A group of fatty acids produced by microbial digestion of fiber in the hind gut of the horse including butyric, acetic, propionic and valeric acids. VFA’s can be absorbed through the wall of the caecum and colon and utilised as energy sources. The horse is adapted to process large amounts of relatively low quality fibrous forage feeds by utilizing the hind gut microbiota to convert plant energy, stored as complex carbohydrates like cellulose, into VFA’s for it’s energy supply. As much as 70% of total energy intake may come from VFA’s with the remainder from simpler carbohydrates like sugars and starch, plus protein and fats.