By definition these are nutrients which are degraded by the microbiota of the large intestine, and which have a beneficial effect on the gut flora whilst producing short chain fatty acids for absorbtion which is of benefit to the host organism. In essence these compounds feed the beneficial bacteria in the hind gut, selectively encouraging the expansion of their population which suppresses growth of the less beneficial or pathogenic bacteria. The effects on gut bacteria have ramifications for the whole body and may improve immune function, reduce chronic bowel inflammation / colitis, and possibly affect some cognitive functions and mood states such as anxiety, though these effects have yet to be clearly demonstrated in horses.
Prebiotics are made from a carbohydrates (plant fiber), specifically polysaccharides, chains of simple sugars bound chemically together. One of the first studied was Inulin, a form of fructan or fructo-oligosaccharide (FOS) which has chains of fructose molecules. Others include Galacto-oligosaccharides (GOS) and the more recently popular Mannan-oligosaccharides (MOS) which seems to exert a protective effect on the lining of the large intestine whilst promoting growth of the ‘’good bugs’’. However, most work on prebiotics has been done on other species such as pigs, poultry and humans and the capacity to positively manipulate the equine gut microbiota is still very much in its infancy.
Prebiotics can be used in place of, or together in combination with Probiotics.