Characterization of muscle fiber type in the Pectoralis major muscle of slow-growing local and commercial chicken strains

The study aimed to characterize muscle fiber type of the Pectoralis major muscle of slow-growing chickens belonging to Padovana purebreed and to the commercial hybrid Berlanda gaina and their crosses. Forty-five chickens (both males and females) from the different genotypes were grown up to 180 days. Histochemical and morphometrical analysis were performed to characterize muscle fiber types, myofiber density and myofiber size of the different genotypes. The effects of genotype, sex and their interaction were estimated. Muscle samples appeared almost entirely made up of IIB fiber type, whereas a low percentage of area (5 to 6%) was composed of hypercontracted fiber. Myofiber density was significantly higher (P<0.05) in Padovana strains and cross sectional area was significantly lower (P<0.01) than in Berlanda strain. Muscle fiber characteristics appeared not to be affected by interaction genotype x sex.