Effect of dietary threonine level on productivity and carcass characteristics of indigenous Venda chickens

Abstract

Two experiments were conducted to determine the effect of dietary threonine level on productivity and carcass characteristics of indigenous Venda chickens. In each experiment the diets were isocaloric and isonitrogenous but with different dietary threonine levels. A complete randomized design was used in both experiments, the grower (1-49 days old unsexed Venda chickens) and finisher (50-91 days old female chickens) phases. The grower diets contained 4 (CT4), 5 (CT5), 6 (CT6), 7 (CT7) and 8 (CT8) g of threonine/kg DM, while similar diets were used for the finisher phase but designated (FT4), (FT5), (FT6), (FT7) and (FT8), respectively. A quadratic equation was used to determine threonine levels for optimal productivity. Dietary threonine level had significant effect (P>0.05) on feed intake, growth rate, FCR, live weight, ME intake and N-retention of unsexed and female Venda chickens. Feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and N-retention of unsexed and female Venda chickens were optimized at different dietary threonine levels. Dietary threonine level had no effect (P>0.05) on pH of crop, proventriculus, gizzard, small intestine, large intestine and caecum contents of female Venda chickens. Dietary threonine requirements for optimal productivity decreased as Venda chickens grew older. Dietary threonine levels for optimal productivity will depend on the particular variable in question. These findings have a lot of implications on ration formulation for slow-growing Venda chickens