Department of Poultry Sciences, College of Agriculture, Tarbiat Modarres University of Tehran, Tehran, Iran
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 hundred and 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 replicates of floor pens of 17 chicks, except the male Cobb hybrid which had five replications. All groups were managed in a similar way throughout the 56 days of study. Daily feed intake (FI) and daily body weight gain (BWG) were measured on weekly basis and the European production index (EPI) were calculated at 49 and 56 days of age. There were no significant differences among hybrids in FI during starter and grower periods (P>0.05), although significant differences were observed in finisher period (P<0.01). Differences in daily FI were significant between male and female chicks in grower and finisher periods (P<0.05), but not in starter period. Differences in daily BWG were significant among hybrids throughout the experiment (P<0.01). Sex significantly affected the daily BWG in all periods (P<0.01). The calculated EPI showed significant differences for both 49 and 56 days of age among hybrids and between two sexes (P<0.01). There were no significant differences among hybrids in carcass yield, percentage of breast and abdominal fat to carcass weight at 42 and 56 days of age. On day 42, males had more percentage of carcass and breast yield compared with females (P<0.01). Percent of abdominal fat in females on day 56 was more than that of the males (P<0.01), while on day 42 no significant differences were found in this respect.