Untargeted Metabolomic Profiling of Spermatozoa and Seminal Plasma Identifies Candidate Metabolic Indicators of Semen Quality in Holstein Bulls

Abstract

Simple Summary Reproductive efficiency is crucial for the economic success of dairy farming. Because a single bull can inseminate thousands of cows, poor semen quality leads to significant financial losses. However, standard evaluation methods cannot fully explain why some bulls produce better quality semen than others. This study aimed to uncover the underlying biological differences by examining the chemical composition of both sperm cells and the surrounding seminal fluid from Holstein bulls. We used advanced chemical analysis to measure small molecules, known as metabolites, in samples from thirty bulls classified as having either high-quality or low-quality semen based on long-term records. As a result, we identified 46 LC–MS features (44 unique) in spermatozoa and 11 features (9 unique) in seminal plasma. Bulls with high-quality semen consistently showed higher levels of molecules involved in cellular energy production and protein building blocks. These findings suggest that specific chemical signatures are strongly linked to better semen quality. Ultimately, this research provides new insights into reproductive biology and could eventually help breeding programs select superior bulls, improving the sustainability and profitability of the global dairy industry.