Age effects on muscle-related gene expression and glycogen levels in broiler chickens (Gallus gallus domesticus)

Muscle regulatory factors MYF5, MYH7, and MYOG are essential for muscle growth and development; thus, they are considered applicant genes for meat production traits in chickens. This study investigated the levels of glycogen and the expression of MYF5, MYH7, and MYOG genes in the pectoralis major muscle in broiler chickens. Fresh specimens were collected from the pectoralis major muscle for this study. Special stains were employed for identifying the histological structure and glycogen content in the pectoralis major muscle. The highest mean of the muscle fiber area, thickness of the connective tissue layers, and muscle bundle area was recorded at 38 days. The muscle fibers of the pectoralis major showed a progressive increase in PAS staining intensity from 7 to 21 days old, followed by a decline at 38 days old. qPCR was employed to estimate the mRNA concentrations of MYF5, MYH7, and MYOG in the muscle fibers in the pectoralis major muscle. In fact, the expression at 7 days exhibited that the highest average expression was detected in MYF5, whereas at 21 days, it revealed that there were no significant changes in gene expression. On the other hand, the expression at 38 days showed that the highest average expression was detected in MYOG. In conclusion, this study demonstrates the essential function of muscle regulatory factors in the growth and development of the pectoralis major muscle in broiler chickens. The analysis showed a strong correlation between gene expression at various growth stages and the development of muscle fibers.