Estimation of genetic parameters and construction of multitrait selection indices in Japanese quails

The data from 206 Black and 205 Brown Japanese quails pedigreed by 33 and 40 sires, respectively were analyzed for body weight at 4-weeks of age (BW4), Age at first egg (AFE), egg production up to 12, 16 and 20 weeks of age (EP12, EP16 and EP20) for the effects of strain, generation and hatch. The effects of strain, generation and hatch were significant on all the traits under study, except for the effect of hatch on EP20. The overall least squares means for BW4, AFE, EP12, EP16 and EP20 were 191.77±0.85 g, 57.48±0.32 days, 18.02±0.31, 35.18±0.45 and 53.31±0.53 eggs, respectively. The heritability estimates for the above traits in Black strain were 0.42±0.15, 0.38±0.11, 0.52 ±0.10, 0.45±0.14 and 0.64±0.15, respectively and the corresponding values for brown strain were 0.34±0.09, 0.41±0.13, 0.56±0.15, 0.64±0.12 and 0.58±0.13. The genetic and phenotypic association between BW4 and AFE was negative in direction. Genetic association among BW4 and various EP traits were positive in direction in both the strains while negative association was observed for same set of traits at phenotypic level. The genetic and phenotypic correlations among AFE and EP traits were negative in direction, while positive association was observed among EP traits at both phenotypic and genetic level. A total of seven indices incorporating five traits were constructed and their efficiencies were compared. Index I₍₂₎ in Black and index I₍₄₎ in Brown strains were adjudged to be the best indices based on R_IH values. [I₂(Black) = 0.1176 (BW4) + 0.0864 (AFE) + 0.1562 (EP16); I₄(Brown) = 0.2072 (BW4) + 0.0528 (AFE)] and IH2 4 indicated the scope for simultaneous improvement of negatively correlated traits like body weights, age at first egg and egg production.