Scrotal Size EBVs are estimates of the genetic differences between animals in scrotal circumference at 400 days of age. Scrotal Size EBVs are expressed in centimetres (cm) and are calculated from scrotal circumference measurements taken on bulls between 300 and 700 days of age.
Increased scrotal circumference is associated with increased semen production in bulls, and earlier age at puberty of bull and heifer progeny. Increased scrotal circumference also has a favourable relationship with days to calving, such that bulls with larger scrotal circumference tend to have daughters with shorter days to calving.
Larger, more positive, Scrotal Size EBVs are generally more favourable. For example, a bull with a Scrotal Size EBV of +4 cm would be expected to produce sons with larger testicles at yearling age and daughters that reach puberty earlier than the progeny of a bull with a Scrotal Size EBV of -4 cm.