| Popis: |
Heritability of growth traits was studied at 2, 10 and 20 weeks using 531 day-old unsexed crossbred chickens belonging to six genotypes. Heritability estimates were obtained from variance components of sire ( ), dam ( ) and sire plus dam ( ) by analysis of variance in a nested design. The heritability of body weight was high (0.43-0.66) in frizzle feathered x Isa Brown (FxIB), Isa Brown x frizzle feathered (IBxF), Isa Brown x normal feathered (IBxN) and normal feathered x Isa Brown (NxIB) at 10 and 20 weeks, but low to moderate (0.02-0.38) in Isa Brown x naked neck (IBxNa) and naked neck x Isa Brown (NaxIB) at all ages from different variance components. The heritability of shank length was high at weeks 2 (0.45) in NaxIB, 10 (0.53-0.90) in IBxF, IBxN and NaxIB and 20 (0.40 - 0.53) in IBxNa and IBxN from . The heritability of drumstick length (0.40 - 0.46), body girth (0.54 - 0.62), body width (0.50 - 0.81) and keel length (0.72 - 1.50) was also high from different variance components and ages. Body length was highly heritable only in IBxN (0.50) from at 20 weeks. Wing length was lowly to moderately heritable (0.01 - 0.36) at all ages of the genotypes. There was large additive genetic variance for most of the traits in different genotypes and ages. Rapid genetic improvement of growth can be made in these chickens by individual selection, especially using shank length of IBxN from sire lines between 10 and 20 weeks of age. |
