A complete pelleted diet (table 1) containing 11 p. 100 of crude protein and 17 p. 100 of cellulose (ADF-lignine according to the method of Van Soest) was distributed to ponies and rabbits. Total digestibilities, partial cumulative digestibilities in different compartments of the digestive tract (stomach, small intestine, caecum, proximal and distal colon) and changes in biochemical composition, measured by pH, VFA, lactic acid and ammonia concentrations, were compared. Total digestibilities (table 2). There was no significant difference in dry matter between the two species. Crude protein digestibility was higher in ponies, but a greater difference was observed for crude fiber digestibility: digestibility in the rabbit was 60 p. 100 of that in the pony. Starch was entirely digested in ponies and rabbits. Partial digestibilities (table 3). The dry matter content was the same in the stomach, the different parts of the small intestine and the caecum of both species. Starch was rapidly digested, but crude protein digestibility was highly negative in the stomach, small intestine and caecum of both species. Changes in biochemical composition (table 4). VFA concentrations were higher in the caecum and colon of ponies but molar percentages of acetic, propionic and butyric acids were very comparable (fig. 1); L-lactic acid concentration was higher in the first part of the digestive tract of ponies and ammonia concentration was lower.