Raçoes com diferentes teores de proteína degradada no rúmen para vacas em lactaçao. 1. Consumo, produçao e composiçao do leite

This work was carried out with the objective to evaluate then nutrient in takes and the milk production and composition of cows fed diets with different contents of rumen degraded protein (RDP). Twelve lactating cows 60 days post-calving, were fed with corn silage (Zea mays L) ad libitum and 1 kg of concetrate ration for each 2.5 kg of produced milk, on a complete reversal switch-back design. The percentage compositions of the diets were: R I - ground corn grain (GCG - 50.5), ground soybean gram (GSBG - 40.0) and cottonseed meat (CSM - 6.8); R2 - GCG (69.2), CSM (26.7) and urea (U - J)~ R3 GCG (42.6), CSM (53.9) and U (1) and R4 GCG (38.3)~ CSM (54.7). bone and meat rneal (3.0) and fish meat (3). Mineral supplement and antioxidant were added to all ration. The nutrient intakes were not affected by diets, although the cows fed with R, diet showed an increase of dry matter and organic rnatter intake and those cows fed R3 diet intaked more crude protein, neutral detergent fiber and acid detergent fiber. Higher other extract intake was observed when cows was fed R,I There were no influence of concentrate diet types on the milk production or 40 percent, fat corrected milk and milk fat content, however the milk protein content increased when the soybean was presented in the diet (RI). A positive effect of the rurnen non degraded protein on the milk protein content was observed. (RA)