Muscle fiber types in the dystrophic puboischiofemoralis of commercial broilers.

Muscle fiber types, their diameters, lipid content, and nuclei distributions were studied in normal and necrotic puboischiofemoral muscles from commercial broiler chickens of the Hubbard strain. Three categories of puboischiofemoral fiber morphology (alpha R, beta R, and alpha W) occur in the cranial and caudal portions of the pars lateralis and in the cranial, medial, and caudal portions of the pars medialis. The greatest amount of necrosis occurred in the caudal portion of the pars medialis of the puboischiofemoralis. A fiber type characterized by a greatly enlarged and rounded or oval cross-section, decreased fat content, and internalized and clustered nuclei was present in necrotic muscle but not in normal muscle.