Proteomic and functional characterization of seminal and epididymal plasma proteins associated with male fertility in cattle: A comprehensive review.

The animal industry is associated with substantial economic losses due to infertility and subfertility, with male infertility being a major contributing factor to breeding failure. Studies in cattle have shown that a significant proportion of these failures is primarily attributed to semen quality rather than female-related factors. Seminal plasma is a complex, protein-rich biological fluid composed of secretions from accessory sex glands and the cauda epididymis, containing functionally distinct groups of proteins such as enzymes, structural proteins, antioxidant proteins, and immune-modulatory factors. These proteins are involved in key reproductive processes including sperm motility regulation, capacitation, sperm-oocyte interaction, and protection against oxidative and immunological stress. Rather than individual protein listing, key functional protein groups such as fertility-associated glycoproteins, antioxidant enzymes (e.g., glutathione peroxidase), and molecular chaperones (e.g., heat shock proteins) have been shown to influence sperm function, with several studies reporting that these proteins are differentially expressed, showing approximately 1.5-3.0-fold higher abundance in high-fertility bulls compared to low-fertility counterparts. This review systematically synthesizes proteomic studies on cattle across different geographical regions, providing insights into how variations in seminal plasma protein composition contribute to fertility phenotypes. Furthermore, it highlights the potential application of these proteins as quantitative biomarkers for fertility prediction and as molecular targets to improve semen preservation and assisted reproductive technologies in livestock systems.