Hermas S A, Young C W, Rust J W
J Dairy Sci. 1987 Jun;70(6):1252-7. doi: 10.3168/jds.S0022-0302(87)80138-8.
Data were first lactation production and reproduction records initiated from 1958 to 1981 in two experiment station Guernsey herds. Heritability estimates using paternal half sib groups were .24 +/- .12 for milk yield, .27 +/- .12 for fat yield, and .77 +/- .15 for fat percentage. Heritability estimates for reproductive traits ranged from .01 to .04 for number of services, service period, conception rate, and days open, but were higher for days in milk at first breeding (.12) and age at first calving (.13). Except for age at first calving, coefficients of additive genetic variation were larger for reproductive traits than for productive traits. Genetic correlations between measures of production and reproduction were moderate to large and antagonistic, except that the relationship between production and age at first calving was favorable. Breeding value estimates for milk yield and reproduction were negatively correlated for sires with above average breeding values for milk yield. Huge phenotypic variances for reproductive traits masked substantial additive genetic variation for these traits. When all things are considered it seems unwise to ignore reproductive performance in selection programs for dairy cattle.
数据来自1958年至1981年在两个实验站的根西牛群的首次泌乳生产和繁殖记录。利用父系半同胞组估计的遗传力，产奶量为0.24±0.12，产脂量为0.27±0.12，乳脂率为0.77±0.15。繁殖性状的遗传力估计值，配种次数、配种期、受胎率和空怀天数为0.01至0.04，但首次配种时的泌乳天数（0.12）和初产年龄（0.13）的遗传力较高。除初产年龄外，繁殖性状的加性遗传变异系数大于生产性状。生产和繁殖指标之间的遗传相关性中等至较大且呈拮抗关系，不过产奶量与初产年龄之间的关系是有利的。对于产奶量育种值高于平均水平的公牛，产奶量和繁殖的育种值估计呈负相关。繁殖性状的巨大表型变异掩盖了这些性状大量的加性遗传变异。综合考虑所有因素，在奶牛选择计划中忽视繁殖性能似乎是不明智的。
