INTAKE, DIGESTIBILITY, NITROGEN-BALANCE AND CERTAIN RUMEN CHARACTERISTICS OF ETHIOPIAN MENZ SHEEP FED TEFF STRAW SUPPLEMENTED WITH COTTON SEED CAKE, DRY SESBANIA, DRY LEUCAENA OR FRESH LEUCAENA

Twenty five rumen fistulated Ethiopian Menz sheep were used in a compl etely randomized block design to determine roughage utilization when d ifferent types of supplements (sesbania, leucaena, cotton seed cake (C SC)) and forms (fresh or dry leucaena) were fed. The chemical composit ion, intake, digestibility, nitrogen balance and rumen degradability c oefficients were determined. Rumen pH and ammonia-nitrogen (NH3-N) lev els were estimated in samples taken at 1, 2, 3, and 6 h after feeding. There was substitution of teff straw dry matter by the supplements. F resh leucaena effected the highest substitution. Supplementation enhan ced (p < 0.05) the dry matter degradation (DD) of teff straw at 6 and 12 hours of incubation but not (p > 0.05) for the other incubation tim es. There were no significant differences (p > 0.05) between treatment s in the degradation constants: readily soluble component (a) slowly d egradable fraction, (b) potential degradability (PD = a + b) and rate of degradation (C) and for rumen NH3-N concentration, the ranking was CSC > sesbania > dry leucaena > fresh leucaena > teff straw alone (p < 0.05). The particularly high substitution rate observed with fresh le ucaena might suggest that bulkiness may be a limiting factor in the in take of low quality roughages supplemented with tree leaves. The lower DM and OM digestibilities of the supplemented diets were attributed t o substrate preference by rumen cellulolytic bacteria. Excessively hig h levels of rumen NH3-N (328 mg/l) in the CSC diet resulted in high ur inary nitrogen losses (r(2) = 0.32; p < 0.001) leading to low N balanc e, This may suggest that for the utilization of poor quality tropical roughages, moderate levels of rumen NH3-N sustained over a longer peri od may be needed.