Genetic analysis of part term egg production in a colored broiler dam line

Heritabilities and correlations were estimated among part term egg production upto 40 and 52 weeks of age and the constituting part records in PB2 strain of a colored broiler dam line under long term selection for egg production upto 40 weeks of age. The heritabilities of part term egg production upto 40 and 52 weeks of age were 0.114±0.07 and 0.205±0.03, respectively indicating higher estimates with extended part term production. The estimates for 28-day independent part records from 25–28, 29–32, 32–36 and 37–40 weeks of age were 0.280±0.10, 0.141±0.08, 0.154±0.08 and 0.123±0.08, respectively and those for cumulative part records at the end of 28, 32 and 36 weeks of age were 0.184±0.08, 0.154±0.08 and 0.151±0.08, respectively depicting a declining trend as the age of the birds advanced or as the duration of part record increased.

The phenotypic and genetic associations between part term egg productions at 40 and 52 weeks of age were positive, high and significant (P<0.05). The phenotypic associations of independent and cumulative part records with part term production at 40 and 52 weeks of age were also positive and medium to high ranging from 0.443 to 0.740 and 0.815 to 0.966 respectively. The corresponding genetic correlations were also positive and high ranging from 0.586 to 0.817 and 0.672 to 0.961, the intensity of which increased linearly with the length of the part record. Thus it may be inferred that egg production during initial periods (25 to 36 weeks of age) exercised a strong genetic and phenotypic influence on future egg production suggesting that sufficient genetic scope existed for the improvement of part term production through selection for early part records.