PSX-23 - Effects of partial or total nitrogen replacement of soybean meal with urea on intake, digestibility and nitrogen balance in growing Nellore × Red Angus bulls

Abstract: In feedlot systems, feeding non-protein nitrogen sources, such as urea, instead of true protein sources, such as soybean meal (SBM), could be an alternative way to reduce dietary costs. This study aimed to evaluate the effects of partial or total replacement of SBM by urea on feed intake and apparent total-tract digestibility of organic matter (OM) and crude protein (CP), and on nitrogen (N) balance in bulls. Four Nellore × Red Angus crossbred bulls (292 ± 14.6 kg BW) were randomly assigned to treatment in a 4×4 Latin square design. The experimental treatments consisted of different replacement levels of SBM by urea (DM basis): 0% replacement (R-0%); 54% replacement (R-54%); 78% replacement (R-78%); 100% replacement (R-100%). Diets were formulated according to the BR-CORTE system to provide approximately 130 g CP/kg DM. The diets consisted of 20% corn silage and 80% ground corn-based concentrate containing SBM and/or urea+ammonium sulfate, mineral mix, and virginiamycin. Each experimental period was 21 d, with 14 d adaptation, and 4 d of total feces and urine collection. Data were analyzed using the MIXED procedure in SAS and statistical significance was declared at P < 0.05. Dietary treatment did not influence (P > 0.05) OM and CP intake. Apparent total-tract OM and CP digestibility were not influenced (P > 0.05) by dietary treatment. Daily total urinary and fecal N were not influenced (P > 0.05) by dietary treatment. Dietary treatment did not influence (P > 0.05) N retention. Therefore, these data suggest that SBM may be partially or totally replaced by urea as the dietary N source without affecting feed intake, apparent total-tract digestibility, and N balance in Nellore × Red Angus crossbreed young bulls fed a high concentrate diet.