Seasonal differences in plasma testosterone profiles in buffalo bulls

Testosterone was measured by radioimmunoassay in blood samples collected hourly over 10 h from two adult buffalo bulls in April, May, August and December. The basal concentrations were below 0.2 ng/ml while peak concentrations ranged from 0.35 to 1.65 ng/ml, with not more than one complete peak occurring during a 10 h period. Both bulls had similar testosterone profiles within each sampling period but differences were evident between periods, the mean concentration being highest in August and falling through December and April to the lowest levels in May. Testosterone concentrations in buffaloes are therefore lower than those in other domestic species, and appear to vary during different times of the year.