Separating the Effects of Digestibility and Palatability on Food Intake in Ruminant Animals

Abstract

IN ruminant animals fed exclusively on roughages there is a close positive association between voluntary food intake and the digestibility of the diet. It has been suggested that this association occurs because foods of high digestibility are cleared from the digestive tract—by absorption and the expulsion of undigested residues—at a faster rate than are foods of low digestibility¹. Foods which differ from one another in digestibility also differ in such other respects as chemical composition and physical structure, and the association between intake and digestibility (or rate of digestion) may not be entirely a causative one. In particular, differences in chemical and physical composition may affect the taste and texture of the food and thus its palatability. A ruminant may therefore eat more dried grass than straw, for example, not just because the former is more digestible but because it is also more palatable.