Supplementation of grazing heifers with different protein sources

Objective. Evaluate the effects of supplementation with different protein sources (soybean meal and wheat bran with urea) on the productive performance, intake, digestibility, microbial protein synthesis, and metabolic profile of grazing beef heifers. Materials and methods. Were used twenty Nellore heifers at 8.5±0.06 months of age, with an initial average body weight of 241.5±4.71 kg. The animals were distributed in a completely randomized deseing with two treatments and ten replicates. Two protein sources in the supplements were evaluated: 1) Soybean meal (SBM), and 2) Soybean meal + Wheat bran + Urea (SBM+WB+U). Results. Crude protein (CP) and organic matter intakes were higher (p<0.05) for heifers from SBM compared with SBM+WB+U. The CP digestibility was increased (p<0.05) with SBM supplementation. Mean blood concentrations of glucose, cholesterol, serum urea nitrogen, and total proteins were not affected (p>0.10) by protein sources. In the same way, daily weight gain and final body weight were not influenced (p>0.10) by protein sources. Conclusions. The supplementation with soybean meal or wheat bran with urea in association with soybean meal in multiple supplements for grazing cattle provides similar productive and nutritional performance and metabolic profile in beef heifers.