There is a paucity of information on the digestion and utilisation of feeds by horses. Currently, most diets are formulated according to NRC (1989) recommendations which assume digestibility coefficients: for example, a digestibility coefficient for crude protein of 0.46 is used for animals at maintenance compared with 0.55 for lactating mares. However, if the digestibility of diets is uncertain, then use of such assumed values could result in either the under- or over-supply of nutrients. Furthermore, knowledge of the site of digestion is important. For example, only dietary protein digested and absorbed in the proximal small intestine can be efficiently utilised by the horse and the digestion of carbohydrate in the foregut (in terms of ATP yield) is more efficient than its fermentation in the hind gut. Therefore, in order to formulate diets more precisely, it is important to know a) the site at which dietary components are degraded and b) the extent of this degradation. In the present study mobile bags were used to determine the extent of organic matter disappearance (OMD) and crude protein disappearance (CPD) from four botanically diverse feedstuffs in the foregut of caecally - fistulated ponies.