Goodling R C, Shook G E, Weigel K A, Zwald N R
Department of Dairy Science, University of Wisconsin, Madison, 53706, USA.
J Dairy Sci. 2005 Jun;88(6):2217-25. doi: 10.3168/jds.S0022-0302(05)72897-6.
Genetic evaluation and selection is one strategy for improving female reproductive performance. Many producers use synchronization of ovulation or estrus to manage reproduction. The objective of this study was to examine the effects of reproductive synchronization on genetic parameter estimates of days to first breeding (DFB), days open (DO), and pregnancy rate at 120 d postpartum (PR120). Data were collected from 64 producers participating in an artificial insemination progeny testing program and using Dairy Comp 305 herd management software to record reproductive treatments and events. Data included 18,359 records for DFB and 16,379 records for DO and PR120. Synchronization was classified by breeding codes at time of insemination. The traits DFB and DO were analyzed using a linear model with age at calving, herd-year-season, and parity as fixed effects and sire and residual as random effects. For PR120, a threshold sire model was used with fixed effects as in the DFB and DO models. Three models were applied to the complete data sets of all traits; a base model with no synchronization effect, an expanded model with a fixed synchronization effect, and an interaction model with a random sire by herd management interaction. Herd management categories were based on an individual herd's use of synchronization protocols. Also, data subsets were analyzed separately based on cow synchronization treatment and herd management categories. Synchronized records for DFB had on average 40% higher sire variance and 60% lower residual variance than nonsynchronized records. Heritability for DFB ranged from 0.01 to 0.09. Sire variance was 40% lower for DO and 25% lower for PR120 in first synchronized records than either later-synchronized or nonsynchronized records. Residual variances for DO varied by 3% among cow treatment categories and 14% for herd management categories. Heritabilities ranged from 0.03 to 0.07 for DO and 0.10 to 0.26 for PR120. Including a fixed effect for synchronization in the DO model reduced sire variance by 33% and residual variance by 10%. Sire by herd management interactions were less than 2% of the total variance for all traits. Accounting for synchronization, especially for DFB, may improve accuracy of genetic parameter estimates and animal evaluations.
遗传评估与选择是提高母牛繁殖性能的一种策略。许多养殖者采用排卵或发情同步化来管理繁殖。本研究的目的是检验繁殖同步化对首次配种天数（DFB）、空怀天数（DO）以及产后120天妊娠率（PR120）的遗传参数估计值的影响。数据收集自64个参与人工授精后代测试项目并使用Dairy Comp 305牛群管理软件记录繁殖处理和事件的养殖者。数据包括18359条DFB记录以及16379条DO和PR120记录。同步化根据授精时的配种代码进行分类。对DFB和DO性状，使用一个以产犊年龄、牛群-年份-季节和胎次为固定效应、 sire和残差为随机效应的线性模型进行分析。对于PR120，使用一个阈值 sire模型，其固定效应与DFB和DO模型中的相同。三个模型应用于所有性状的完整数据集；一个无同步化效应的基础模型、一个有固定同步化效应的扩展模型以及一个有随机sire与牛群管理相互作用的交互模型。牛群管理类别基于单个牛群对同步化方案的使用情况。此外，根据母牛同步化处理和牛群管理类别分别对数据子集进行分析。DFB的同步化记录相比非同步化记录， sire方差平均高40%，残差方差低60%。DFB的遗传力范围为0.01至0.09。首次同步化记录中，DO的 sire方差比后期同步化或非同步化记录低40%，PR120的 sire方差低25%。DO的残差方差在母牛处理类别间相差3%，在牛群管理类别间相差14%。DO的遗传力范围为0.03至0.07，PR120的遗传力范围为0.10至0.26。在DO模型中纳入同步化的固定效应使 sire方差降低33%，残差方差降低10%。sire与牛群管理的相互作用占所有性状总方差的比例不到2%。考虑同步化，尤其是对于DFB，可能会提高遗传参数估计和动物评估的准确性。
