In vivo nutrient digestibility in sheep, and rumen dry matter degradability in cattle fed crop by-product based diets

Abstract

Nutrient in vivo digestibility in sheep and rumen dry matter degradability in cattle fed cereal straw and concentrate-based diets were determined in two experiments. In Experiment 1, a conventional in vivo balance trial was conducted with six Peul-peul sheep to evaluate apparent digestibility of 3 diets. Diet 1 consisted of (g/kg DM): rice straw 560, molasses 115, rice bran 180, peanut cake 130 and mineral supplement 15; diet 2 contained (g/kg DM): millet straw 580, molasses 115, millet bran 175, peanut cake 113 and mineral supplement 15; diet 3 was a mixture of (g/kg DM) peanut hulls 180 and cake 50, molasses 200, maize grain 95, senal* 200, cotton seeds 250 and mineral supplement 25. In Experiment 2, the rumen degradation pattern of the feed ingredients was evaluated using the nylon bag technique in three fistulated Gobra zebu bulls successively fed the same diets. In vivo dry matter and organic matter digestibility were significantly (P<0.05) influenced by diet type and particularly cell wall digestion was higher (P<0.01) in the straw based diets (1 and 2) when compared with the mixed feed (diet 3). The animal did not influence (P<0.05) feed degradation profiles which were strongly (P<0.001) modified by diet and feed type. It was possible to classify different feed types according to their theoretical DM degradability (Dt) in low (Dt < 50% DM) and medium quality roughages (50 55 % DM) and concentrates (Dt>55 % DM). Treatment of straws with molasses (17%) significantly (P<0.01) improved their DM degradation. The feed average degradation profile was influenced by fibre content, especially lignocellulose (R= -0.76). Feed Dt can also be predicted by dry matter disappearance at 24 h incubation time (R=0.90) and from individual ingredients in the case of mixed feeds.