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.

Developmental profile of plasma androgens in cockerels genetically selected for mating frequency.

Plasma levels of androstenedione (AE), testosterone (T), and dihydrotestosterone (DHT) were measured at 1, 56, 112, and 168 days of age by radioimmunoassay in lines of cockerels divergently selected for male mating frequency. Values for total androgen (total A = AE + DHT + T) were also computed. No significant differences in mean hormone values were found between lines at any age. Hormone patterns throughout development were also similar for both lines. Plasma AE and T increased between Days 1 and 56, stabilized through Day 112, and rose again prior to 168 days of age. In contrast, DHT levels were low throughout Day 112 and rose significantly by Day 168. Total A in the high mating line was low throughout Day 112 with significant increases occurring by Day 168. In the low mating line, total A was low on Day 1, increased significantly by Day 56, and it remained unchanged through Day 112. Peak values occurred by Day 168. Within line correlation analyses between AE, T, DHT, and total A revealed a more uniform hormonal state throughout development in the high mating line than in the low mating line. Because no differences were found between the mating lines in baseline levels of individual androgens or in concentration patterns of androgens up through the attainment of sexual maturity, it appears that neither posthatch baseline levels nor posthatch temporal androgen concentrations control male sexual behavior in the mating lines of birds.