Kriese L A, Bertrand J K, Benyshek L L
Anim. and Dairy Sci. Dept., University of Georgia, Athens 30602.
J Anim Sci. 1991 Feb;69(2):478-89. doi: 10.2527/1991.692478x.
Field data records on 10,511 Hereford and 2,522 Brangus bulls between 330 and 430 d of age were analyzed to find age of calf and age of dam adjustment factors for yearling scrotal circumference. Age of calf adjustment factors were .024 cm/d for Hereford bulls and .041 cm/d for Brangus bulls. Sons of Hereford dams were adjusted to a 6- to 8-yr dam age basis by adding .7, .3, .2, .2 or .3 cm for dams 2, 3, 4, 5 or 8 or more years old, respectively. Age of dam adjustment factors for Brangus bulls were .8, .4, .3 and .2 for dams 2, 3, 4 or 8 or more years old, respectively. Variance and covariance components for yearling scrotal circumference and several growth traits were estimated within breed using multiple-trait models and pseudo expectations involving the solutions and the right-hand sides of the mixed-model equations. Additive heritability estimates for yearling scrotal circumference of .53 and .16 were found for Hereford and Brangus bulls, respectively. Maternal heritability estimates of .12 and .10 were found for Hereford and Brangus bulls, respectively. Genetic correlations between yearling scrotal circumference and other growth traits were positive for both sets of data indicating that selection for yearling scrotal circumference should not adversely affect other growth traits in either breed. Environmental correlation estimates between yearling scrotal circumference and adjusted birth weight and between yearling scrotal circumference and adjusted 205-d weight and adjusted 365-d height were positive and moderate in magnitude for both breeds.
分析了10511头赫里福德公牛和2522头勃莱格斯公牛在330至430日龄之间的现场数据记录，以确定一岁龄阴囊周长的犊牛年龄和母牛年龄调整因子。赫里福德公牛的犊牛年龄调整因子为0.024厘米/天，勃莱格斯公牛为0.041厘米/天。对于赫里福德母牛的儿子，根据母牛年龄在6至8岁的基础上进行调整，2岁、3岁、4岁、5岁或8岁及以上的母牛分别增加0.7厘米、0.3厘米、0.2厘米、0.2厘米或0.3厘米。勃莱格斯公牛的母牛年龄调整因子，2岁、3岁、4岁或8岁及以上的母牛分别为0.8、0.4、0.3和0.2。使用多性状模型和涉及混合模型方程解和右侧的伪期望，在品种内估计一岁龄阴囊周长和几个生长性状的方差和协方差分量。赫里福德和勃莱格斯公牛一岁龄阴囊周长的加性遗传力估计值分别为0.53和0.16。赫里福德和勃莱格斯公牛的母体遗传力估计值分别为0.12和0.10。两组数据中一岁龄阴囊周长与其他生长性状之间的遗传相关性均为正，这表明选择一岁龄阴囊周长不会对任何一个品种的其他生长性状产生不利影响。两个品种一岁龄阴囊周长与调整后出生体重之间、一岁龄阴囊周长与调整后205日龄体重和调整后365日龄身高之间的环境相关性估计值均为正且幅度适中。
