Restricted selection indices for simultaneous improvement of antagonistic traits in egg type chickens
SANDEEP NARWAL, C.P.MALIK, D.S. DALAL AND DIDAR SINGH
Department of Animal Breeding, CCS Haryana Agricultural University
This study was conducted on 765 progenies produced from 87 sires of strain H of White Leghorn. The traits included were body weight at 20 weeks of age (BW20), age at first egg (AFE), egg production upto 40 weeks of age (EP40), egg weight at 40 weeks of age (EW40) and clutch size from 31 to 40 weeks of age (CS2). Data were analysed by using Harvey’s least squares technique. Twenty six multitrait indices were constructed combining all these traits in all possible combinations considering aggregate genotype of EP40 and EW40 with relative economic value as 1.0 and 0.5, respectively, considering selection intensity as 1.40. Hundred per cent restriction was applied on AFE in I 1 (base index of 5 traits), I 3 (best 4-trait index), I 16 (best 3-trait index) and I 25 (best 2-trait index) indices. Hundred per cent restriction on AFE caused heavy reduction in accuracy of selection (R IH) of all the four indices. Aggregate genetic gain, genetic gain in individual trait and heritabilities of indices were reduced considerably in all the four restricted indices as compared to respective unrestricted indices. The best restricted index was IR 3 combining EW40, AFE (with 100% restriction), EP40 and CS2 having R IH value, relative efficiency (to unrestricted base index), aggregate genetic gain and heritability as 0.3369, 66.90 per cent, 0.6936 and 0.1644, respectively. Through the application of this index the expected response would be 0.1094g, 000 days, 1.1684 eggs, 1.7968g and 0.0427 eggs in EW40, AFE, EP40, BW20 and CS2, respectively.