Roehe R, Kennedy B W
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
J Anim Sci. 1995 Oct;73(10):2959-70. doi: 10.2527/1995.73102959x.
Genetic variances and covariances for the number of pigs born in total (NOBT), the number of pigs born alive (NOBA), and the number of weaned pigs (NOW) were estimated by REML under an animal model. Data on 30,357 and 42,041 litters born between 1977 and 1992 from Yorkshire and Landrace sows, respectively, were obtained from the Quebec Record of Performance sow productivity program. Data of the first four parities of litter size were used for four different analyses under an animal model: univariate analyses with direct genetic effects only, univariate analyses with maternal and direct genetic effects , seri0s of bivariate analyses with each parity treated as a different trait, and a series of bivariate analyses between NOBT, NOBA, and NOW within each parity. Heritabilities of different parities from univariate analyses under a direct genetic effects model ranged from .10 to .15, .09 to .14, and .06 to .08 for NOBT, NOBA, and NOW, respectively. Estimates of direct heritability from bivariate analyses between parties were consistent with estimates from univariate analyses in Landrace but not in Yorkshire. Genetic correlations between first and secondary parity in Yorkshire were .59, .49, and .17 for NOBT, NOBA, and NOW, and in Landrace were .90, .93, and .81, respectively. Influence of maternal effects on moderate correlations between first and secondary parity in Yorkshire was suggested. Genetic correlations averaged over all parities between NOBA and NOBT or NOW were .97 and .65 in Yorkshire and .97 and .82 in Landrace. A multiple-trait animal model with parities treated as different traits was recommended.
在动物模型下，采用限制最大似然法（REML）估计了总产仔数（NOBT）、活产仔数（NOBA）和断奶仔猪数（NOW）的遗传方差和协方差。分别从魁北克母猪生产性能记录计划中获取了1977年至1992年间约克夏母猪和长白母猪产仔的30357窝和42041窝数据。在动物模型下，使用头四胎产仔数数据进行了四种不同分析：仅含直接遗传效应的单变量分析、含母体和直接遗传效应的单变量分析、将每一胎次视为不同性状的一系列双变量分析，以及每一胎次内NOBT、NOBA和NOW之间的一系列双变量分析。在直接遗传效应模型下，单变量分析中不同胎次的遗传力，NOBT范围为0.10至0.15，NOBA为0.09至0.14，NOW为0.06至0.08。不同胎次间双变量分析的直接遗传力估计值在长白猪中与单变量分析结果一致，但在约克夏猪中不一致。约克夏猪第一胎与第二胎之间，NOBT、NOBA和NOW的遗传相关性分别为0.59、0.49和0.17，长白猪中分别为0.90、0.93和0.81。这表明母体效应影响了约克夏猪第一胎与第二胎之间的中等相关性。约克夏猪中，所有胎次平均的NOBA与NOBT或NOW之间的遗传相关性分别为0.97和0.65，长白猪中分别为0.97和0.82。推荐使用将胎次视为不同性状的多性状动物模型。
