Developmental changes of bull (Bos taurus) genitalia as evaluated by caliper and ultrasonography

The objective of the present study is to follow the growth of the testes and the pelvic genitalia in cattle bulls, using ultrasonographic examination and measurements of external genitalia by caliper. Six Friesian bulls were examined periodically from 3 to 24 months of age with 3-month interval. Scrotum circumference (SC) and length were measured by tape. Testicular length, width and depth were measured by caliper. Scrotal contents including testes and epididymis, and the pelvic genitalia including bulbourethral gland (BUG), prostate and seminal glands (SG) were examined using transrectal ultrasonography. Scrotal circumference, length and the three dimensions of the testes showed significant increase with the advancement of age. Significant correlation was present between SC and testes breadth. At the same time, testis breadth as estimated by sonar showed positive correlation with that estimated by caliper. A positive correlation was also found between testicular breadth with each of the BUG and SG. Finally, it was concluded that ultrasonography gave appreciable benefits in studying the developmental changes of the testes and accessory glands of growing bulls. The obtained data could provide a useful tool for predicting bull puberty and fertility.