DIVERGENT SELECTION FOR BODY-WEIGHT AND YOLK PRECURSOR IN COTURNIX-COTURNIX-JAPONICA .9. EVALUATION OF TRAITS ASSOCIATED WITH ONSET OF SEXUAL MATURITY

An experiment was conducted to compare traits associated with onset of sexual maturity in Japanese quail lines. Lines divergently selected f or high and low 4-wk BW (HW and LW), and high and low total plasma pho sphorus at beginning of lay (HP and LP) were compared with a randombre d line (RBC1) that served as the base population for HW, LW, HP, and L P. The HW sublines (HW-HP and HW-LP) and LP subline (LP-HW) were also compared to their respective line of origin. Most of the differences o bserved for males selected for a single trait were found for weight-se lected rather than for phosphorus-selected lines. The patterns of sign ificance closely followed differences expected due to the extreme dive rsity in BW for the HW and LW when compared with RBC1. Females general ly matured approximately 2 wk later than males for HW, HP, and LP. Lin e LW females matured approximately 4 wk later than LW males. Differenc es were observed for variables associated with onset of sexual maturit y for HW, LW, and HP when compared with RBC1. Observed changes in carc ass variables for sublines were generally associated with reductions i n BW for HW-HP, and HW-LP versus HW and for increases in BW for LP-HW versus LP. The differences were likely due to the fact that two-trait selection (BW for males and total plasma phosphorus in females) has al lowed weights to diverge when compared with lines selected for single traits.