Indian Journal of Poultry Science

Heritabilities and correlations were estimated among certain growth and production traits in IWK strain of White Leghorn. The heritability of age at first egg was found to be very low (0.02) indicating that it is difficult to improve age at first egg through selection. The estimates of heritability for body weight and egg weight at various ages were moderate to high implying that there is sufficient scope for improvement of these traits. The heritabilities of egg production upto 40, 64 and 72 weeks of age were found to be 0.059±0.072, 0.108±0.077 and 0.590±0.176, respectively and the estimates increased along with the age suggesting that selection based on a longer production period will yield better results. The heritabilities of egg weight at 40 weeks (0.365) and 64 weeks (0.516) were higher than those at 28 and 52 weeks of age.

Hence, egg weight at 40 or 64 weeks may be considered for selection. The genetic correlation of age at first egg with body weight at 6, 10, 16, 20 and 40 weeks of age and egg production up to 64 and 72 weeks of age was negative while with egg weight at 28, 40 and 52 weeks of age, it was positive and high. The genetic, phenotypic and environmental correlations among body weights and egg weights at nearby ages were positive. The positive genetic correlation of early body weights at 4, 6 and 10 weeks with egg production up to 40 and 64 weeks indicated the importance of body weights at these ages for higher egg production. The genetic, phenotypic and environmental correlations between part period and annual egg production and between egg weights at various ages were mostly positive while the correlations between egg production and egg weights were negative. Thus, it may be inferred that simultaneous improvement of egg production and egg weight may be difficult and early body weights at 4, 6 and 10 weeks are important for higher egg production.