genetic parameters for body weight and laying traits in mazandaran native breeder hens

heritability, environmentaland genetic correlations between body weight at hatch (bw0), eight (bw8) and twelve (bw12) weeksof age, body weight at sexual maturity (bwm), age at sexual maturity (afe),the weight of the first egg laid by the hen (ewm), the mean egg weight from 28 to 32 wks (ew28-32) and egg numbers (ens) were estimated by the restricted maximum likelihood method under an animal model. data were from six generations (generation ten to fifteen) of hens kept at the mazandaran breeding center of iran. heritability estimates for bw0, bw8, bw12, bwm, afe, ewm, ew28-32 and ens were 0.134, 0.235, 0.296, 0.247, 0.344, 0.125, 0.240 and 0.156, respectively. genetic correlations between pairs of body weight measures were moderate with a range from 0.17 to 0.43. generally, correlations of body weight traits with afe were weak. genetic correlation between bw8 and afe was low, but favorable (-0.17). egg numbers has unfavorable genetic correlation with bwm (-0.47). however, egg weight traits had favorable genetic correlation with body weight traits, except bw0, which was almost equal to zero. age at first egg had negative genetic correlation with egg numbers, but positive correlations with egg weight traits. the absolute value of environmental correlations between traits varied from 0.00 to 0.39. the strongest environmental correlation was found between afe and ewm. there was moderate and positive environmental correlation between bw8 and bw12as well asbetween bw12 and bwm. the results showed that there are considerable genetic variations in important traits of mazandaran native hens, and that selection on bw8, ens and ewm, which are the most economicallyimportant traits in this breed, could be effective.