Effects of bull parameters, testicular echogenicity, and scrotal circumference on semen traits

Background: Africa is the fastest-growing continent, with more than half of the global population growth expected to occur in the region by 2050.The increasing population and lifestyle changes translate to high demand for food.However, Africa does not produce enough food to cater to its population.The current study sought to bridge knowledge gaps in the dairy and beef production systems by addressing factors affecting semen production in bulls used for AI at the Kenya Animal Genetic Resources Center.Methods: A total of 88 bulls met the inclusion criteria (> 16 months, healthy, and in active semen collection).The breed breakdown was as follows; Ayrshire (n = 39), Friesian (n = 34), Jersey (n = 7), Boran (n = 3), and Sahiwal (n = 5).Bull characteristics (age, breed, body weight, BCS), testicular attributes (SC and testicular echotexture), and semen parameters (semen volume, forward progressive motility, sperm concentration, and post-thaw motility) were determined, and results were analyzed using R statistical software.Results: Semen volume significantly increased with body weight, age and SC (p < 0.001-0.05).Sperm concentration significantly decreased with increased BCS (p < 0.05).Breed significantly affected semen volume and sperm concentration (p < 0.01-0.05).Hyperechoic testicular lesions noticed in older bulls did not significantly affect semen quality (p > 0.05).Conclusions: These findings will inform bull selection and culling criteria, highlighting that bulls presumed overdue for culling can still produce high-quality semen (the oldest bull at the time of data collection was aged 140 months).Further studies elucidate the relationship between increased testicular echotexture and semen parameters.