Aporte de energia, composição e eficiência microbiana em bovinos alimentados com feno de capim-marandu e concentrado balanceados para diferentes ganhos de peso e potenciais de fermentação microbiana

The experiment was carried out with the objective to evaluate the energy aport, microbial composition and efficiency of Santa Gertrudis young bulls, canulated in the rumen and duodenum, fed diets with palisadegrass hay and concentrates. A 4 x 4 latin square design was used, in which the treatments were composed by the concentrates adjusted for daily body weight gain (BWG) of 0.5 and 1 kg/animal and potential microbial fermentation (y) of 9.5 and 11 g microbial CP/MJ fermentable metabolizable energy. There were differences for the concentrations of total digestible nutrients (TDN) and fermentable metabolizable energy (FMEn) intakes, and for the composition in organic matter and mineral of ruminal bacteria for diets adjusted for different BWG. There was significant BWG x y interaction for TDN intake as percentage of body weight and in the CP and total carbohydrates composition of the ruminal bacteria. There were no differences for the potential microbial fermentation. The efficiency of microbial synthesis also did not differ among diets and showed values of 12.7 g microbial CP/100 g TDN and 9.2 g microbial CP/MJ FMEn. The observed differences did not justify the balancing of the concentrates for the different potential microbial fermentation evaluated.