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.

T-maze behavior and early egg production in Japanese quail selected for contrasting adrenocortical responsiveness.

Broiler chicks that traverse a T-maze quickly to reinstate contact with their companions (HP, high performance) are known to grow faster, be more social, and exhibit a reduced plasma corticosterone (B) response to acute stress than slower (LP, low performance) chicks. Genetic lines of Japanese quail selected for reduced (LS, low stress) or exaggerated (HS, high stress) plasma B response to brief restraint also differ in sociality and performance. In the present study, we asked if divergence in early T-maze behavior was associated with differential attainment of puberty and early egg production in these lines. At 3 d of age, LS and HS quail were categorized as HP or LP birds based on running times in a T-maze. Thus, there were four treatment combinations: HP-LS, HP-HS, LP-LS, and LP-HS birds. Daily egg records were kept for 8 wk. The average ages at first egg lay (FIRST), at 25% egg production (A25% EP), and weekly and cumulative hen-day egg production (HDEP) where calculated. Daily egg weight (EWT) data were also collected, and BW measures were made at the end of the trial. Mean FIRST and A25% EP responses were lower (P < 0.02) and cumulative HDEP was greater (P < 0.04) in HP than in LP quail. Despite considerable numerical reductions in FIRST and A25% EP, as well as 5% elevation in cumulative HDEP in LS quail, line differences in these variables were not significant. On the other hand, FIRST and A25% EP were reduced (P < 0.05) in HP-LS quail when compared to LP-HS ones, whereas HP-HS and LP-LS quail showed intermediate and similar responses that did not differ from the other two treatment groups. Mean cumulative HDEP findings for the interactive effect of performance category with line mimicked these puberty findings. EWT and BW measures were not affected by any of the treatments or their interactions. Our results suggest that rapid negotiation of the T-maze by quail chicks is associated with accelerated puberty and increased HDEP in quail of two genetically diverse lines. This effect is particularly evident in quail selected for reduced adrenocortical responsiveness, suggesting possible additive effects.