Noguera J L, Varona L, Babot D, Estany J
Area de Producció Animal, Centre UdL-IRTA, Lleida, Spain.
J Anim Sci. 2002 Oct;80(10):2548-55. doi: 10.2527/2002.80102548x.
Litter size and production trait responses to experimental selection for increased litter size in a Landrace pig population are reported. The numbers of sows and litters available for the first cycle of selection were 3,034 and 961, respectively. Selection was carried out using a BLUP repeatability animal model for number of piglets born alive (NBA). The experiment included one selection and one control line, each with three nonoverlapping generations. The selection line (H) consisted of the 160 sows with the highest breeding values and one boar from each of 25 full-sib families with the highest breeding values. The control line (C) consisted of 160 sows and 25 boars randomly chosen. The two subsequent generations in each line were obtained by random selection. A Bayesian analysis of genetic response using a multivariate model was carried out by Gibbs sampler. Marginal posterior distributions were obtained for direct response in NBA, and for correlated response in weight (WT), and backfat thickness (BT) at 175 d of age. The posterior means and posterior standard deviation (PSD) for direct genetic response of NBA ranged from 0.32 (PSD 0.08) in the first parity to 0.64 (PSD 0.08) in the fourth. The posterior means for correlated genetic response in WT and BT were -0.66 kg (PSD 0.36) and 0.20 mm (PSD 0.10), respectively. For WT and BT, the 95% highest posterior density regions (HPD) contain zero-correlated genetic response. Marginal posterior distributions of selection differentials were investigated. The posterior means for standardized selection differentials for NBA in different parities ranged from 0.70 (PSD 0.12) to 0.94 (PSD 0.06) in females for line H, from 0.22 (PSD 0.19) to 0.34 (PSD 0.10) in males for line H, and from 0.08 (PSD 0.08) to 0.13 (PSD 0.07) in females for line C. All available males were used in line C. Results from this experiment showed that selection for increased litter size is effective. Responses to selection were heterogeneous across parities, suggesting that litter size in each parity may have a different genetic background. No correlated genetic response to growth and backfat thickness was observed.
本文报道了长白猪群体中窝产仔数及生产性状对增加窝产仔数的实验性选择的反应。第一轮选择中可用的母猪和窝数分别为3034头和961窝。使用最佳线性无偏预测（BLUP）重复性动物模型对产活仔数（NBA）进行选择。该实验包括一个选择系和一个对照系，每个系有三个不重叠的世代。选择系（H）由160头繁殖价值最高的母猪和来自25个全同胞家系中繁殖价值最高的每家一头公猪组成。对照系（C）由随机选择的160头母猪和25头公猪组成。每个系的后续两代通过随机选择获得。使用吉布斯抽样器对遗传反应进行了多变量模型的贝叶斯分析。获得了产活仔数直接反应、175日龄体重（WT）和背膘厚（BT）相关反应的边际后验分布。产活仔数直接遗传反应的后验均值和后验标准差（PSD）范围从第一胎的0.32（PSD 0.08）到第四胎的0.64（PSD 0.08）。体重和背膘厚相关遗传反应的后验均值分别为-0.66千克（PSD 0.36）和0.20毫米（PSD 0.10）。对于体重和背膘厚，95%最高后验密度区域（HPD）包含零相关遗传反应。研究了选择差的边际后验分布。选择系H中不同胎次产活仔数标准化选择差的后验均值，在雌性中范围从0.70（PSD 0.12）到0.94（PSD 0.06），在雄性中范围从0.22（PSD 0.19）到0.34（PSD 0.10）；对照系C中雌性的范围从0.08（PSD 0.08）到0.13（PSD 0.07）。对照系C使用了所有可用的雄性。本实验结果表明，增加窝产仔数的选择是有效的。各胎次对选择的反应是异质的，这表明每一胎次的窝产仔数可能具有不同的遗传背景。未观察到对生长和背膘厚的相关遗传反应。
