DeNise S K, Torabi M
University of Arizona, Tucson 85721.
J Anim Sci. 1989 Oct;67(10):2619-26. doi: 10.2527/jas1989.67102619x.
Postweaning growth data, collected from a Hereford herd located in the Southwest, were used to estimate genetic parameters for weights and gains. The herd was maintained on unsupplemented range forage, and average weight losses from weaning to yearling age were 9% for bulls and 12% for heifers. Data were grouped into years with poor and good environments based on contemporary group means for gain from 8 to 12 mo. Postweaning growth data (12- and 20-mo weights, 8- to 12-mo gain and 12- to 20-mo gain) were analyzed by least squares methods with a model that included year of birth, sire within year of birth, age of dam and a covariate of age for 12- and 20-mo weights. Heritability estimates of 12- and 20-mo weights for bulls were .58 +/- .15 and .55 +/- .22 in good environments vs .32 +/- .11 and 1.09 +/- .15 in poor environments; for heifers these estimates were .19 +/- .08 and .35 +/- .12 in good environments vs .38 +/- .07 and .47 +/- .09 in poor environments. Heritability estimates of 8- to 12-mo and 12- to 20-mo gain for bulls were .32 +/- .14 and .51 +/- .24 in good environments vs .16 +/- .11 and .09 +/- .14 in poor environments; for heifers these estimates were .21 +/- .08 and .14 +/- .10 in good environments vs .10 +/- .06 and .44 +/- .10 in poor environments. Genetic correlations among the preweaning traits of birth and weaning weight and postweaning weight traits were positive and of a moderate to large magnitude, with the exception of birth and 12-mo weight in a poor environment (-.06 +/- .49). Genetic correlations between 8- to 12-mo gain and birth weight in poor environment and weaning weight in all environments were negative (range from -.06 +/- .33 to -.53 +/- .41). Genetic correlations among 12- and 20-mo weights were large and positive in all environments. Relationships among gains were more variable.
从位于美国西南部的一个赫里福德牛群收集的断奶后生长数据，用于估计体重和增重的遗传参数。该牛群依靠未补充的天然牧草维持生存，公牛从断奶到一岁龄的平均体重损失为9%，母牛为12%。根据8至12月龄增重的同期组均值，将数据分为环境较差和较好的年份。断奶后生长数据（12月龄和20月龄体重、8至12月龄增重以及12至20月龄增重）采用最小二乘法进行分析，模型包括出生年份、出生年份内的父亲、母亲年龄以及12月龄和20月龄体重的年龄协变量。在良好环境中，公牛12月龄和20月龄体重的遗传力估计值分别为0.58±0.15和0.55±0.22，而在较差环境中分别为0.32±0.11和1.09±0.15；对于母牛，在良好环境中这些估计值分别为0.19±0.08和0.35±0.12，在较差环境中分别为0.38±0.07和0.47±0.09。在良好环境中，公牛8至12月龄和12至20月龄增重的遗传力估计值分别为0.32±0.14和0.51±0.24，在较差环境中分别为0.16±0.11和0.09±0.14；对于母牛，在良好环境中这些估计值分别为0.21±0.08和0.14±0.10，在较差环境中分别为0.10±0.06和0.44±0.10。断奶前出生重和断奶重性状与断奶后体重性状之间的遗传相关性为正，且幅度适中至较大，但在较差环境中出生重与12月龄体重之间的相关性除外（-0.06±0.49）。在较差环境中，8至12月龄增重与出生重之间以及在所有环境中与断奶重之间的遗传相关性为负（范围从-0.06±0.33至-0.53±0.41）。在所有环境中，12月龄和20月龄体重之间的遗传相关性大且为正。增重之间的关系更具变异性。
