GENETIC AND NON-GENETIC VARIATIONS OF BODY WEIGHT IN IRANIAN NATIVE FOWL AND THEIR CROSSES WITH EXOTIC BREEDS

This study was conducted on a stock of Iranian native fowl and their crosses with improved exotic breeds to evaluate their potential for body weight traits as well as to estimate genetic and phenotypic parameters for those traits, before initiating selection experiments. Four genetic groups were formed consisting of the native fowl and three crosses between native females with two different lines of broiler chickens and one parent stock of layer chickens. Two hatches placed 12 days apart and 4058 chicks were produced. In all genetic groups, body weight (BW) was recorded at 1, 39, 67, 95 and 123 days of age in the first hatch, and at 27, 83 and 111 days of age in the second hatch. Pooled heritability coefficients (sire component) of BW obtained at 1, 39, 67, 95 and 123 days of age in the first hatch and at 27, 83 and 111 days of age in the second hatch were estimated to be 0.48±0.08, 0.23±0.07,0.24±0.06,0.18±0.05,0.14±0.06,0.37±0.08, 0.20+0.05 and 0.31±0.09, respectively. From the estimates obtained in both hatches, heritability of BW tended to decrease with increasing age. Estimates of pooled genetic and phenotypic correlations of BW among early and late ages were highly significant (P<0.01) and positive. The sign of genetic correlations showed that correlations of BW taken at ages close together are higher than those separated by greater age. In native fowl and their crosses with meat-type chickens, there were relatively high heritability estimates of body weight at early ages (0.20 to 0.65) as well as their genetic correlations with subsequent ages (0.39 to 1.00). The results of this study indicated that selection on the basis of BW at early ages (27 or 39 days) can be used successfully to improve BW at subsequent ages (111 or 123 days).