Intake and Digestion of Low-Quality Meadow Hay by Steers and Performance of Cows on Native Range When Fed Protein Supplements Containing Various Levels of Corn

摘要

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 \u3c .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corn and ear corn plus protein gained more (P \u3c .001) weight during calving and summer grazing (after supplement was withdrawn) than protein-supplemented cows. Reproductive performance was not affected (P \u3e .705) by treatments.