Derivados de purina e síntese de proteína microbiana em novilhos mantidos a pasto e suplementados com diferentes fontes de nitrogênio não proteico, em associação a enzimas fibrolíticas

Abstract

The purpose of this study was to evaluate the microbial protein synthesis in steers kept the grass supplemented with different sources of NPN, associated with fibrolytic enzymes. The experiment was conducted in the Animal Science sector of the Federal University of Grande Dourados. Were used three (3) crossbred steers with ruminal cannulas with average weight of 350 kg, kept on individual paddocks of Urochloa brizantha cv. Maranduarranged in 3 x 3 squaredesign, not contemporary. The treatments were protein supplementation by changing the NPN sources: UC (concentrate + conventional urea) and UP (concentrated + slow-realease urea). Mineral supplementation was used (SM) as control treatment. The animals were supplemented daily at the rate of 0.3% body weight (BW) of a protein supplementation with 38% PB. The SM control treatment was set at 100 g per animal/day. The data were evaluated of orthogonal contrasts being 1 contrast (SM x protein supplementation) and contrast 2 (UC x UP). Protein supplementation improved microbial protein synthesis of animals (P = 0.018), however the NPN source did not change the microbial N (g/day). The same behavior was presented to the purine derivatives. Protein supplementation to grazing animals improves the microbial protein synthesis of animals, but had no effect occurred for the NPN source in this variable.