DelCurto T, Cochran R C, Corah L R, Beharka A A, Vanzant E S, Johnson D E
Kansas State University, Manhattan 66506.
J Anim Sci. 1990 Feb;68(2):532-42. doi: 10.2527/1990.682532x.
Two experiments were conducted to evaluate the influence of supplemental protein concentration on the intake and utilization of dormant range forage by beef cattle. In Exp. 1,97 pregnant Hereford x Angus cows (avg wt = 454 kg) were assigned randomly to three isocaloric treatment supplements: 1) low protein (LP), 13% CP; 2) moderate protein (MP), 25% CP; and 3) high protein (HP), 39% CP. In Exp. 2, 15 ruminally and 12 esophageally cannulated steers (avg wt = 319 and 355 kg, respectively) were assigned randomly to LP, MP and HP treatments and were used in a 22-d winter grazing trial to evaluate forage intake and utilization characteristics. In Exp. 1, cow body condition (BC) and BW changes responded in linear (P less than .01) and quadratic (P less than .01) fashions to increasing protein concentration, with MP and HP displaying the least BC and BW loss from trial initiation (d 1) through d 84. From d 84 to calving (avg calving date = d 120), only the HP supplement continued to be effective in minimizing BC loss (P less than .01). Calf birth weight tended (P = .17) to increase in a linear fashion to increasing supplemental protein concentration, but calf ADG and cow reproductive efficiency were unaffected (P greater than .10). In Exp. 2, forage OM intake responded in a quadratic fashion (P less than .10), with the MP treatment having the highest NDF digestibility and ruminal OM fill. In conclusion, beef cow BC and BW losses during the winter grazing period were minimized with increasing supplemental CP concentration. Intake and utilization of dormant forage by steers were improved with moderate (26%) levels of CP in the supplement.
进行了两项试验，以评估补充蛋白质浓度对肉牛采食和利用休眠期牧场草料的影响。在试验1中，97头怀孕的赫里福德×安格斯母牛（平均体重=454千克）被随机分配到三种等热量的处理性补充饲料中：1）低蛋白（LP），粗蛋白含量13%；2）中蛋白（MP），粗蛋白含量25%；3）高蛋白（HP），粗蛋白含量39%。在试验2中，15头安装了瘤胃瘘管和12头安装了食管瘘管的阉牛（平均体重分别为319千克和355千克）被随机分配到LP、MP和HP处理组，并用于一项为期22天的冬季放牧试验，以评估草料采食和利用特性。在试验1中，母牛的体况（BC）和体重变化对蛋白质浓度增加呈线性（P<0.01）和二次曲线（P<0.01）反应，从中期（第1天）到第84天，MP和HP组的BC和体重损失最小。从第84天到产犊（平均产犊日期=d 120），只有HP补充饲料在最小化BC损失方面继续有效（P<0.01）。犊牛出生体重倾向于（P=0.17）随补充蛋白质浓度增加呈线性增加，但犊牛平均日增重和母牛繁殖效率未受影响（P>0.10）。在试验2中，草料有机物摄入量呈二次曲线反应（P<0.10），MP处理组的中性洗涤纤维消化率和瘤胃有机物充盈度最高。总之，随着补充粗蛋白浓度的增加，冬季放牧期肉牛的体况和体重损失最小化。阉牛对休眠草料的采食和利用在补充饲料中粗蛋白含量为中等水平（26%）时得到改善。
