Integrative Transcriptomic and Genomic Analysis Reveals the Regulatory Mechanisms Underlying Semen Quality Stability in Ganders

Semen quality significantly affects the reproductive performance of ganders. As seasonal breeders, ganders typically experience a decline in semen quality over the breeding season; however, the mechanisms regulating semen quality stability during this period remain poorly understood. Maintaining high semen quality throughout the entire breeding season is crucial for improving production efficiency. In this study, we systematically investigated the semen quality parameters of Tianfu Meat Goose II ganders at three distinct stages of the female geese's annual laying cycle: early (36-week-old), peak (47-week-old), and late (66-week-old) laying stages. The results showed that the ganders in stable (S) semen quality group exhibited superior semen quality parameters compared to those in unstable (U) semen quality group. Notably, the gander semen quality factor (SQF) and sperm density were significantly higher in the S group than in the U group (P < 0.05). Histomorphological analysis revealed that the testicular weight and size of ganders from the S group were significantly greater than those from the U group (P < 0.05), and so were the numbers of testicular spermatids and spermatozoa (P < 0.05). Through a combination of transcriptomic and selective sweep analysis, protein-protein interaction network construction, and RT-qPCR validation, four hub genes (EP300, RAB31, PRKG1, and PIK3R1) and their significantly enriched KEGG pathways including adherens junction, gap junction, endocytosis, TGF-beta signaling, and Toll-like receptor signaling were identified to have important roles in regulating gander semen quality stability. Specifically, much higher levels of testicular EP300, RAB31, and PRKG1 expression might be associated with impaired semen quality in ganders from the U group, whereas the upregulated expression of PIK3R1 in testes of ganders from the S group appeared to play protective roles in maintaining the gander semen quality stability. These findings would provide novel insights into the molecular mechanisms underlying semen quality stability in ganders during the breeding season and offer valuable references for genetic selection and reproductive management in waterfowl breeding programs.