Saccharomyces cerevisiae and nitrogenous supplementation in growing steers grazing tropical pastures

A grazing trial utilizing 42 individually supplemented growing steers (190 +/- 80 kg initial BW) was conducted to study the effect of Saccharomyces cerevisiae (SC; 0 or 10 g per day) and two protein supplements on the performance of steers grazing in a mixed pasture 1 of tropical grasses during the dry season. 2 kg of supplement (DM basis) was offered daily (2.7-2.8% N) during the 90 days of the experiment. Nitrogen in supplements was administered from 100% urea, or 50:50% urea and meat meal, Treatments consisted in a grazing control group (CG), a group receiving 10 g per day SC (SC); and the supplements 100 and 50 U, with and without the yeast culture. Stargrass (Cynodon plectostachyus) was the main grass of the diet (72.3%) followed by Paspalum conjugatum (14.4%), Brachiaria mutica (8.9%) and others (4.4%). Non supplemented steers had lower (P < 0.01) ADG (0.700 kg per day) than those supplemented (0.840 kg per day). Animal gain (ADG) was similar to supplements containing meat meal (0.865 kg per day) or urea (0.815) without effects of Saccharomyces cerevisiae. Supplement intake with urea (0.688 kg per day) was lower (P < 0.01) than with meat meal-urea (1.333 kg per day) but forage intake was not affected. Total tract digestibility of NDF and ADF were not affected by treatments. In conclusion Saccharomyces cerevisiae did not improve either animal performance or fiber digestibility. Growing ruminants grazing tropical grasses in dry season showed a positive response to nitrogenous supplementation. (C) 2000 Elsevier Science B.V. All rights reserved.