estimation of genetic parameters for productive and reproductive traits in esfahan native chickens

the main aim of this research was to estimate the genetic and phenotypic parameters for productive and reproductive traits of esfahan native chickens. traits included body weights at hatch (bw1), 8 weeks of age (bw8), 12 weeks of age (bw12), and at sexual maturity (wsm)], age at sex maturity (asm), egg number (en), average egg weight (aew) in the first 12 weeks of production, and egg production intensity (eint). data were collected over 13 generations (during 1998 to 2011) at the breeding center of esfahan native chickens in iran. genetic parameters were estimated by a (bi)-univariate animal model using the restricted maximum likelihood (reml) procedure. heritability estimates for body weight at different ages varied from 0.14±0.01 to 0.42±0.01. estimated heritability for reproductive traits ranged from 0.12±0.01 for eint to 0.36±0.01 for aew. estimates of heritability values were moderate but bw1 and aew showed higher heritability values. genetic correlation among body weight traits varied from 0.20±0.03 to 0.82±0.02. fairly small negative genetic correlation between body weight traits and egg traits (en and eint) was small (in the range of -0.22±0.05 to -0.03±0.03), while they showed positive and moderate genetic correlation with the average egg weight, ranging from 0.11±0.04 to 0.39±0.02.  there was a low negative genetic correlation (-0.09±0.02) between egg number and egg weight. therefore, during simultaneous selection for growth and egg production, probable reduction in egg production due to low reduction in egg number may be compared by increases in egg weight.