. Production of antimicrobial compounds, including antimicrobial peptides (bacteriocins) may prevent the growth of pathogens and keep a healthy microbial balance in the GIT. Lactic acid bacteria may also play a role in stimulation of the immune system.