An animal feed additive comprising a plurality of enzymatically active enzymes, the enzymes comprising a plurality of carbohydrases, for example one or one amylases and optionally one or more fructanases. This is typically used for equines and may be combined with oats or hay. This mixture has been found to be especially useful to prevent intestinal disease such as colic, acidosis and laminitis. The application also describes methods of monitoring the health of an equine, comprising measuring the concentration of one or more volatile organic compounds from the faeces of an animal selected from acetic acid, butanoic acid, propanoic acid, 2-methyl propanoic acid and 3-methyl butanoic acid.
