Degeneration of testicles is a common cause of reduced breeding efficiency. Young bulls are often fertility tested and then assumed to be fertile for the next 5 to 8 years. Testicle degeneration can be caused by prolonged hot weather, age, trauma, stress and diseases. Signs of degeneration include a decrease in testicle size, libido and a decrease in semen quality. An annual fertility test along with breeding soundness records will aid in detecting degeneration.
Scrotal circumference is an important and useful measurement in determining breeding ability.
Scrotal circumference has a positive relationship with larger mass of sperm-producing tissue, the percent normal sperm cells and the sexual maturity of female relatives. Bulls tested for fertility are usually scored according to the Breeding Soundness Evaluation System. Sperm motility, morphology and scrotal circumference are evaluated on a scoring system with scrotal circumference being most important. A bull must accumulate 60 points on the scoring system to be classified as good of which 40 may come from scrotal circumference, emphasizing its importance. A bull should be classified as a satisfactory, questionable or unsatisfactory potential breeder.