Divergent selection for mature body weight in dwarf White Leghorns. 1. Growth and reproductive responses to selection.
Genetic selection for high (H) and low (L) 20-week body weight (BW) in dwarf White Leghorns was practiced for three generations. The base population was the Oregon State University dwarf Leghorn population (C) selected previously for part year hen-housed egg production (EP), early sexual maturity (SM), and large initial egg weight (EW). Asymmetry of response was observed in both sexes. Realized heritabilities for 20-week BW for H and L males were .49 and .36 and for H and L females were .45 and .79, respectively. Twenty-week BW of the 3rd generation H and L line females were 1.48 and .80 kg, respectively, compared to 1.13 kg for the C line. Similar weights for the males were 1.74, .97, and 1.27 kg for the H, L, and C line, respectively. The H and L lines diverged significantly in 10, 20, 40, and 60-week BW, SM, and EW after one generation of selection and the divergence continued through the third generation. The EP and egg specific gravity did not differ among lines. The C line was intermediate to the selected lines for all traits except EP. The EW at 35 and 60 weeks differed between the H and L lines by 10 g at generation 3 and SM was 149 and 157 days for the H and L lines, respectively.
D000818:Animals; D001835:Body Weight; D002645:Chickens / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D005260:Female; D008297:Male; D010058:Oviposition; D010641:Phenotype; D012098:Reproduction; D012641:Selection, Genetic; D012741:Sexual Maturation