Testosterone and Libido in Holstein Bulls of Various Ages

Abstract

Testosterone was measured by radioimmunoassay in the blood plasma collected from 197 and 195 Holstein bulls in the spring and fall seasons, respectively. Bulls ranged in age from 8 mo to 13.5 yr. The average value for spring was 8.0 ng/ml, higher than the value of 5.7 ng/ml in the fall. Also, there was a tendency for testosterone to increase with age of the bulls up to 6 to 7 yr. The concentration of circulating testosterone was unrelated to libido or semen quality. © 1976, American Dairy Science Association. All rights reserved.