Genetic study of Dandarawy chickens: I. Heritabilities and genetic correlations of body weight and weight gain

Abstract

Summary — Heritability values of body weight and weight gain at the ages of 1 d, and 4, 8, 12, and 16 wk were estimated from 57 half-sib families of a strain of the Egyptian breed Dandarawy representing 57 sires, 256 dams, and 1,605 offspring. Estimates were obtained for both of the sexes separately as well as for the two combined. The estimates of heritability ranged from 0.24 to 0.60 for males and females from sire components of variance, and 0.03 to 0.37 for males and females from dam components of variance. There were marked differences between heritability estimates from sire and dam components of variance and between males and females. The heritability estimates from sire components were generally higher than those from dam components, which indicated the importance of the additive genetic effect and possible sex-linked effects. It was also noticed that the environment had an effect on both body weight and weight gain which is reflected in heritability estimates from one age to another.The results showed that there were highly significant correlations between body weights from 4 to 16 wk of age. There were no correlations between hatch weight and weights at the other ages. This indicates that it is possible to consider the hatch weight as a trait completely separate from the other traits in males, females, and the sexes combined. The highly significant genetic and environmental correlations showed that both genetic and environmental factors had the same influences on body weight from 4 to 16 wk of age. There were absent estimates of the genetic correlations especially with the dam components of variance in males and females. The correlations between weight gains at different periods showed highly significant estimates up to 12 wk of age. These correlations reflect the importance of both genetic and environmental effects on weight gain at the different periods. Our results indicate that it is possible to select for body weight and weight gain at an early rather than a late (16 wk

Estimation of genetic parameters for body weight traits in squab pigeons

“…Estimates of r 9 between weight at hatch and weight at ages 2-4 wk were low and suggest that squab hatch weight is a poor indicator of later body weight. As pointed out by Abdellatif (1989), hatch weight must therefore be considered a separate trait. The relatively high heritability for 4 wk body weight, low heritabilities for weight at other ages, and the low or negative genetic correlations among weight gains for different periods could indicate that squabs are opportunistic growers having the genetic potential to make compensatory gains whenever conditions are favourable.…”