摘要
Different methods of estimating weight gain were compared for accuracy and utility, using the amount of error variation from fitting the residual feed intake (RFI) model. Data were collected on 1481 cattle of temperate and tropically adapted breeds, feedlot-finished for the domestic (liveweight 400 kg), Korean (520 kg), or Japanese (steers only; 600 kg) markets. Cattle were tested in 36 groups over 4 years. The aim was to estimate weight gain over the period feed intake was measured, which was at least 49 days and averaged 63 days, including time for animals to adapt to the automatic feeding system. The different estimates were derived from linear and quadratic regressions of weight over time fitted to: F1) all weighings in the feedlot and F2) all weighings in the feedlot excluding atypical records in the first few weeks following feedlot entry. More complex linear and quadratic models were also fitted to weighings when feed intake was being measured, using the amount of feed eaten on the day of weighing, and previous days, to adjust for gut fill. Finally, a random regression model including general trends in the growth of each animal and short term measurement error was fitted to dataset F2 to estimate weight gain for the period feed intake was measured.
The RFI equation: feed intake=intercept(s)+βw*mean(weight0.73)+βg*weight gain+error (i.e. RFI) was fitted using the different weight gain estimates. Based on mean squared errors from fitting this equation, longer measurement periods generally resulted in more accurate estimates of weight gain. The increased accuracy from using all weight measurements in the feedlot outweighed the loss from not measuring over the desired time interval—i.e. the period for which feed intake was measured.
摘要译文
使用来自拟合残余采食量（RFI）模型的误差变化量，比较估计体重增加的不同方法的准确性和效用。数据收集于1481头温带和热带适应品种的牛，饲养场为国内（活体重400公斤），韩国（520公斤）或日本（仅限阉牛; 600公斤）市场。牛在4年内在36组中进行了测试。目的是估计在采食期间的体重增加，测量至少49天，平均63天，包括动物适应自动喂养系统的时间。不同的估算值来自于重量随时间变化的线性和二次回归：F1）饲养场中的所有称重和F2）饲养场中的所有称量，不包括饲养场进入后最初几周的非典型记录。当测量采食量时，使用在称重当天和前几天食用的饲料量来调整肠道填充量时，还采用更复杂的线性和二次模型进行称重。最后，将包括每只动物生长的一般趋势和短期测量误差的随机回归模型拟合到数据集F2，以估计期间采食量的体重增加。 RFI方程：采食量=截距（s）+βw*平均值（重量 0.73 ）+βg*重量增加+误差（即使用不同的体重增加估计来拟合RFI）。基于拟合该等式的均方误差，较长的测量周期通常导致更准确的体重增加估计。在饲养场中使用所有重量测量值的准确度增加超过了在所需时间间隔内未测量的损失 - 即。测量采食量的时间。
D.L.Robinson;. Assessing the accuracy of modelling weight gain of cattle using feed efficiency data[J]. Livestock Production Science, 2005,95(3): 187-200