The objective of this work was to study the effects of the concentrate levels of the diet on the microbial efficiency, ruminal ammonia and pH, and endogenous nitrogen (N) losses. Four Nellore bulls, fistulated in the rumen, abomasum and ileum, were full fed diets with 25.0, 37.5, 50.0, 62.5, and 75.0% of concentrate and allotted to a randomized block design. The ruminal ammonia concentrations and pH were measured in the ruminal fluid samples in collections made before and 2, 4, 6 and 8 hours after the feeding. The maximum microbial efficiency of 28.62 g Nmic/kg OMDR was estimated with 48.86% of concentrate level of the diet. The efficiencies expressed in g Nmic/kg CHODR and g DMmic/kg CHODR, however, showed negative linear effect, while the efficiency expressed in g CPmic/100 g TDN was in an average 9.42. The estimated values for metabolic fecal nitrogen, the urinary endogenous N, and total endogenous N losses were, respectively, 5.17 g/DM intake, 389 mg/kg.75, and 260 mg/kg.75. The ruminal pH decreased linearly with the increase of dietary concentrate levels and collection times. The maximum ruminal amonia concentrations of 20.23, 25.46, 28.92, 30.59, and 30.48 mg/100 mL were estimated at 3.19 hours after the feeding, for the diets with 25.0, 37.5, 50.0, 62.5, and 75.0% of concentrate, respectively.
microbial efficiency; concentrate; pH
