Relationship between bull signalment and testicular attributes in a Kenyan bull station

Background and Aim: Male fertility is essential to bovine reproduction, particularly when bulls are used for artificial insemination or single-sire breeding. Bull breeding and soundness examinations (BBSE) are routinely undertaken to identify potentially unfit bulls for breeding. Multiple criteria, including physical examination and determination of testicular and semen parameters, characterize BBSE. Knowledge interstices within this realm, especially in tropical African settings, necessitate pragmatic approaches to address the same. This study aimed to investigate the potential effects of bull parameters on testicular attributes in a tropical setting. Materials and Methods: The present study recruited healthy bulls (n = 96) aged >16 months with active semen collection used for artificial insemination at the Kenya Animal Genetic Resources Center. The breed breakdown was as follows: Ayrshire (n = 40), Boran (n = 3), Friesian (n = 36), Guernsey (n = 5), Jersey (n = 7), and Sahiwal (n = 5). Age, breed, body weight, scrotal circumference (SC), and testicular echotexture were collected, and the findings were analyzed using R statistical software. Results: SC increased with age and body weight (p < 0.0001). SC varied from one breed to the others (p < 0.0001). Furthermore, as determined using trans-scrotal ultrasonography, hyperechoic testicular lesions were present in 30.21% of the bulls imaged, and the incidence was significantly related to age (p < 0.001). Conclusion: SC is significantly affected by age and body weight. The mean SC was higher in the Bos indicus, but this finding is only indicative because the Sahiwal and Boran sample sizes were small. Notably, the prevalence of hyperechoic testicular foci following trans-scrotal ultrasonography was common in older bulls. However, there is a need to further elucidate this phenomenon’s pathophysiology with age as the etiology and possible sequelae of semen quality. Keywords: age, body weight, breed, scrotal circumference, testicular ultrasonography.