Multi-trait selection indices for improving egg mass in egg type chicken

The data on 786 pullets, produced from 29 sires mated with 124 dams, were utilized to construct and evaluate the relative efficiency of different multi-trait selection indices for improving egg mass at 40th week of age by incorporating various traits in a pure strain (N) of White Leghorn. A total of 57 indices were constructed in combinations of six, five, four, three and two traits as the selection criteria with objective in all the cases being improvement of egg mass. The indices IMT1 involving all the six traits, IMT5 and IMT6 incorporating five traits were found to be the most desirable. The expected genetic gain per generation due to IMT1, IMT5 and IMT6 were 51.7208, 51.7189 and 50.3321g in egg mass; 1.2616, 1.1274 and 1.0747 eggs in egg production; -0.0278, 0.0274 and 0.0212g in egg weight; -0.3030, -0.3040 and -0.2901 days in ASM; 4.2878, 4.3077 and 4.1016g in BW20 and 2.5884, 2.6132 and 2.2705g in BW40, respectively. The corresponding values for aggregate genetic gain (ΔH), accuracy of indices (RIH) and relative efficiencies due to use of these indices of choice were 51.7208, 51.7189 and 50.3321 units; 0.3043,0.3043 and 0.2961 and 100, 99.9996 and 97.3150 percent, respectively. Based on estimates of genetic cost of restriction of different traits, the egg mass had the highest contribution followed by egg weight, egg production, BW20, BW40 and age at sexual maturity.