Comparison of growth performance and carcass characteristics of six commercial broiler chicks.

An investigation was carried out to evaluate the growth performance of six commercial broiler hybrids available in Iran (Arbor Acres, Arian,Cobb 500,Hubbard, Lohmann and Ross 508).Two hundreds fifty fertile eggs of each hybrid were taken from different breeder farms, all over the country. The similarity of flocks ages and their health conditions were considered. After hatching, the sexed chicks were randomly assigned to six floor pens of 17 chicks, except the male cobb hybids which had Five replications. All groups were managed in similar way throughout the 56 days of study.Daily feed intake (FI), daily body weight gain (WG) and feed conversion ratio (FCR) were measured on weekly basis, and the European production index (EPI) were calculated for 49 and 56 days of age. There was no significant difference among hybrids in feed intake during starter and grower periods (p0.05), although significant differences were observed in finisherperiod (p0.01). Differences in daily feed intake were significant between male and female chicks in grower and finisher periods (P0.05), but not in starter period. Differences in daily body weight gain were significant among hybrids through experiment (P0.01). Sex significantly infuenced the daily body weight gain in all periods (P0.01). Differences in feed conversion ratio were significant for hybrids in starter and grower periods (P0.01), but it was not significant in finisher period (P0.05). There was no significant difference in FCR between sexes during the experiment. The calculated EPI showed significant differences for both 49 and 56 days of age among hybrids and between sexes (P0.01). There were no significant differnses among hybrids in carcass yeild, breast and abdominal fat percentage on 42 and 56 days of age. On 42 days of age, males had more percentage of carcass and breast compared with females (P0.01).Percent of abdominal fat in females on 56 days was more than that of the males untile the 42 days of age, and no significant differences was found in this respect.