Selection of Japanese quail for reduced adrenocortical responsiveness accelerates puberty in males.

Differences in the onset of puberty were assessed in male Japanese quail from a random-bred (RB, control) line and two lines that had been genetically selected for reduced (low stress, LS) or exaggerated (high stress, HS) plasma corticosterone response to brief mechanical restraint. At 42 d of age, cloacal gland area (CAREA) and volume (CVOL), proportion of individuals that produced cloacal gland foam (PICF), and intensity of cloacal gland foam production (CFP) were examined in 60 representatives from each of these quail lines. CFP was quantified by subjective scaling of the amount of foam ejected upon manual expression (squeezing) of the foam gland, using a scale of 1 (no foam expressed) to 5 (maximum amount of foam expression). Mean CAREA and CVOL were similar in quail of the RB and HS lines, but these measures were greater (P < 0.01) in the LS quail. In addition, more (P < 0.05) LS than HS birds expressed foam at 42 d, whereas RB quail exhibited an intermediate PICF response that was not different from either selected line. CFP results mimicked those found for PICF (i.e., LS quail produced a greater (P < 0.05) amount of foam than HS birds, whereas RB quail showed intermediate production that was not different from LS or HS levels). In prepubertal and pubertal Japanese quail, cloacal gland hypertrophy is androgen-dependent and highly positively correlated with testes size as well as sexual activity. Cloacal gland foam production is also considered a reliable indicator of testicular size and activity. Thus, we conclude that selection for reduced adrenocortical responsiveness in Coturnix is associated with acceleration in the onset of puberty in males. The potential interaction between adrenocortical and testicular activity as it relates to male reproductive performance is discussed.