Campos M S, Wilcox C J, Becerril C M, Diz A
Dairy Science Department, University of Florida, Gainesville 32611.
J Dairy Sci. 1994 Mar;77(3):867-73. doi: 10.3168/jds.S0022-0302(94)77021-1.
Records of yield and reproduction from 4293 Holstein and 2143 Jersey first lactation cows from eight Holstein and six Jersey herds were utilized to evaluate genetic parameters for Florida, a subtropical environment. Statistical analyses were by derivative-free REML with the animal model. Genetic variances were based on variation in estimated breeding values of individual cows. Heritabilities were .27 to .43 for yields (6 estimates), .38 to .51 for constituent percentages (4 estimates), and .025 to .056 for reproduction (6 estimates), which were similar to estimates for temperature areas from similar procedures. Also, correlations of breeding values between yields were high and between yields and reproduction were low and generally antagonistic. Correlated responses in calving interval from selection for yield, with selection intensities of 1.0 to 1.5, would be expected to lead to increases of 1.0 to 5.2 d per generation (12 estimates). Thus, estimates of genetic parameters and correlated responses in this subtropical environment did not differ appreciably from those that occur in temperate dairy areas.
利用来自8个荷斯坦牛群和6个泽西牛群的4293头荷斯坦初产奶牛和2143头泽西初产奶牛的产量和繁殖记录，对亚热带环境下的佛罗里达州的遗传参数进行评估。统计分析采用无导数约束最大似然法和动物模型。遗传方差基于个体奶牛估计育种值的变异。产量的遗传力为0.27至0.43（6个估计值），成分百分比的遗传力为0.38至0.51（4个估计值），繁殖的遗传力为0.025至0.056（6个估计值），这些与采用类似方法对温带地区的估计值相似。此外，产量之间育种值的相关性较高，产量与繁殖之间的相关性较低，且通常呈拮抗关系。在选择强度为1.0至1.5的情况下，因选择产量而导致的产犊间隔的相关反应预计每代增加1.0至5.2天（12个估计值）。因此，在这种亚热带环境下的遗传参数估计值和相关反应与温带奶牛养殖地区的估计值没有明显差异。
