Meissner H H, Smuts M, Coertze R J
Department of Animal and Wildlife Sciences, University of Pretoria, Republic of South Africa.
J Anim Sci. 1995 Apr;73(4):931-6. doi: 10.2527/1995.734931x.
Most prediction equations of feedlot performance cover average daily gains (ADG) below 1.5 kg/d. The question is whether these equations would be accurate for higher ADG. Medium-to-large-framed weanling and yearling steer calves were fed individually using a transponder-electronic gate system in three feedlot trials and fed in groups in two trials. Average daily gain ranged from .9 to 2.1 kg. Steers were implanted, fed to the same degree of finish, and slaughtered to obtain dressing percentage and cold carcass weight. Initial carcass weights were estimated from initial slaughter groups. Dietary ME concentration (i.e., 10.5, 11.5, 12.0, and 12.5 MJ ME/kg of DM, where 1 Mcal = 4.184 MJ), initial weight, dry matter intake (DMI), and days fed could explain 57% of the variation in ADG. The partial contribution of DMI to the total variation was only 5.2%, confirming the low correlation between DMI and ADG in feedlot trials. The correlation between metabolizable energy intake (MEI) and MEI/ADG also was low, but 80% of the variation in MEI/ADG was accounted for by the variation in ADG. Intake patterns, regardless of dietary energy concentration, indicate that ADG increased with DMI only when ADG was below 1.5 kg/d. Therefore, current prediction equations apparently overpredict ME requirements for fast-growing feedlot steers. Optimal performance occurred at a ME concentration of 12.0 MJ/kg of DM rather than 12.5 MJ/kg of DM. Dressing percentage and carcass gain increased as dietary energy concentration and ADG increased, and current prediction equations should predict that of fast-growing feedlot steers equally well.
大多数育肥性能预测方程所涵盖的平均日增重（ADG）低于1.5千克/天。问题在于这些方程对于更高的ADG是否准确。在三项育肥试验中，使用应答器 - 电子门系统对中大型体格的断奶犊牛和周岁阉公牛犊进行个体饲养，在两项试验中进行群体饲养。平均日增重范围为0.9至2.1千克。给阉公牛植入激素，饲养至相同的育肥程度，然后屠宰以获得屠宰率和冷胴体重。初始胴体重根据初始屠宰组进行估算。日粮代谢能浓度（即10.5、11.5、12.0和12.5兆焦代谢能/千克干物质，其中1兆卡 = 4.184兆焦）、初始体重、干物质摄入量（DMI）和饲养天数可解释ADG变异的57%。DMI对总变异的部分贡献仅为5.2%，这证实了在育肥试验中DMI与ADG之间的低相关性。代谢能摄入量（MEI）与MEI/ADG之间的相关性也较低，但MEI/ADG变异的80%可由ADG的变异来解释。无论日粮能量浓度如何，采食模式表明，只有当ADG低于1.5千克/天时，ADG才会随DMI增加。因此，当前的预测方程显然高估了快速生长育肥牛的代谢能需求。最佳性能出现在代谢能浓度为12.0兆焦/千克干物质时，而非12.5兆焦/千克干物质时。随着日粮能量浓度和ADG的增加，屠宰率和胴体增重增加，当前的预测方程应该同样能够很好地预测快速生长育肥牛的情况。
