Homologous seminal plasma addition to thawed goat semen: impact on sperm quality parameters in vitro

Seminal plasma is typically removed during the cryopreservation of goat sperm, yet its reintroduction post-thaw has been proposed as a strategy to enhance sperm quality in other species. Despite variable outcomes across species and studies, seminal plasma plays key roles in modulating sperm function and interacting with the female reproductive tract. This study aimed to evaluate the in vitro effects of adding homologous seminal plasma to thawed goat buck semen at different concentrations and from ejaculates of varying initial sperm motility. In the first experiment, thawed samples were diluted with increasing proportions of seminal plasma (1:0, 1:0.25, 1:0.50, 1:0.75, 1:1; volume: volume). After 2 h (h) of incubation at 37 °C, samples with higher proportions of seminal plasma (≥ 1:0.50) showed a significant decrease (P < 0.05) in plasma membrane integrity and a consistent increase in acrosome-reacted sperm compared to controls. In a second experiment, seminal plasma obtained from ejaculates classified by initial motility (very high, high, medium, low) was added to thawed sperm and compared to a control group that received a pooled sample consisting of seminal plasma from ejaculates of all quality categories. Sperm quality decreased when seminal plasma from very high-quality ejaculates was used, while slight improvements were observed with plasma from low-quality ejaculates. These findings suggest that the addition of homologous seminal plasma did not confer significant functional effects related to potential sperm fertility and that ejaculates not suitable for insemination may still serve as viable sources of seminal plasma.