Zebu cattle fed dry distiller's grain or cottonseed meal had greater nitrogen utilization efficiency than...

This study evaluated intake, apparent digestibility, ruminal parameters, nitrogen balance, and microbial protein synthesis in grazing beef cattle fed a mineral mix or combination of two coproducts (cottonseed meal and dried distiller's grains (DDG)) during the wet season. Urochloa brizantha cv. Marandu pastures were managed under continuous stocking to maintain a fixed grazing height of 25 cm using put-and-take methodology. Eight rumen cannulated Nellore steers were used to evaluate the different supplementation strategies. The experiment was composed of four treatments: (1) mineral mixed (MM; ad libitum); (2) energy-protein supplement using corn grain (energy) and cottonseed meal (protein; CS); (3) energy-protein supplement with 50% of the cottonseed meal replaced by DDG (50DDG); and (4) energy-protein supplement with 100% of the cottonseed meal replaced by DDG (100DDG). Except for MM, all supplements were supplied at a level of 0.3% of body weight (BW). A double Latin square was the experimental design performed, with eight cannulated animals, four treatments, across four experimental periods. There was a difference between dry matter and nutrient intake among treatments. The nitrogen balance was different between MM and the other treatments. There was a linear decrease in the rumen ammonia nitrogen levels under CS, 50DDG, and 100DDG. There were no treatment effects on the other parameters evaluated (P ≥ 0.10). Replacing the protein source in the supplement composition did not affect the metabolic parameters and the microbial protein synthesis. Supplementation at a rate of 0.3% BW, compared to MM supplementation, increased the nitrogen utilization efficiency in grazing cattle.