study of growth pattern in parental lines of arian commercial broiler chicken

in order to investigate the growth curve of broiler chickens at line level, respectively 154 and 144 birds from two paternal lines a and b of a commercial broiler line were used. line a were selected several generations for low feed conversion rate and line b were selected several generation for high body weight. body weight was measured at 1, 4, 7, 10, 14, 17, 21, 28, 35, 42, 49 and 54 days of age and the growth curve were fitted by gompertz model. moreover, feed conversion rate were evaluated just for 20% of birds within 23 and 54 day of age. at the end of experiment, all birds were slaughtered and some carcass traits like breast weight, liver and abdominal fat were assayed. the results of current study showed that mature index and the age at inflection point in male birds of line b were higher than that in line a. female broilers in line b showed higher hatch weight, mature index and age at the inflection point than that in line a. the hatch weight, mature index and age at the inflection point were similar between male and female birds in both paterntal lines. liver weight, abdominal fat and feed conversion rate among male birds in paterntal lines were no significant, but the difference in breast weights in male broilers was significant. breast weight, liver weight and abdominal fat in female broilers in line b were significant and higher than female broilers line a but food conversion rate was no significant. liver weight and abdominal fat were significant between males and females in parental line but, only breast weight between male and female in line b was significant. the growth rate of birds in line b during 17 to 35 day of age was higher than that in line a. moreover the growth rate in male birds during 17 to 54 day of age was higher than that in female birds.