The effects of partial substitution of soybean with urea or slow-release urea on finishing performance, meat quality, and digestion parameters of Nellore steers

The effects of substituting ~50% of the soybeans in the diet of finishing Nellore steers with either urea (U) and/or slow-release urea (SRU) on the steer performance and meat quality were assessed in two experiments. In the first experiment, 46 Nellore steers in a 104-day experiment (Exp. 1) were fed a Control diet with U or SRU or U+SRU. In Experiment 2 (Exp. 2), digestibility and microbial protein (MCP) synthesis were assessed in four steers by using a 4 × 4 Latin square design with 21-day periods. Four corn-based diets were used in both Exp. 1 and 2. (1) Control (CTL): 0% of non-protein nitrogen (NPN). (2) U: 1.66% of NPN. (3) SRU: 1.8% of NPN. (4) U+SRU: 1.72% of NPN. In Exp. 1, final bodyweight, average daily gain, dry matter intake, Gain to Feed ratio, carcass traits and steer meat quality were not influenced by the experimental diets. In Exp. 2, the apparent digestibility was similar for all diets, and the MCP synthesis was affected by dietary treatments (P = 0.065). The NPN treatments showed 25.5% more (P = 0.03) MCP efficiency (g microbial protein/kg of total digestible nutrient content consumed) than the CTL. We conclude that the partial replacement of SBM with U, SRU or U+SRU will provide similar animal performance without negatively impacting carcass and meat quality and improve the efficiency of microbial protein synthesis in Nellore cattle.