Selection of Japanese quail for contrasting blood corticosterone response to immobilization

Japanese quail (Coturnix coturnix japonica) were divergently selected for 12 generations for increased (high stress, HS) and decreased (low stress, LS) blood corticosterone (B) response to unfamiliar environments. Response lines were selected initially on the basis of wild-type quail B response to albino (ALB) quail intrusion (S1 to S3) and subsequently on B response to immobilization (IMB) (S4 to S12). Using ALB intruders as stressors proved unsuccessful, therefore the practice was abandoned in favor of using IMB, which proved successful. Across nine generations of selection, using the IMB stressor, the HS line exhibited a mean serum B response that was approximately 58% greater than that of the random-bred (control stress, CS) line, whereas the LS line had a mean response approximately 23% less than that of the CS line. Selection differentials were approximately three-fold greater in the HS than in the LS line whereas realized heritabilities (h2) were approximately two-fold greater in the HS than in the LS line.