Bullock K D, Bertrand J K, Benyshek L L
Department of Animal Science, University of Georgia, Athens 30602.
J Anim Sci. 1993 Jul;71(7):1737-41. doi: 10.2527/1993.7171737x.
Variances and covariances were estimated for birth weight (BWT), weaning weight (WW), yearling gain (YG), yearling weight (YW), yearling height (YH), relative growth from birth to weaning (RGW) and weaning to yearling (RGY), and mature weight (MW). Field records on 572,446 Polled Hereford cattle were analyzed. Because multiple dam weights were collected on a cow the MW used in the analysis was calculated using a nonlinear regression correction factor computed by fitting a quadratic with a plateau to the data. If the cow had an observation(s) beyond the inflection point (IP), the closest weight to that point was used. If the cow only had observation(s) before the IP the closest weight to that point was nonlinearly adjusted to the plateau. The IP for this data set was 1,506 d and the plateau was 554.7 kg. Heritabilities and genetic and environmental correlations were calculated from the appropriate (co)variances and phenotypic correlations were computed. Heritability estimates for BWT, WW, YG, YW, YH, RGW, RGY, and MW were .49, .24, .23, .30, .59, .24, .15, and .52, respectively. Genetic correlations between MW with BWT, WW, YG, YW, YH, RGW, and RGY were .64, .80, .76, .89, .73, -.29, and .35, respectively, environmental correlations were .15, .43, .05, .40, 1.03, .32, and -.10, respectively, and phenotypic correlations were .33, .32, .28, .46, .70, .00, and .07, respectively.
对出生体重（BWT）、断奶体重（WW）、周岁增重（YG）、周岁体重（YW）、周岁身高（YH）、出生至断奶的相对生长率（RGW）、断奶至周岁的相对生长率（RGY）以及成熟体重（MW）的方差和协方差进行了估计。对572,446头无角海福特牛的田间记录进行了分析。由于在一头母牛上收集了多个母畜体重数据，分析中使用的MW是通过对数据拟合一个带有平稳期的二次曲线计算出的非线性回归校正因子来计算的。如果母牛有超过拐点（IP）的观测值，则使用最接近该点的体重。如果母牛只有在IP之前的观测值，则将最接近该点的体重非线性调整至平稳期。该数据集的IP为1,506天，平稳期为554.7千克。根据适当的（协）方差计算遗传力以及遗传和环境相关性，并计算表型相关性。BWT、WW、YG、YW、YH、RGW、RGY和MW的遗传力估计值分别为0.49、0.24、0.23、0.30、0.59、0.24、0.15和0.52。MW与BWT、WW、YG、YW、YH、RGW和RGY之间的遗传相关性分别为0.64、0.80、0.76、0.89、0.73、 -0.29和0.35，环境相关性分别为0.15、0.43、0.05、0.40、1.03、0.32和 -0.10，表型相关性分别为0.33、0.32、0.28、0.46、0.70、0.00和0.07。
