Department of Animal Sciences, The Ohio State University, Columbus 43210.
J Anim Sci. 2011 Dec;89(12):3924-34. doi: 10.2527/jas.2011-4125. Epub 2011 Jul 15.
A divergent selection experiment for serum IGF-I concentration was established in 1989 at the Eastern Agricultural Research Station located in Belle Valley, Ohio. One hundred spring-calving (50 high line and 50 low line) and 100 fall-calving (50 high line and 50 low line) cows with unknown IGF-I concentrations were randomly assigned to the 2 divergent selection lines. Results of this study included 2,507 calves from the 1989 through 2005 calf crops. (Co)variance components were estimated for direct and maternal additive genetic effects using an animal model and multiple-trait, derivative-free, REML (MTDFREML) computer programs. Estimated breeding values were also obtained and regressed on years to estimate direct and correlated responses to divergent selection for serum IGF-I concentration. Estimates of direct heritability for growth traits from a single trait model were moderate and ranged from 0.33 ± 0.06 for birth weight to 0.42 ± 0.06 for preweaning BW gain. Heritability estimates for direct effects were 0.44 ± 0.07, 0.43 ± 0.07, 0.35 ± 0.06, and 0.48 ± 0.07 for IGF-I concentration at d 28, 42, and 56 of the 140-d postweaning period, and for mean IGF-I concentration, respectively. Maternal heritability and the proportion of phenotypic variance due to permanent environment effect of dam were ≤0.25 for growth traits and IGF-I concentrations. Cattle in the high line had significantly (P < 0.001) greater direct effects of mean IGF-I concentration than those in low line (high line: 66.92 ± 4.40 ng/mL vs. low line: -40.82 ± 5.18 ng/mL) in 2005. Direct responses per year for mean IGF were 5.18 ng/mL in the high line and -3.76 ng/mL in the low line. The regression of direct effects of preweaning BW gain on year were not significantly different from zero in either the high or low line. However, genetic trends were negative and significant for birth weight and postweaning BW gain in the high line and were positive and significant in the low line. Results demonstrated that divergent selection for serum IGF-I concentration in beef cattle will change the genetic potential for IGF-I concentration and that selection for lesser IGF-I concentration will result in increased birth weights and postweaning BW gains.
1989 年，在美国俄亥俄州贝尔谷的东部农业研究站建立了一个针对血清 IGF-I 浓度的分歧选择实验。100 头春季产犊（50 头高线和 50 头低线）和 100 头秋季产犊（50 头高线和 50 头低线）奶牛，其 IGF-I 浓度未知，被随机分配到 2 个分歧选择线。本研究的结果包括 1989 年至 2005 年牛犊的 2507 头小牛。使用动物模型和多性状、无导数、REML（MTDFREML）计算机程序，估计了直接和母体加性遗传效应的协方差分量。还获得了估计的育种值，并对年份进行回归，以估计血清 IGF-I 浓度的分歧选择的直接和相关反应。单性状模型中生长性状的直接遗传力估计值适中，范围从出生体重的 0.33±0.06 到断奶前 BW 增益的 0.42±0.06。直接效应的遗传力估计值分别为 0.44±0.07、0.43±0.07、0.35±0.06 和 0.48±0.07，分别为 IGF-I 浓度在断奶后 140 天的第 28、42 和 56 天和平均 IGF-I 浓度。生长性状和 IGF-I 浓度的母体遗传力和母体永久性环境效应的表型方差比例均≤0.25。高线牛的平均 IGF-I 浓度的直接效应显著（P<0.001）大于低线牛（高线：66.92±4.40ng/mL vs. 低线：-40.82±5.18ng/mL）2005 年。高线和低线的平均 IGF 每年的直接反应分别为 5.18ng/mL 和-3.76ng/mL。高线和低线的前断奶 BW 增益的直接效应回归均不显著为零。然而，高线的出生体重和断奶后 BW 增益的遗传趋势为负且显著，而低线的遗传趋势为正且显著。结果表明，对肉牛血清 IGF-I 浓度进行分歧选择将改变 IGF-I 浓度的遗传潜力，选择较低的 IGF-I 浓度将导致出生体重和断奶后 BW 增益增加。
