R. Bras. Zootec.01/Oct/2004;33(5):1316-24.
Ruminal parameters and DM, CP and NDF forage disappearance of supplemented steers under grazing, during the dry season
DOI: 10.1590/S1516-35982004000500025
The objective this work was to evaluate the effect of protein supplements with three degradability levels (high-70%, medium-50% and low-30%) at three levels (0.5, 1.0 and 1.5 kg/day) on the ruminal pH, N-NH3 and DM, CP, NDF degradability of forage fed steers grazing Brachiaria brizantha cv. Maradu, during the dry season. The experiment design was a randomized complete block with three replications (grazing periods) and the supplement treatments were arranged in a factorial 3×3. Ten rumen-fistuled steers with 354 kg live weight, were used. There was not effect of the protein degradability and/or level of supplementation on the ruminal pH values with variety from 6.38 to 6.91. The concentrations of N-NH3 ruminal increased as the degradability and levels of supplementation increased, and were higher one hour after feeding, and decreasing until five hours. The control showed N-NH3 concentrations within the limits considered adequate for a good microbial activity. There was no effect of the protein degradability and/or level of supplementation on the CP and NDF ruminal degradation of forage, and these values were not different from the control, where 29% CP constituted the soluble fraction and 47% was the insoluble potentially degradable, with the rate of degradation of 4.88%. NDF was 56% potentially degradable at the rate of 4.33%.
Keywords: degradability; N-NH3; NDF; protein; supplement; tropical forage