Temporal trends in porcine and bovine semen characteristics: A retrospective long-term analysis of semen production data.

Artificial insemination (AI) is frequently used in cattle and pig production, and semen quality is crucial to both genetic advancement and successful reproduction. While several studies have documented deteriorating semen quality in humans, dogs, and horses, knowledge about long-term trends of bull and boar semen quality is insufficient despite its biological and economic significance. The present study aimed to assess temporal trends in semen quality parameters in bulls and boars over a period of 18 and 22 years, respectively, using production data collected at a single German AI center for each species. A retrospective analysis of semen characteristics, including ejaculate volume, sperm concentration, total sperm motility, and sperm output, was performed on 47,757 bull ejaculates collected between 1997 and 2019 and 619,368 boar ejaculates collected between 2005 and 2023. Temporal trends were evaluated using linear regressions. The analysis revealed a significant increase in sperm concentration and total sperm motility for both bulls and boars. The decrease in ejaculate volume in both species did not negatively affect overall sperm output, which showed an increasing trend in line with sperm concentration and total sperm motility for bulls as well as boars. All observed trends were highly significant (P < 0.001). Results contrast findings in other species and highlight the efficiency of breeding strategies in the cattle and pig industry, improving not only production traits but also reproductive performance.