Genetic analysis of growth efficiency-related traits in Mazandaran native chickens

•The influence of maternal effects on offspring phenotype was significant.•Genetic correlations between direct and maternal genetic were negative.•Estimates of heritability were low for relative growth rates.•Heritability Estimates were low to moderate for growth efficiencies and Kleiber ratios. The aim of this study was to investigate the genetic and phenotypic aspects of growth efficiency-related traits in Mazandaran native chickens. For this purpose, phenotypic and pedigree data of 21 generations were obtained from Mazandaran native chicken breeding center. Studied traits included Kleiber ratio (KR), relative growth rate (RGR) and growth efficiency (EF) at different growth phases from hatch to 8 weeks of age (1-8), hatch to 12 weeks of age (1-12), 8 weeks to 12 weeks of age (8-12), hatch to sex maturity (1-SM), 8 weeks of age to sex maturity (8-SM) and 12 weeks of age to sex maturity (12-SM). Genetic parameters and (Co) variance components were estimated by Restricted Maximum Likelihood (REML) procedure under six different univariate animal models using WOMBAT software with and without considering the maternal effects. Based on the results of the best model, determined by the Akaike Information Criterion (AIC), the estimates of direct heritability ranged from 0.05 (EF8-12) to 0.32 (EF12-SM) for growth efficiency, from 0.06 (KR8-12) to 0.37 (KR8 -SM) for Kleiber ratios and from 0.06 (RGR8-12) to 0.16 (RGR1-12) for relative growth rates. Maternal heritability ranged from 0.03 (EF8-12, EF1-8) to 0.08 (EF1-SM) for growth efficiency, from 0.006 (KR8-12) to 0.097 (KR1-SM) for Kleiber ratios and form 0.03 (RGR8-12) to 0.14 (RGR1-12) for relative growth rates. Negative genetic correlations between direct and maternal additive genetic effects were estimated for all studied traits. In conclusion, significant maternal effects indicated that these effects should be considered in genetic evaluation of traits.