Avaliação de diferentes fontes e teores de proteína na dieta sobre o desempenho, fermentação ruminal e parâmetros sangüíneos de vacas da raça Holandesa em final de lactação

Four lactating Holstein cows were used in a 4x4 Latin Square design to evaluate the effects of levels (10.5% vs. 13.7%) and sources (soybean meal - SBM vs. urea - U) of protein on lactation performance, rumen fermentation and blood parameters. The treatments were: (A) 10.05% CP diet - SBM; (B) 10.05% CP diet - U; (C) 13.70% CP diet - SBM+U; (D) 13.70% CP diet - SBM. Dry matter intake, feed efficiency, milk production, milk protein content and yield were not affected (p > 0.05) by treatments. Milk fat content increased (p < 0.05) with 10.05% CP - U diet (treatment B). The increase of dietary crude protein content increased (p < 0.05) ruminal ammonia N, PUN, total VFA and decreased (p < 0.05) ruminal acetate.