ROASTED, STEEPED SOYBEANS FOR GROWING STEERS FED ALFALFA GRASS-SILAGE

A 56-d growth trial was conducted to evaluate performance and plasma a mino acid (AA) responses of 63 Charolais-crossed steer calves fed alfa lfa-grass silage diets. The basal diet was supplemented with either hi gh-moisture com (control), roasted, flaked, steeped (1 h) soybeans or a 60:40 (dry basis) mixture of com 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 matte r intake was similar across diets (2.39% of BW). Weight gains were hig her (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, stee ped 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 i n control steers. Supplementation with steeped soybeans or CG-BM incre ased (P < 0.001) total plasma essential AA, branched-chain AA (BCAA) a nd BCAA/glycine ratio and lowered the total nonessential AA (NEAA) to essential AA (EAA) ratio. Plasma AA parameters were directly related t o the rumen undegradability of the protein supplements. A lower plasma NEAA/EAA ratio indicated improved protein nutrition. These results sh owed that roasted, steeped soy