Estimation of genetic parameters under optimal and suboptimal environments for body weight in chicken using a diallel mating system

Abstract

A 2 x 2 x 2N confounded diallel mating design (2 series, 2 males, N females per male per series) was used to obtain estimates of the genetic parameters in body weight traits in a noninbred population of New Hampshire chickens grown on 18% and 24% protein rations. Individual selection also was applied to evaluate the reliability of the genetic parameters obtained under each protein level. The analysis showed an extremely large contribution of series effects to the total variation in the traits which was attributed to the environmental influences from one series to the other and to the maternal environment. The component of variance due to series x male interaction was found to be small or zero under the 24% protein ration. An optimal environment may have given certain genotypes a greater opportunity to adapt to the environment. The higher estimates of the component of variance of series x female interaction for one-day body weight suggests the influence of maternal effects from one series to the other and from one dam to the other. Generally, estimates for the component of variance of male effects were higher under the 18% protein ration than under the 24% protein ration. Conversely, the component of variance of female effects showed higher values under the 24% protein ration than under 18% protein ration for most of the traits considered. ...