ABSTRACT

1. Genetic (co)variances and parameters between body weights (BW) across the growth trajectory were estimated using a univariate random regression (RR) animal model. The effect of growth rates (GH) on age at first egg (AFE) and egg weight at first egg (EWFE) were explored using a series of univariate and bivariate analyses.

2. Body weights were taken from Thai native chickens at hatch day to 168 days of age. The model included interactions between age with hatch nested within year and sex as fixed effects, and random effects of direct additive genetic, direct permanent environmental, maternal genetic and maternal permanent environmental effects. All random effects were fitted as regressions to animals’ age via quadratic Legendre polynomials and fitting six classes of residual variances was identified as an optimal variance structure to estimate parameters.

3. Genetic and phenotypic variances for BW increased with increasing age. Estimated heritabilities for direct additive (h² _a) and maternal genetic (h² _m) effects on BW traits ranged from 0.34 to 0.54, and 0.04 to 0.06, respectively. Estimated variance ratios for direct (c² _ape) and maternal permanent environmental (c² _mpe) effects ranged from 0.19 to 0.48 and 0.10 to 0.12, respectively. Estimated correlations between weights at different ages were high for all random effects.

4. Estimated h² _a for six GH traits ranged from 0.06 to 0.28, while for AFE and EWFE these were 0.24 and 0.16, respectively. Estimated h² _m and c² _mpe were low for GH. Estimated genetic correlations between GH and AFE ranged from −0.22 to 0.02 and, between GH and EWFE, ranged from −0.05 to 0.40. These estimates suggested that selecting high GH chickens at 28 days of age can be expected to reduce AFE and to increase EWFE.

摘要

1.使用单变量随机回归（RR）动物模型估算了整个生长轨迹上的遗传（协）方差和体重（BW）之间的参数。使用一系列单变量和双变量分析，探讨了生长速率（GH）对第一个蛋龄（AFE）和第一个蛋重（EWFE）的影响。

2.体重取自孵化日至168日龄的泰国土鸡。该模型包括年龄内嵌套的年龄与性别之间的相互作用以及固定效应，以及直接加成遗传，直接永久环境，母体遗传和母体永久环境效应的随机效应。通过二次Legendre多项式将所有随机效应拟合为动物年龄的回归，并拟合出六类残差方差作为估计参数的最佳方差结构。

3.随着年龄的增长，体重的遗传和表型差异增加。对BW性状的直接加性（h ² _a）和母体遗传（h ²  _m）影响的估计遗传力分别为0.34至0.54和0.04至0.06。直接（c ² _ape）效应和产妇永久环境（c ²  _mpe）效应的估计方差比分别为0.19至0.48和0.10至0.12。对于所有随机效应，不同年龄体重之间的估计相关性都很高。

4.六个GH性状的h ² _a估计值为0.06至0.28，而AFE和EWFE的h ² _a分别为0.24和0.16。GH的估计h ²  _m和c ²  _mpe低。GH和AFE之间的估计遗传相关性介于-0.22至0.02之间，GH和EWFE之间的估计遗传相关性介于-0.05至0.40之间。这些估计表明，选择28日龄的高GH鸡可以减少AFE并增加EWFE。