Turkey muscle growth and focal myopathy.

Muscle structure and blood enzyme activity were studied to 16 wk of age in lines of turkeys selected for rapid growth. The body and carcass weights were measured, frozen sections of breast and leg muscles examined, and plasma creatine kinase (CK) levels determined. Muscle weights were usually proportional to BW except for the relatively larger superficial pectoralis (SP) muscles in the most rapidly growing line. Damaged muscle fibers were found in all muscles examined, especially in the SP of the breast, the gastrocnemius (GA), and other muscles of the leg; these damages became more common from 10 to 16 wk of age. There were more degenerating muscle fibers and higher levels of plasma CK in the rapidly growing lines than in a slower growing unselected line. The findings support the idea that a focal myopathy, unrelated to deep pectoral myopathy or to inherited muscular dystrophy of the chicken, is associated with rapid growth of turkeys.