Genetic characterization of stress responsiveness in Japanese quail. 1. Analyses of line effects and combining abilities by diallel crosses.

The inheritance of stress responsiveness (line effects and combining abilities) was phenotypically studied in progeny from diallel crosses of randombred (RB) quail and quail selected for exaggerated (high stress, HS) or reduced (low stress, LS) plasma corticosterone (CS) response to brief immobilization. The three genotypes were crossed in a 3 x 3 factorial arrangement of treatments that allowed all possible crosses between RB, LS, and HS males with RB, LS, and HS females. The nine crosses produced 479 progeny. At 28 d of age, quail of each cross were stressed by immobilization, and blood was sampled. Plasma CS was used to estimate stress responsiveness in the progeny of each cross. Estimates of the following genetic effects were made: average post-immobilization plasma CS response within each cross, general combining ability (GCA), and specific combining ability (SCA). Differences (P < 0.05) in plasma CS response to immobilization between crosses involving the LS and HS lines (HS crosses > LS crosses) were commonly observed. There were no significant differences in the means of plasma CS responses between males and females within each of the crosses except for the marginal (P = 0.07) sex difference (male > female) found within the LL cross (LS male with LS female). The GCA estimates were -1.23, -2.89, and 5.08 for the RB, LS, and HS quail, respectively. The SCA was not significant for any diallel mating except HH (P < 0.007). Line effects on plasma CS response were different from zero for the LS and HS lines.