The performance of the two‐trait animal model that regards the first parity and later parities as two different traits in estimating genetic parameters for number of born alive (NBA) was examined using real and simulated data. Genetic parameters for NBA were estimated in purebred Landrace and Large White pigs using a single‐trait repeatability model (Model 1) that regards all parities as the same trait and a two‐trait animal model (Model 2) that regards the first and the later parities as different traits. For Model 2, the permanent environmental effect was fitted to only the records of the later parities. Heritability for NBA estimated using Model 1 was 0.12 for Landrace and 0.11 for Large White. Estimated heritability for NBA of the first parity and the later parities was 0.21 and 0.16, respectively, for Landrace; 0.18 and 0.16, respectively, for Large White obtained using Model 2, and higher than those in both breeds obtained using Model 1. Further results based on data simulated using the Monte Carlo method suggest that estimated additive genetic variance could be more biased using Model 2 than Model 1.

中文翻译：

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两种模型的比较，用于估计猪出生活数的遗传参数。

使用真实数据和模拟数据检验了双性状动物模型的性能，该模型将第一胎和后来的胎次视为两个不同的性状，用于估计活产数 (NBA) 的遗传参数。NBA 的遗传参数是在纯种长白猪和大白猪中使用单性状重复性模型（模型 1）和双性状动物模型（模型 2）进行估计的，该模型将所有胎次视为相同性状平价作为不同的特征。对于模型 2，永久环境影响仅适用于后来的奇偶校验记录。使用模型 1 估计的 NBA 遗传力长白为 0.12，大白为 0.11。对于 Landrace，第一胎和第二胎 NBA 的估计遗传力分别为 0.21 和 0.16；分别为 0.18 和 0.16，