Comparative Performance of Chicken Breed Stocks in Diverse Rearing Environments

Abstract

Four genetic groups of chickens namely, a commercial hybrid broiler stock, a White Plymouth Rock, a Tanzanian local ecotype, and a cross between White Plymouth Rock and the local ecotype, were compared for performance  under two diverse rearing conditions. These consisted of total confinement plus balanced feeds, and day-time scavenging plus maize meal supplementation. Substantial differences were revealed  among  genetic  groups  for  body  weight gain, carcass weight, intestinal weight, and abdominal fat weight, in favour of the broiler stock, followed by the White  Plymouth  Rock  and  the  crossbred  group, which tended to rank either closely or similarly in most of  these attributes.  For most of the attributes considered in the study the differences between genetic groups were two to eight times larger under the intensive than under the extensive rearing system, thus reflecting the existence of important interactions between genetic groups and rearing systems. There was also evidence of the existence of substantial heterosis for most of the attributes considered, particularly within the extensive rearing system. It is concluded from these results that the apparent superiority of genetically improved stocks would not be available for exploitation in rural areas where the cost of nutritionally balanced composite feeds and other inputs are prohibitively high. Since grains are both abundant and cheap in rural areas the free range rearing system based on crossbred birds and grain supplementation would be most appropriate.