The effect of feeding, in the rainy season, multiple supplements formulated with different sources of protein on nutritional characteristics of growing beef cattle was evaluated. Five Holstein-Zebu crossbred steers with initial live weight of 300 kg, fistulated in the esophagus and in the rumen, were assigned to five paddocks (0.3 ha) of Brachiaria decumbens in a 5 × 5, incomplete Latin square design, with 5 supplements and 4 periods in 4 (14 days). Supplements evaluated were based on soybean meal (SM), cotton seed meal (CS, 38% CP), corn gluten meal (CGM, 60% CP) and wheat bran + urea (WBU) and a control supplement, consisting only of mineral mix (MM). The amount of daily supplement fed was set to provide approximately 180 g of CP/day. Protein sources affect only the non-fibrous carbohydrates and CP intakes, which was higher when, was fed supplement based on cottonseed meal and lower when fed mineral mix. There was no effect of protein sources on the total and partial digestibility of nutrients. The pH and of ruminal nitrogen ammonia levels were not influenced by protein sources, but all values have remained within the limits of digestion of forage. Protein sources did not affect the microbial efficiency (9.96 g CPmic/100 g TDN), neither the concentration of plasma urea nitrogen (12.78 mg/dL), and urinary nitrogen excretion (NUr)(63.14 g/day).
digestibility; intake; microbial efficiency; supplementation
