The digestion by sheep of barley and maize-based diets containing either meat and bone meal or soya bean meal

Abstract

An experiment is described in which 4 sheep, equipped with rumen, duodenal and ileal cannulae, were given diets consisting of pelleted alkali-treated barley straw (278 g dry matter (DM) kg −1 diet DM) and one of four ground and pelleted concentrate mixtures (722 g DM kg −1 diet DM), containing either barley and meat and bone meal, barley and soya-bean meal, maize and meat and bone meal or maize and soya bean meal. The diets were formulated to be isoenergetic and isonitrogenous and were given according to a 4 × 4 Latin square experimental design. The digestion of organic matter (OM) by the sheep was similar for all diets fed except that the proportion of the digestible OM intake apparently digested in the rumen was significantly ( P < 0.05) less when the maize rather than the barley-containing diets were fed. There were no significant differences between the protein supplements in the quantities of non-ammonia nitrogen (N) or amino acid-N entering the small intestine daily. However, the quantities of total N ( P < 0.001) and amino acid-N ( P < 0.01) leaving the terminal ileum and of total N voided in the faeces ( P < 0.01) were greater when meat and bone meal rather than soya bean meal was fed. Thus, apparent N digestibility ( P < 0.05) and the proportion of both total N ( P < 0.01) and amino acid-N ( P < 0.01) entering the small intestine apparently digested therein were greater when soya bean meal rather than meat and bone meal was fed. The apparent efficiency of microbial N synthesis in the rumen was not significantly different between diets and the values obtained ranged from 20.4 to 24.2 g N kg −1 OM apparently digested in the rumen. The quantities of feed N entering the small intestine daily were greater ( P < 0.01) and thus apparent feed N degradability in the rumen was lower ( P < 0.05) when meat and bone meal rather than soya bean meal was fed.