Direct and maternal genetic effects for traits at the first egg in Rugao yellow chickens

Objective The aims of this study were to evaluate direct and maternal genetic effects for traits at the first egg of Rugao yellow chickens with animal models, and to estimate the genetic parameters for these traits.

Method Reproduction data, including data for 10 454 individual animals and 31 362 reproduction records, of Rugao yellow chickens from 2009 to 2012 were collected. Four animal models with and without maternal effects were used to estimate the genetic parameters. Phenotypic variance of reproduction traits was partitioned using average information restricted maximum likelihood (AIREML) method with WOMBAT software. The models were evaluated with the likelihood ratio test. Univariate models were used to estimate heritabilities, and multivariate models were used to analyze genetic and phenotypic correlations.

Result Maternal environment had significant influence on age at the first egg (AFE), for which the optimum model was model Ⅱ and the heritability was 0.28±0.02. Maternal genetic effects had significant influence on egg mass at the first egg (EM1), for which the optimum model was model Ⅲ, the direct heritability was 0.23±0.02 and the maternal genetic heritability was 0.03±0.01. Both maternal environment and maternal genetic effects had significant influence on body mass at the first egg (BM1), for which the optimum model was model Ⅳ, the heritability was 0.34±0.03 and the maternal genetic heritability was 0.04±0.01. There were negative correlations between the direct and maternal genetic effects for EM1 and BM1. The genetic correlation coefficients between AFE and BM1, AFE and EM1, and EM1 and BM1 were 0.36±0.07, 0.33±0.07, and 0.65±0.05, respectively.

Conclusion The traits at the first egg of Rugao yellow chickens are influenced by maternal effects, and are lowly heritable.