Roasted, steeped soybeans for growing steers fed alfalfa–grass silage

Abstract

A 56-d growth trial was conducted to evaluate performance and plasma amino acid (AA) responses of 63 Charolais-crossed steer calves fed alfalfa–grass silage diets. The basal diet was supplemented with either high-moisture corn (control), roasted, flaked, steeped (1 h) soybeans or a 60:40 (dry basis) mixture of corn gluten and blood meal (CG–BM). All diets were balanced for net energy, while the steeped soybeans and CG–BM diets were balanced for rumen-undegradable protein (RUP). Dry matter intake was similar across diets (2.39% of BW). Weight gains were higher (P < 0.01) for the steers fed with CG–BM (12.6%) and soybean (6.9%) supplemented rations than control steers. Digestibilities of neutral and acid detergent fibre were not adversely affected by roasted, steeped soybeans. Plasma glucose was lower (P < 0.05) and plasma urea was higher (P < 0.05) in the soybean- and CG–BM-supplemented steers than in control steers. Supplementation with steeped soybeans or CG–BM increased (P < 0.001) total plasma essential AA, branched-chain AA (BCAA) and BCAA/glycine ratio and lowered the total nonessential AA (NEAA) to essential AA (EAA) ratio. Plasma AA parameters were directly related to the rumen undegradability of the protein supplements. A lower plasma NEAA/EAA ratio indicated improved protein nutrition. These results showed that roasted, steeped soybeans delivered needed protein to the small intestine of rapidly growing steers fed alfalfa–grass silage. Key words: Roasting, steeped, soybeans, protein