Growth response to escape protein and forage intake by growing cattle grazing cornstalks

Two trials were conducted to study the protein requirements of growing cattle grazing cornstalks. Diet composition and forage intake were determined at different periods during the grazing season. Residue intake and dietary CP content decreased (P less than .05) .079 kg and .044 percentage units per day of grazing, respectively. In vitro DM disappearance of the roughage fraction of the diet remained high early in the grazing period when husk availability was high, then declined in a curvilinear pattern. Calves required time to learn to find and consume the residual grain. During 54 d of grazing in Trial 1, calves supplemented with 409 g CP gained .105 kg/d more than those supplemented with 213 g CP. Maximal daily gain (.308 kg) in Trial 2 was obtained with 163 g/d of ruminal escape protein. Growing cattle grazing cornstalks responded to protein supplementation at levels above current National Research Council recommendations for 250-kg calves gaining .3 kg/d.