Roehe R
Institute of Animal Breeding and Husbandry, Christian-Albrechts-University of Kiel, Germany.
J Anim Sci. 1999 Feb;77(2):330-43. doi: 10.2527/1999.772330x.
Genetic association between individual birth weight (IBW) and litter birth weight (LBW) was analyzed on records of 14,950 individual pigs born alive between 1988 and 1994 at the pig breeding farm of the University of Kiel. Dams were from three purebred lines (German Landrace, German Edelschwein, and Large White) and their crosses. Phenotypically, preweaning mortality of pigs decreased substantially from 40% for pigs with < or = 1 kg weight to less than 7% for pigs with > 1.6 kg. For these low to high birth weight categories, preweaning growth (d 21 of age) and early postweaning growth (weaning to 25 kg) increased by more than 28 and 8% per day, respectively. Bayesian analysis was performed based on direct-maternal effects models for IBW and multiple-trait direct effects models for number of pigs born in total (NOBT) and alive (NOBA) and LBW. Bayesian posterior means for direct and maternal heritability and litter proportion of variance in IBW were .09, .26, and .18, respectively. After adjustment for NOBT, these changed to .08, .22, and .09, respectively. Adjustment for NOBT reduced the direct and maternal genetic correlation from -.41 to -.22. For these direct-maternal correlations, the 95% highest posterior density intervals were -.75 to -.07, and -.58 to .17 before and after adjustment for NOBT. Adjustment for NOBT was found to be necessary to obtain unbiased estimates of genetic effects for IBW. The relationship between IBW and NOBT, and thus the adjustment, was linear with a decrease in IBW of 44 g per additionally born pig. For litter traits, direct heritabilities were .10, .08, and .08 for NOBT, NOBA, and LBW, respectively. After adjustment of LBW for NOBA the heritability changed to .43. Expected variance components for LBW derived from estimates of IBW revealed that genetic and environmental covariances between full-sibs and variation in litter size resulted in the large deviation of maternal heritability for IBW and its equivalent estimate for LBW. These covariances among full-sibs could not be estimated if only LBW were recorded. Therefore, selection for increased IBW is recommended, with the opportunity to improve both direct and maternal genetic effects of birth weight of pigs and, thus, their vitality and pre- and postnatal growth.
利用基尔大学养猪场1988年至1994年间出生的14950头存活仔猪的记录，分析了个体出生体重（IBW）与窝产仔重（LBW）之间的遗传关联。母猪来自三个纯种品系（德国长白猪、德国埃德尔施温猪和大白猪）及其杂交后代。从表型上看，仔猪断奶前死亡率从体重≤1kg的仔猪的40%大幅下降到体重>1.6kg的仔猪的不到7%。对于这些低出生体重到高出生体重类别，断奶前生长（21日龄）和断奶后早期生长（断奶至25kg）分别每天增加超过28%和8%。基于IBW的直接-母体效应模型以及总产仔数（NOBT）、存活仔数（NOBA）和LBW的多性状直接效应模型进行贝叶斯分析。IBW的直接遗传力、母体遗传力和窝产仔数方差比例的贝叶斯后验均值分别为0.09、0.26和0.18。在对NOBT进行调整后，这些值分别变为0.08、0.22和0.09。对NOBT进行调整后，直接遗传相关和母体遗传相关从-0.41降至-0.22。对于这些直接-母体相关性，在对NOBT进行调整前后，95%最高后验密度区间分别为-0.75至-0.07和-0.58至0.17。发现对NOBT进行调整对于获得IBW遗传效应的无偏估计是必要的。IBW与NOBT之间的关系以及因此的调整是线性的，每多出生一头仔猪，IBW下降44g。对于窝产仔数性状，NOBT、NOBA和LBW的直接遗传力分别为0.10、0.08和0.08。在对LBW进行NOBA调整后，遗传力变为0.43。从IBW估计值得出的LBW的预期方差分量表明，全同胞之间的遗传和环境协方差以及窝产仔数的变化导致了IBW的母体遗传力与其LBW等效估计值之间的巨大偏差。如果仅记录LBW，则无法估计全同胞之间的这些协方差。因此，建议选择增加IBW，以提高仔猪出生体重的直接和母体遗传效应，从而提高其活力以及产前和产后生长。
