Efeito de bicarbonato de sódio, feno e baga？o "in natura" sobre a digestibilidade e o desempenho de zebuínos em crescimento alimentados com baga？o de cana auto-hidrolisado

crude sugarcane bagasse (bin) with and without the addition of sodium bicarbonate was evaluated as a substitute for grass hay as source of long fiber in ruminant diets balanced with high proportions of steam pressure treated sugarcane bagasse (bah, 17kgf/cm2 for 6 minutes). the basal ration (i) had 54% bah; 10% corn grain; 25% cottonseed meal; 8% grass hay, 0.9% limestone; 0.5% urea; and 1.5% mineral premix, dry basis. in rations ii and iii, grass hay was replaced by bin and bin plus sodium bicarbonate (1.1%, dry basis) respectively. nelore bull and heifer calves (18 animals each sex) with 199kg average weight and 11 months average age were used in a factorial design (3 rations and 2 sexes), with two animals per plot. the adaptation and experimental periods were 15 and 87 days respectively. the results for lwg (kg/day), dm intake (% lw), dm conversion (kg dm/kg lwg), and fecal ph were: 0.909; 2.79; 7.41 and 6.46 for ration i; 0.867; 2.65; 7.24; and 6.57 for ration ii; and 1.019; 2.88; 7.03 and 6.75 for ration iii respectively. ration iii was superior to rations i and ii for lwg (p < 0.05) and showed higher fecal ph than ration i (p < 0.05). bull calves were superior to heifer calves for lwg (1,044 vs 0,820; p < 0.01) and dm conversion (6.7 vs 7.7kg ms/kg gpv; p < 0.01). a significant negative correlation (p < 0.05) was observed between dm conversion and fecal ph (r =-0.50). the high levels of dry matter intake (2.8% lw), the low bah ph (2.9 to 3.4) and the apparent low rumination activity observed during the experiment suggest that rumen and lower tract ph can be limitant factors in diets with high proportions of bah as those used in this experiment.