Date of this Version
Two trials were conducted to evaluate the effects of corn in protein supplements fed to cattle receiving low-quality forages. In Trial 1, four ruminally cannulated steers (avg BW 550 kg) and four intact steers (avg BW 270 kg) were used in a replicated latin square to determine intake and digestibility of a low-quality meadow hay (4.3% CP) when fed no supplement (NS), 1.12 g CP/kg BW (PS), 1.12 g CP/kg BW with corn supplying 1.98 g starch/kg BW (PLC) or 1.12 g CP/kg BW with corn supplying 3.96 g starch/kg BW (PHC). Hay DM1 decreased (P = .001) and total diet DM1 increased (P = .001) quadratically as supplemental corn increased. Diet DM digestibility increased (P = .004) and forage DM and hemicellulose digestibility decreased (P ≤ .018) quadratically as level of corn in the diet increased. In Trial 2, 135 cows received either ear corn (1.16 kg TDN and 127 g CP∙hd-1∙d-1), ear corn plus protein (1.16 kg TDN and 290 g CP∙hd-1∙d-1) or protein (.72 kg TDN and 290 g CP∙hd-1∙d-1) while grazing native Sandhills winter range for 112 d and while receiving hay (10% CP) during the following 60-d calving period. Cows that received ear corn lost (P < .001) more weight than cows fed ear corn plus protein supplement, which lost more weight than cows fed only protein supplement (-54, -18 and 6 kg, respectively) during the 112-d winter grazing period. Cows that received ear corn and ear corn plus protein gained more (P < .001) weight during calving and summer grazing (after supplement was withdrawn) than protein-supplemented cows. Reproductive performance was not affected (P > .705) by treatments.