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 (PO.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

Thirty six zebu steers (35 Gobra and 1 Maure), 2.5 years-old on average, were equally alloted in 3 groups fed different crop by-product based diets. For diets 1 and 2, molassed rice straw and molassed millet straw were offered ad libitum as a basal diet while the other ingredients were mixed and given (2.5 kg/animal/d) as supplement 1 and 2, respectively. In diet 3, all ingredients were mixed and given as a compound feed. The energy content was higher in diet 3 (0.83 FU/kg DM) than in diet 1 and 2 which were isoenergetic, 0.65 and 0.63 FU/kg DM, respectively. Animals were group-fed twice daily (at 08.00 and 16.00 h) during 3.5 months. Diets offered and refusals were daily measured. Cattle were monthly weighed, their body condition was scored using 2 scales of 6 (BCS 0-5 ) and 9 (BCS 1-9 ) points, and body lipids and energy were estimated. The level of intake of steers was 101, 94.3, and 148.3 g DM/d/BW 0.75 for the 1 rst , 2 nd and 3 rd groups, respectively. Groups 1 and 2 had average daily gain similar (ADG) (446.7 and 425.5 g BW/animal, respectively) and gain in BCS 0-5 (+0.8 points) and in BCS 1-9 (+1.9 points). A spectacular development of the hump was observed in cattle of the 3 rd group which was submitted to the richest diet. They also gained more (P<0.01) weight (AOG : 1012 g BW/animal), BCS 0-5 (+1.9 points) and BCS 1-9 (+3.5 points) than did the others groups. Increased rate of BW gain resulted in an acceleration of body lipids deposits (22.8 kg in the 3 rd group vs 11.5 kg in the 1 rst and 11.6 kg in the 2 nd group) and in gain in body net energy (936.6 MJ in the 3 rd group vs 473.9 MJ in the 1 rst and 490.3 MJ in the 2 nd groups). Each kg of gain in BW contains on average 264.7 g of lipids and 11.4 MJ of net energy.