Performance and heterosis for production traits of White Leghorn under family index selection

The mean performance of pure lines and per cent heterosis for economic traits in reciprocal crosses between two lines (IWH and IWI) of White Leghorn undergoing family index selection for part period egg production up to 280 days of age over six generations were evaluated. The traits measured on each pullet were age at sexual maturity (ASM), body weight at 20 (BW20) and 40 (BW40) weeks of age, 40th week egg weight (EW40) and part period egg production (EP280) up to 280 days of age. The crosses, in final generation, expressed positive heterosis for EP280, ASM, 20 and 40 week body weights, but there was negative heterosis for egg weight. The average heterosis for egg production to 280 days of age, egg weight, age at sexual maturity, 20 and 40-week body weight were 11.74, −1.83, 1.88, 5.85 and 0.78 per cent, respectively in the crosses produced after 6 generations of selection. The reciprocal crosses differed in the degree of manifestation of heterosis for almost all the traits suggesting the involvement of maternal/sex-linked effects in the expression of heterosis. Based on the average performance of pure lines, it could be concluded that the pure lines under study pertain to the elite flock, which can be exploited for developing the commercial layer strains.