Hormone levels and angiogenesis contribute to the competition between myogenesis and adipogenesis in broiler breast muscle during growth.

Rapid muscle growth suppresses intramuscular fat deposition in chickens, leading to decreased meat quality; however, the underlying mechanism remains unclear. Here, we compared differences in myogenic and adipogenic properties in the breast muscle of Ross 308 (RS) and Xueshan (XS) broilers during growth, and analyzed the contribution of hormone levels and vascular density to these differences. Our results showed that body weight, breast muscle ratio, and myofiber size were significantly greater in RS broilers from embryonic day 12 (E12), and these differences became more pronounced after day 21 (D21), which was accompanied by marked increases in the abundance of PAX7⁺ satellite cells (SCs) and enhanced expression of PAX7, MYF5, MYOD, and MYOG. In addition, higher levels of T3, T4, and IGF-1 were found in both yolk and serum of RS broilers from E12 to D42. In contrast, XS broilers exhibited greater intramuscular fat deposition before hatching, which was accompanied by greater number of TCF4⁺ fibro/adipogenic progenitors (FAPs) and enhanced expression of PDGFRA and ZNF423. Consistently, the number of CD31⁺ endothelial cells and expression of CD31 and VEGFA were also higher in XS broilers from E12 to D1, suggesting that enhanced angiogenesis supported FAPs proliferation. Therefore, the rapid muscle growth and enhanced myogenic capacity of SCs suppressed the proliferation and adipogenic differentiation of FAPs in broilers, with hormone levels and angiogenesis playing regulatory roles. These findings provide valuable insights into the competing mechanism of myogenesis and intramuscular adipogenesis in broilers.