New insights into the skeletal muscle circadian clock in ruminants.

Circadian rhythms are endogenous oscillations with a period of approximately 24 h. They enable organisms to anticipate and adapt to daily environmental changes, such as light and temperature. As the largest metabolic and motor organ in the body, skeletal muscle plays a decisive role in determining meat production efficiency in ruminants. Skeletal muscle development is largely governed by the proliferation and myogenic differentiation capacity of skeletal muscle satellite cells (SMSCs). More than 2,300 genes in skeletal muscle exhibit circadian oscillatory expression and are extensively involved in myogenesis, transcriptional regulation, and metabolic processes. The rhythmic expression of these genes is modulated by external factors including the photoperiod, feeding behavior, gut microbiota, and physical activity. Disruption of the endogenous circadian timing system can inhibit SMSC proliferation and myogenic differentiation, thereby impairing normal muscle development. Therefore, this review focuses on key management aspects of ruminant production-such as environmental control, nutritional regulation, and exercise management-and systematically elaborates on how these husbandry strategies may influence SMSC fate by modulating the circadian clock, along with the underlying molecular mechanisms.