Fat Deposition in a Broiler Sire Strain.

Cocks from four lines selected for a low amount of abdominal fat (AF), a favorable feed conversion ratio (FC), and high body weight after restricted (GR) or ad libitum (GL) feeding were mated to commercial broiler breeder hens. A total of 3,600 broiler progeny in three hatches from these matings was reared by line in litter pens. At 41 days of age GR and GL line progeny had significantly heavier body weights, poorer feed conversion ratio, and higher percentages of abdominal fat than AF and FC line progeny. At comparable body weights (AF, 1,893; FC 1,918; GR, 1,848; and GL, 1,897 g) feed conversion was most favorable for FC line progeny (1.72), AF and GL line progeny did not differ (1.77), and GR line progeny had the poorest feed conversion ratios (1.79). The AF line progeny had the lowest percentage abdominal fat (1.88%), followed by FC line progeny (2.20%), GL line progeny (2.91%), and GR line progeny (3.10%). As in the pure lines, selection for body weight after restricted feeding was not effective in obtaining leaner and more efficient chickens. When compared with differences between pure lines, results of the broiler progeny matings indicate that body weight, feed conversion, and percentage abdominal fat are inherited largely in an additive manner.