SELECTION FOR EGG-PRODUCTION .2. CORRELATED RESPONSES IN SEXUAL MATURITY, EGG WEIGHT AND BODY-WEIGHT OF 4 STRAINS OF WHITE LEGHORN

Four strains of White Leghorn were subjected to Osborne index selection for egg production up to 280 days of age for 4 generations. Correlated responses in sexual maturity, egg weight and body weight along with the selected strains. Egg number was negatively correlated with sexual maturity, egg weight and body weight at 40 weeks in all the 4 strains; whereas with body weight at 20 weeks showed positive correlation for IWN strains. Sexual maturity was positively correlated with egg weight but it was in differential direction and magnitude with body weights. Egg weight and body weights at 20 and 40 weeks were positively correlated. Similarly strong positive association between body weight at 20 and 40 weeks of age was recorded. The realized genetic correlated response per generation showed significant reduction in age of sexual maturity in all the 4 strains (-2.9 to -3.7). Negative regression coefficients for egg weight (-0.3 to 0.5) as well as for body weight at 40 weeks (-4.1 to -11.9) were recorded. Body weight at 20 weeks showed positive correlated response (10.3 to 33.3). Realized genetic responses were higher than the predicted responses. The positive response to egg number was partly associated with early age at first lay and smaller egg size.