Research Note: Genetic parameters for egg production and clutch-related traits in indigenous Beijing-You chickens

Egg products from indigenous chickens have growing market shares as consumers are pursuing differentiation in egg consumption. The genetic improvement in egg production performance of those breeds is crucial for increasing the economic profit. This study aimed to estimate genetic parameters for egg production and clutch-related traits in indigenous Beijing-You chickens for understanding the genetic architecture and exploring proper biological traits for selection. Data on traits including age at first egg (AFE), egg number (EN), average clutch length (ACL), maximum clutch length (MCL), number of clutches (NC) and pauses (NP), and average pause length (APL) were collected from 4 generations of purebred Beijing-You chickens based on the 43-wk and 66-wk of individual egg production record. The heritabilities, genetic and phenotypic correlations were analyzed by the DMU software with the restricted maximum likelihood method in a multivariate animal model. The results showed that the AFE of Beijing-You chickens was 174.45 d of age, and its heritability was as high as 0.62. The heritability was 0.26 for EN43 and 0.18 for EN66. The clutch traits including ACL, MCL, NC, and NP were moderate to high heritable (h² = 0.15-0.39), but APL was very low heritable (h² = 0.05). Genetic correlations were high between AFE and EN (r_{G(AFE, EN43)} = -0.79, r_{G(AFE, EN66)} = -0.39), whereas low between AFE and ACL (r_{G(AFE, ACL43)} = -0.08, r_{G(AFE, ACL66)} = 0.01) and MCL (r_{G(AFE, MCL)} = -0.07). EN had higher correlations with ACL (r_{G(EN43, ACL43)} = 0.59, r_{G(EN66, ACL66)} = 0.40) than that with MCL (r_{G(EN43, MCL43)} = 0.56, r_{G(EN66, MCL66)} = 0.32). The heritability for ACL43 (h² = 0.38) was higher than that for MCL43 (h² = 0.33). ACL43 had a positive correlation with EN66 (r_{G(ACL43, EN66)} = 0.62). These results indicated that the egg production of whole laying period could be improved by early selection for AFE and ACL at the same time in Beijing-You chickens.