Diurnal, premating, and postmating testosterone levels in roosters genetically selected for mating frequency

Circulating testosterone (T) levels were measured in roosters from lines genetically selected for high (HM) and low (LM) mating frequency and the randombred control (AC) base population. Lights were provided from 0600 through 2000 hr. A dirunal profile was determined by sampling at 0600, 1200, 1800, and 2400 hr. Plasma T levels prior to mating, immediately after mating, and 1 and 3 hr after mating were measured. By 1800 hr, AC males had higher T levels than both HM and LM males, which had levels that were similar to each other. Testosterone was at a minimum at 0600 hr and peaked at 2400 hr. Lines differed significantly both before and after mating with AC males highest, HM males intermediate, and LM males lowest. Control males had higher than baseline values prior to and after mating. Testosterone levels of AC males were correlated with their mating frequencies.