Barley- versus protein-supplemented corn-based diets for feedlot cattle evaluated using the NRC and CNCPS beef models

Abstract

A study was conducted to evaluate the effects of supplementing a corn-based finishing diet [10.0% crude protein (CP), 6.2% degradable intake protein (DIP), dry matter basis, no protein supplementation] with DIP in the form of urea (13.0% CP, 9.1% DIP) or canola meal and urea (12.8% CP, 8.6% DIP) on dry matter intake (DMI) and average daily gain (ADG). Animal performances were compared with those obtained by feeding a barley-based diet (13.9% CP, 9.6% DIP). Crossbred beef steers (398 ± 28 kg) were allocated to 24 pens and six pens were assigned to each diet. There were no differences (P > 0.05) in DMI and ADG between cattle fed the barley diet and those fed the corn diets supplemented to provide a concentration of DIP similar to that supplied by the barley diet. However, ADG was 10% lower and DMI was 8% lower for cattle fed the corn diet with no protein supplementation (P < 0.05). The NRC and CNCPS models predicted the substantially lower gain of cattle fed the corn diet with no protein supplementation, but underestimated the improvement in performance when the corn diet was supplemented with urea or canola meal and urea to supply the requirement for DIP. Key words: Feedlot cattle, protein, corn, barley, growth, models