Histology and matched multi-omics profiling resolve developmental transitions in Wugang Copper Goose leg muscle

Wugang Copper Goose is an indigenous meat-type breed, but the molecular events accompanying leg muscle development around hatch remain unclear. We examined breast and leg muscle histology at embryonic days 15 (E15), 19 (E19), 23 (E23), and 28 (E28) and posthatch day 1 (P1). Transcriptomic, proteomic, and metabolomic profiling of leg muscle at E15, E23, and P1 used matched samples from the same five individuals per stage. Leg muscle fibers became progressively organized before hatch and enlarged markedly at P1, and multi-omics analysis distinguished two developmental transitions. From E15 to E23, increasing cytoskeletal and calcium-signaling programs accompanied lower DNA-replication- and nucleotide-related signals, consistent with structural assembly and declining replication-related activity. From E23 to P1, fiber enlargement coincided with higher oxidative phosphorylation, citrate-cycle, peroxisome proliferator-activated receptor signaling, and fatty-acid-associated programs and lower proliferative programs. RNA and protein fold changes were moderately concordant across both transitions (Spearman ρ = 0.55 and 0.58), whereas metabolite changes were largely layer specific. Reverse-transcription quantitative PCR (RT-qPCR) supported the directional expression patterns of eight representative genes. Together, these data distinguish an early transition from replication-related activity to structural assembly and a posthatch transition dominated by oxidative and lipid-associated maturation.