摘要
To evaluate feed efficiency using residual feed intake (RFI), it is necessary to measure and record daily feed intake for each animal. This can be accomplished by housing them in individual pens or by using sophisticated electronic feeders in group pens. All the available options are very expensive and very laborious; therefore, several researchers have developed methods to predict individual DMI of cattle fed in group pens. Three intake models were tested with a data set of 60 Angus × Hereford steers fed a corn-based finishing diet in both group and individual pens. After the first 60 d (period 1) of the study, animals were switched from group to individual pens, and then vice versa for another 60 d (period 2); thus, the entire feeding trial was 120 d long. No difference was observed in DMI between periods for steers fed individually (period 1 = 10.9 kg/d and period 2 = 11.2 kg/d, P = 0.44), but a difference was observed in group pens (period 1 = 12.7 kg/d and period 2 = 10.9 kg/d, P < 0.01). In addition, no difference (P ≥ 0.15) was observed in carcass characteristics, such as HCW, dressing percentage, quality grade, LM area, KPH percentage, yield grade, or backfat between RFI groups (low, medium, and high). Average daily gain and G:F were not different between RFI groups within each period (P ≥ 0.06), but there were period differences (P < 0.001). Models 1 and 2 were based on growth, carcass composition, and nutrient requirements, whereas model 3 was based on the heterogeneity of pen intakes when cattle were rotated through the pens on a daily basis. Models 1 and 2 were forced through the mean observed DMI, so the mean bias was zero, but they were not precise, with a slope bias greater than 50%. Model 3 showed low accuracy (mean bias = 20%), but it was precise, with a slope bias of 21%. Because RFI is the error of the DMI equation, any inaccuracy when estimating intake will lead to a bias in the prediction of RFI. In conclusion, these models could be used to predict mean DMI, but they were not adequate for estimating RFI.
摘要译文
为了使用残余采食量（RFI）评估饲料效率，有必要测量和记录每只动物的每日采食量。这可以通过将它们放在单独的笔中或通过在组笔中使用复杂的电子馈线来实现。所有可用的选项都非常昂贵且非常费力;因此，一些研究人员开发了一些方法来预测喂养在组围栏中的牛的个体DMI。使用60只Angus×Hereford阉牛的数据集测试了三种摄入模型，在组和个体围栏中饲喂基于玉米的整理饮食。在研究的第一个60天（期间1）之后，将动物从组切换到个体围栏，然后反之亦然另外60天（期间2）;因此，整个喂养试验是120天长。单独饲喂的阉牛期间DMI没有差异（1期= 10.9 kg / d，2期= 11.2 kg / d，P = 0.44），但在组围栏中观察到差异（1期= 12.7 kg / d）期间2 = 10.9 kg / d，P <0.01）。此外，在胴体特征中没有观察到差异（P≥0.15），例如HCW，修整百分比，质量等级，LM面积，KPH百分比，产量等级或RFI组（低，中和高）之间的背back。每个时期内RFI组的平均日增重和G：F无差异（P≥0.06），但存在时间差异（P <0.001）。模型1和2基于生长，胴体组成和营养需求，而模型3基于当牛每天旋转通过笔时笔插入的异质性。模型1和2被迫通过平均观察到的DMI，因此平均偏差为零，但它们不精确，斜率偏差大于50％。模型3显示低精度（平均偏差= 20％），但精确，斜率偏差为21％。由于RFI是DMI方程的误差，因此在估算摄入量时的任何不准确性都会导致RFI预测的偏差。总之，这些模型可用于预测平均DMI，但它们不足以估计RFI。