The objective of this experiment was to evaluate the effect of utilization of soybean meal or corn gluten meal on in situ ruminal degradabilities of diets, based on coastcross hay, corn and one of the nitrogen sources, fed to bulls, with average weight of 650 kg. Corn gluten meal was considered as a nitrogen source of low degradability and the SBM as intermediate ruminal degradability. They presented nitrogen potencial degradability of 39.7 and 90.3% and effective degradability of 35.7 and 62.9, for the corn gluten meal and soybean meal, respectively. It was used mordant fiber to determine the rate of passage of the diets and it was obtained 6.6%/h for diets with soybean meal and 2.4%/h for diets with corn gluten meal. There was no difference in the potential degradability of the dry matter of the hay, in the fractions A, B, C and in the degradation rate, but the effective degradability of dry matter was lower for diets with soybean meal (29.3 vs 40.6%). For the nitrogen the ingredients, except corn, presented marked differences among diets in the fractions of degradability, in the degradation rate and in the effective degradability, being inferior in the diet with corn gluten meal. The corn differed only in the effective degradability of the nitrogen, being superior in the diet with corn gluten meal (68.7 vs 56.3%). The corn-starch presented lower effective degradability in the diet with soybean meal (52.5 vs 68.0%) and the effective degradability of the hay fiber also was inferior for these diets (27.3 vs 43.2%). It was concluded that nitrogen sources with distinct degradabilities can affect the degradability of the fiber of the roughage, as well as the degradability of the starch of the nitrogen source or the corn of diets.
fiber; nitrogen; nitrogen sources; ruminal degradability; starch
