Testosterone and libido in holstein bulls of various ages.
Testosterone was measured by radio-immunoassay 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.
D000367:Age Factors; D000818:Animals; D002417:Cattle / Q000502:physiology*; D007989:Libido / Q000502:physiology*; D008297:Male; D012621:Seasons; D012661:Semen / Q000502:physiology; D013739:Testosterone / Q000097:blood*
D013739:Testosterone