The relationship between age and genotype and the growth of commercial meat strain chickens.

: Sex-linked dwarf male (dw/dw) and female (dw/-) chickens from a commercial meat strain, grew significantly slower than genetically normal broilers (Dw/Dw). The differences were evident at 2 weeks of age and they remained constant with age, at least through 8 weeks. The dwarfs in turn grew significantly faster than genetically normal (Dw/Dw) but slow-growing roaster strain chicks. Heterozygous (Dw/dw) normal, fast-growing male broilers grew significantly faster than the normal and roaster chicks but weighed 8% less than the normal broilers at 8 weeks. Abdominal fat accretion was greatest in the dwarf chicks and least in the slow-growing roaster strain when comparisons were made at the same age and the same body weight. Pectoralis muscle growth was greater in the broiler strain when equal age and weight comparisons were made. Gastrocnemius muscle growth, however, was greatest in the slow-growing roaster chicks.