A comparative study of libido in drakes: from phenotypes to molecules

Low fertilization rate is the main reason to limit the development of artificial insemination (AI) technology in ducks. However, the libido of male livestock has been confirmed to be related to semen quality and fertilization rate, and we found that the libido of drakes was different. Thus, the research on the libido of drakes may be the key to further develop and apply AI technology. In this research, we established the first scoring standard for libido evaluation in drakes based on the performance of drakes during training period. Phenotypically, the body weight of high libido group was lighter than that of the other groups, while the weight of testis and epididymis in the high libido group was higher than that in the low libido group. Furthermore, we constructed the first expression profile of hypothalamus, pituitary, testis, and epididymis of drakes with high or low libido. There were 2, 1822, 214, and 892 differentially expressed genes (DEGs) in hypothalamus, pituitary, testis, and epididymis. The expression and sequence of Translocation Associated Membrane Protein 2 (TRAM2) were different in high and low libido drakes, indicating that it may be a candidate gene related to drake's libido. The estrogen, prolactin, and oxytocin signaling pathways were all activated in the pituitary of the low libido group. Meanwhile, the metabolic and oxidative phosphorylation pathways were enriched by DEGs in pituitary, testis and epididymis. Our research reveals that the difference in metabolic may cause changes in body weight of drakes, resulting in altered hormone levels and oxidative phosphorylation of gonad, which negatively affects libido and spermatogenesis in drakes. These results provide novel insights into the avian libido and will help better understand the underlying molecular mechanisms.