Expected and realized correlated responses in egg number of crossbreds and purebreds in egg type chicken
NEELAM SINGH, R.P.SINGH AND B.S. MALIK
Department Of Animal Breeding, College of Animal Science
Chaudhary Charan Singh Haryana Agricultural University
The data on performance traits of the pullets of two purebred strains (H & C) and their reciprocal crosses raised in multiple hatches over six generations (1994-2000) of crossbred selection program were analyzed. Selection of male and female breeders of purebred strains was done to improve the egg number upto 40 weeks of age of crossbred pullets produced on crossing the selected parents of opposite sex of the two strains. The criterion of selection for female was an index incorporating purebred individual's own egg number and egg number of its crossbred half sisters, while the male breeders were selected based on the egg performance of their crossbred half sisters only.
The results revealed that generation wise expected total response in egg number for crossbreds was 4.385, 5.766, 4.650, 3.967, 3.160 and 4.917 eggs respectively. Wide discrepancies between expected and realized direct responses were observed in G2, G4 and G6 generations. Such discrepancies mainly for the egg number may be accounted for non-availability of balanced feed during the laying period and also due to outbreak of Gumboro disease during that particular period/generation. Because of this, the pullets of that generation could not express their genetic potentiality for the productivity which they possess otherwise. Response in egg number of purebreds was expected to be positive (2.922, 0.209, 0.028, 0.037) in first four generation and negative (-0.024 and -0.021) in G5 and G6 generations. However, the realized responses in egg number of purebreds ranged from -16.14 to 11.66 over the six generations. Direct responses in egg number of purebreds declined in later generations which may be attributed to decline in additive genetic variance rather than other factors.