"Circumference measurements should be taken at the widest point on the scrotum.
Scrotal measurement
Depending on the breed type of the bull being tested, the minimum scrotal circumference can vary. Maximum testicular size usually occurs at 4 to 6 years of age. With advancing age, testicular tissue may lose some sperm-producing capacity.Therefore, scrotal circumference measurements are not as accurate after this time.The table below illustrates the minimum scrotal circumference (SC) that will allow a bull to pass a breeding soundness exam. However, bull buyers should not feel comfortable in accepting the minimum, but rather select bulls that are average or above average for the breed and the age of the bull.Therefore, the "Good" column of the following table is a better guideline for bull selection.
Recommended Scrotal Circumference
Age
Minimum SC (cm)
Good
< 15 months
30
> 34
15 -18 months
31
> 36
18 -21 months
32
> 37
21 -24 months
33
> 38
> 24 months
34
> 39
There is great variation in scrotal circumference between breeds of bulls. Measurement of many English and European bulls has shown that yearling bulls should have scrotal circumference of at least 30 cm and by 20 months of age have a scrotal circumference of at least 32 cm. Brahman breed bulls will have smaller testes at the younger ages, and they will reach maturity at an older age.The Brahman breed bulls will have adult scrotal circumferences similar to other beef breeds.
Source: Bryan Kutz, University Of Arkansas Ag Extension"
