Van Koevering M T, Gill D R, Owens F N, Dolezal H G, Strasia C A
Department of Animal Science, Oklahoma State University, Stillwater 74078-0425.
J Anim Sci. 1995 Jan;73(1):21-8. doi: 10.2527/1995.73121x.
Two hundred fifty-six British and Continental crossbred yearling steers (329 kg initially) were fed to study the effect of time on feed on live performance, carcass characteristics, tissue composition, and steak tenderness. Steers were divided into four slaughter groups and fed for either 105, 119, 133, or 147 d. Daily gains (carcass weight-adjusted basis) increased in a quadratic manner (P < .05; maximum at 119 d), whereas feed intake tended to increase linearly (P < .08) as cattle were fed longer. Feed conversion (carcass weight-adjusted basis) for steers fed 119 d was superior to that of steers fed for 147 d. Carcass weight, s.c. fat thickness, kidney, pelvic, and heart fat, overall carcass maturity, and yield grade increased linearly (P < .01) with time on feed. Marbling score and the percentage of cattle grading U.S. Choice increased (linearly; P < .01) with time on feed but at a decreasing rate (quadratic; P < .05). Cholesterol and total lipid concentrations in longissimus muscle increased linearly (P < .01) as time on feed increased, whereas the percentage of protein and moisture tended to decrease linearly (P < .10 and P < .01). Tenderness of ribeye steaks tended to increase linearly (P < .07) with time on feed, primarily due to a linear decrease (P < .03) in the percentage of steaks considered tough (shear force above 4.50 kg). Performance and carcass characteristics indicate that a feedlot finishing period of 119 to 133 d is ideal for British Continental crossbred yearling steers (329 kg).
选用256头英国和欧洲大陆杂交一岁公牛（初始体重329千克）进行饲养试验，以研究育肥时间对其生长性能、胴体特性、组织成分和牛排嫩度的影响。将公牛分为四个屠宰组，分别育肥105、119、133或147天。日增重（以胴体重校正为基础）呈二次曲线增加（P < 0.05；119天时达到最大值），而随着育肥时间延长，采食量呈线性增加趋势（P < 0.08）。育肥119天的公牛的饲料转化率（以胴体重校正为基础）优于育肥147天的公牛。胴体重、皮下脂肪厚度、肾、盆腔和心脏脂肪、胴体整体成熟度和产肉等级随育肥时间呈线性增加（P < 0.01）。大理石花纹评分和美国精选级牛肉的比例随育肥时间呈线性增加（P < 0.01），但增加速率呈下降趋势（二次曲线；P < 0.05）。随着育肥时间增加，背最长肌中的胆固醇和总脂质浓度呈线性增加（P < 0.01），而蛋白质和水分的比例呈线性下降趋势（P < 0.10和P < 0.01）。肋眼牛排的嫩度随育肥时间呈线性增加趋势（P < 0.07），主要原因是被认为较硬的牛排比例（剪切力高于4.50千克）呈线性下降（P < 0.03）。生长性能和胴体特性表明，对于体重329千克的英国和欧洲大陆杂交一岁公牛，育肥期为119至133天较为理想。
