Urea Levels and Supplemental Energy Sources in Sugarcane Diets

Abstract

Two experiments, each involving a digestion-N balance trial and a feedlot trial, determined the replacement value of urea-corn meal (UC) for cottonseed meal (CSM) and the value of molasses in sugarcane diets. Steers fed 70% sugarcane-30% concentrate diets with 0, 28 or 56% of the dietary N as urea had a slight reduction (P<.28) in dry matter (DM) intake and an increase (P<.01) in crude protein digestibility as dietary urea increased. Urea level did not affect the digestibility of other dietary components. Urea N appeared to be utilized less efficiently than CSM N. In the feedlot, steers were fed 71% sugarcane-29% concentrate diets with 0, 25 or 50% of the dietary N as urea during a 93-d growing phase, then 39.5% sugarcane-60.5% concentrate diets with 0, 20 or 40% of the dietary N as urea, respectively, during a 63-d finishing phase. Growing steers fed urea gained slower (P<.01), consumed less DM and required more DM/kg of gain (P<.05). Dietary urea level did not affect gain, DM intake or DM utilization during finishing, nor did it affect carcass quality. Steers fed 70% sugarcane-30% concentrate diets, with urea and CSM as N supplements and molasses and corn as energy supplements to the high-urea diet, had higher DM digestibility (P<.01) for the urea-molasses (UM) supplemented diet than for the CSM diet. Digestibilities of all components of the UM and UC diets were similar. Retention of N was similar for steers fed the UC and CSM diets, but both groups retained more N than steers fed the UM diet. In the feedlot, steers fed the UM diet gained slower (P<.01) with lower efficiency than steers fed the CSM or UC diets. Performance of steers fed CSM or UC diets was similar. This study showed that urea was inferior to CSM as a crude protein source in sugarcane diets, especially when molasses was used as an energy supplement.