Abstract. The results of this study constitute a part of a project aiming at developing a cross-breed suitable for an extensive rearing system, utilising local biodiversity. Hybrids from mating a commercial broiler's male component (C) with Green-legged Partridgenous (GP) or Sussex (Sx) hens were compared with Cobb broilers. The study included 720 chickens of 3 genetic groups. Up to the third week of age, all birds were fed with balanced mixtures recommended for broiler chickens. From the fourth week, the mixture was weekly reduced by 10 % for the birds kept extensively (E). The deducted part was replaced with wheat bran, and from the seventh week with wheat. E groups had access to runs and received green fodder. Birds were slaughtered in 12th week of life. Carcass yield, giblets and proportion of carcass elements were estimated along with meat traits. The body weight at the 6th, 9th, 12th week of rearing and dissection results indicated a good suitability of Cobb chickens for an extensive rearing system. Hybrids were characterised by a considerably smaller proportion of breast muscle and slightly bigger of thighs and drumsticks, compared with Cobb, which could result from their greater motor activity. Results obtained by C × Sx and C × GP chickens, such as final body weight, proportions of abdominal fat and carcass elements, and appropriate value of meat traits, point at the usefulness of these hybrids as a meat-type chicken under extensive housing conditions. Darker colour of chicken meat, derived from C cocks and Sx or GP hens crossbred, can constitute an indicator for their carcasses' identification on the market.
The influence of oxytetracycline and vita-stress supplement on the productive performance of broiler chickens in the semi-arid zone of Nigeria
