Department of Animal Science, University of Nebraska, Lincoln 68583-0908, USA.
J Anim Sci. 2010 Jun;88(6):1967-72. doi: 10.2527/jas.2009-2391. Epub 2010 Feb 26.
Records of individual feed intake (FI) and BW gain (GN) were obtained from the Germ Plasm Evaluation (GPE) program at US Meat Animal Research Center (USMARC). Animals were randomly assigned to pens. Only pens with 6 to 9 steers (n = 289) were used for this study (data set 1). Variance components and genetic parameters were estimated using data set 1. Estimated genetic values (EGV) for FI were calculated by 5 methods using single and 2-trait analyses: 1) individual FI and individual GN, 2) individual FI alone, 3) 2-trait with individual GN but with FI missing, 4) individual GN and pen total FI, and 5) pen total FI alone. Analyses were repeated but with some of the same records assigned artificially to 36 pens of 5 and 4 paternal half sibs per pen (data sets 2 and 3). Models included year as a fixed factor and birth and weaning weights, age on test, and days fed as covariates. Estimates of heritability were 0.42 +/- 0.16 and 0.34 +/- 0.17 for FI and GN. The estimate of the genetic correlation was 0.57 +/- 0.23. Empirical responses to selection were calculated as the average EGV for the top and bottom 10% based on rank for each method but with EGV from method 1 substituted for the EGV on which ranking was based. With data set 1, rank correlations between EGV from method 1 and EGV from methods 2, 3, 4, and 5 were 0.99, 0.53, 0.32, and 0.15, respectively. Empirical responses relative to method 1 agreed with the rank correlations. Accuracy of EGV for method 4 (0.44) was greater than for method 3 (0.35) and for method 5 (0.29). Accuracies for methods 4 and 5 were greater than indicated by empirical responses and correlations with EGV from method 1. Comparisons of the 5 methods were similar for data sets 2 and 3. With data set 2, rank correlations between EGV from method 1 and EGV from methods 3, 4, and 5 were 0.47, 0.64, and 0.62. Average accuracies of 56, 75, and 75% relative to method 1 (0.67) generally agreed with the empirical responses to selection. As expected, accuracy using pen total FI and GN to obtain EGV for FI was greater than using GN alone. With data set 1, empirical response to selection with method 4 was one-third of that for method 1, although average accuracy was 65% of that for method 1. With assignment of 5 paternal half sibs to artificial pens, using pen total FI and individual GN was about 81% as effective for selection as using individual FI and GN to obtain EGV for FI and was substantially more effective than use of GN alone.
个体采食量（FI）和体重增加（GN）记录来自美国肉类动物研究中心（USMARC）的种质评估（GPE）计划。动物被随机分配到围栏中。只有有 6 到 9 头育肥牛（n=289）的围栏被用于本研究（数据集 1）。使用数据集 1 估计方差分量和遗传参数。使用 5 种方法，通过单性状和双性状分析计算 FI 的估计遗传值（EGV）：1）个体 FI 和个体 GN，2）个体 FI 单独，3）个体 GN 但 FI 缺失的双性状，4）个体 GN 和栏总 FI，5）栏总 FI 单独。重复了分析，但将一些相同的记录人为地分配给了 36 个 5 和 4 个父半同胞/每栏（数据集 2 和 3）。模型包括年份作为固定因素，出生和断奶体重、测试时的年龄和饲养天数作为协变量。FI 和 GN 的遗传力估计值分别为 0.42 +/- 0.16 和 0.34 +/- 0.17。遗传相关性的估计值为 0.57 +/- 0.23。根据每种方法的排名，以排名前 10%和后 10%的个体的平均 EGV 来计算选择的经验响应，但用方法 1 的 EGV 替代排名的 EGV。对于数据集 1，方法 1 的 EGV 与方法 2、3、4 和 5 的 EGV 之间的秩相关系数分别为 0.99、0.53、0.32 和 0.15。基于方法 1 的 EGV 与方法 1 和方法 2、3、4 和 5 的 EGV 之间的秩相关系数分别为 0.99、0.53、0.32 和 0.15。基于方法 1 的 EGV 之间的经验响应与秩相关系数一致。方法 4（0.44）的准确性大于方法 3（0.35）和方法 5（0.29）。方法 4 和 5 的准确性大于经验响应和与方法 1 的 EGV 的相关性所表明的准确性。对于数据集 2，方法 1 的 EGV 与方法 3、4 和 5 的 EGV 之间的秩相关系数分别为 0.47、0.64 和 0.62。相对于方法 1（0.67）的 56%、75%和 75%的平均准确性通常与选择的经验响应一致。正如预期的那样，使用栏总 FI 和 GN 获得 FI 的 EGV 的准确性大于单独使用 GN。对于数据集 1，方法 4 的经验选择响应是方法 1 的三分之一，尽管平均准确性是方法 1 的 65%。在分配 5 个父半同胞到人工围栏中时，使用栏总 FI 和个体 GN 进行选择与使用个体 FI 和 GN 获得 FI 的 EGV 一样有效，并且比单独使用 GN 更有效。
