Department of Animal Breeding, C.C.S. Haryana Agriculture University, Hisar - 125 004 (Haryana).
1 Dept. of Animal Science, GBPUA&T, Pantnagar - 263145.
Genetic variability for growth and reproduction traits on 2439 pullets of a broiler dam line was estimated over five generations. Initially the cockerels were selected on the basis of their half sisters. The pullets in the first stage were selected on the basis of their sire family means for egg number and finally on an index combining 6 weeks body weight, egg number and egg weight. The regression of generations means of body weight at 6,20 and 4o-weeks age, age at first egg, egg number to 40 weeks age and egg weight at 32 weeks age on generation number were -0.007±0.015, -0.006±0.001, -0.004±0.001, 0.066±0.115, 0.168±0.155 and -0.270±0.015, respectively. The heritability estimates for these traits ranged from 0.02±0.20 to 0.59±0.14, 0.08±0.07 to 0.64±0.21, 0.001±0.06 to 0.59±0.21, 0.17±0.09 to 0.49±0.19, 0.11±0.08 to 0.39±0.18 and 0.35±0.13 to 0.52±0.19 respectively. The corresponding regression of heritability estimates on generation number for these traits were -0.095±0.022, -0.1l4±0.052, -0.069±0.070, -0.072±0.024, -0.017±0.047 and -0.047±0.10. In general, the heritability estimates showed declining trend over generations.
Body weight, age at first egg, egg number, egg weight and regression
