DIVERGENT SELECTION FOR BODY-WEIGHT AND YOLK PRECURSOR IN COTURNIX-COTURNIX-JAPONICA .10. RESPONSE TO SELECTION OVER 30 GENERATIONS

Japanese quail lines were divergently selected for 30 generations for 4-wk BW (HW, LW) or plasma yolk precursor (HP, LP) as measured by tota l plasma phosphorus (TPP) at the beginning of lay. The HW, LW, HP, and LP lines were initiated from a randombred control line (R1). Tn the n inth generation of selection in the HW line, sublines were developed b y continuing to select males for increased 4-wk BW whereas females wer e selected for increased (HW-HP line) or decreased (MN-LP) TPP. Indivi dual selection was used in the HW, LW, HW-HP, and HW-LP lines. In the HP and LP lines, females were individually selected whereas males were selected on their full-sisters' performance. Realized heritabilities (h(2)), based on the Linear regression of selection responses (correct ed for environmental changes) on accumulated selection differentials ( weighted for the number of offspring produced) over generations, decli ned with selection in the HW, LW, HP, and LP lines. The h(2) of 4-wk B W in the HW line was 0.42 during the first 10 generations of selection and then declined to 0.30 during the next 20 generations of selection . In the LW line, realized h(2) of 4-wk BW was 0.40, 0.16, and -0.12 i n Generations 1 through 10, 11 through 20, and 21 through 30, respecti vely. The respective h(2) for TPP in the HP line were 0.29, 0.17, and 0.14. The h(2) of TPP in the LP line was 0.35 during the first 10 gene rations and essentially zero during the next 20 generations. Four-week BW and TPP were negatively associated in the HW, HT, and LP lines. Th ere was no significant relationship between these two traits in the LW line.