Mashiloane M L, Nephawe K A, Maiwashe A, Norris D, Ngambi J W
Department of Animal Production, University of Limpopo, Private Bag X 1106, Sovenga 0727, South Africa.
Trop Anim Health Prod. 2009 Dec;41(8):1723-30. doi: 10.1007/s11250-009-9371-2. Epub 2009 May 31.
Data on South African Angus cattle consisting of 45 259 records on weaning weight (WWT), 4 360 records on average daily gain from on-farm test (ADG-D) and 1 118 from centralized test (ADG-C) were analyzed to evaluate the effect of pre-weaning selection on estimates of genetic parameters and subsequent estimated breeding values (EBV) for post-weaning average daily gain. (Co)variance components and genetic parameters for weaning weight (WWT), ADG-C and ADG-D were estimated by REML procedures fitting three different animal models. Model 1 was a univariate model of WWT, ADG-C or ADG-D and did not account for the effect of pre-weaning selection on post-weaning ADG. Model 2 was a two-trait model of WWT and either ADG-C or ADG-D. Model 3 was a multi-trait animal model including WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39 +/- 0.080, 0.42 +/- 0.060 and 0.44 +/- 0.010 from Model 1, 2 and 3 respectively. Corresponding estimates for ADG-D were 0.18 +/- 0.020, 0.19 +/- 0.020 and 0.21 +/- 0.020 respectively. Rank correlations based on EBVs for ADG-C for all bulls were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model 3, and Model 2 vs. Model 3, respectively and they indicated a possible re-ranking of bulls when including or excluding a correlated pre-weaning trait. Rank correlations for ADG-D also followed a similar trend. Inclusion of pre-weaning information in genetic analysis for post-weaning average daily gain is necessary to account for selection at weaning.
对南非安格斯牛的数据进行了分析，这些数据包括45259条断奶体重（WWT）记录、4360条农场测试平均日增重（ADG-D）记录和1118条集中测试平均日增重（ADG-C）记录，以评估断奶前选择对遗传参数估计以及断奶后平均日增重的后续估计育种值（EBV）的影响。通过拟合三种不同动物模型的REML程序，估计了断奶体重（WWT）、ADG-C和ADG-D的（协）方差成分和遗传参数。模型1是WWT、ADG-C或ADG-D的单变量模型，未考虑断奶前选择对断奶后ADG的影响。模型2是WWT与ADG-C或ADG-D的双性状模型。模型3是包括WWT、ADG-C和ADG-D的多性状动物模型。模型1、2和3对ADG-C的遗传力估计分别为0.39±0.080、0.42±0.060和0.44±0.010。ADG-D的相应估计分别为0.18±0.020、0.19±0.020和0.21±0.020。基于所有公牛ADG-C的EBV的秩相关系数，模型1与模型2、模型1与模型3、模型2与模型3分别为0.92、0.83和0.94，这表明在纳入或排除相关的断奶前性状时，公牛可能会重新排名。ADG-D的秩相关也遵循类似趋势。在断奶后平均日增重的遗传分析中纳入断奶前信息对于考虑断奶时的选择是必要的。
