The investigation of molecular mechanisms influencing variations of sternum calcification in ducks by integrating transcriptomic and metabolomic analyses.

In ducks, the sternum is the largest flat bone. Its calcification affects breast muscle development, health, and economic value. Delayed calcification can lead to sternum fractures during feeding, slaughter. Thus, we need to understand the molecular basis of sternum calcification. We compared two duck breeds with different body sizes: the fast-growing, large-bodied Cherry Valley (CV) and the smaller-bodied Huaifu (HF) ducks. Results showed a positive correlation between sternum calcification rate and both calcification length and breaking strength (r > 0.4). HF had a higher calcification rate (99%) than CV (95%), and females (HFM: 100%; CVM: 97%) had higher rates than males (HFG: 97%; CVG: 94%). Breaking strength was also higher in HF (43.29 N) than in CV (36.1 N), with females outperforming males. We performed RNA-seq and LC-MS metabolomics on sternal tissues. A clear contrast in gene expression appeared between nearly fully calcified Huaifu males (HFG) and females (HFM): genes including FGF6, BDNF, HTR4, MYLK2, MAP3K6, and CER1 were barely expressed. But these genes were significantly upregulated in CV compared to HF, in CVM compared to CVG, and in high-breaking-strength (HB) versus low-breaking-strength (DB) groups. Those genes showed low expression in fully calcified or non-calcified sterna but high expression during active calcification, suggesting they help drive calcification. Our study identifies multiple biomarkers linked to duck sternum development and offers new insights into avian sternum ossification, which may help improve poultry production and welfare.