EFFECT OF DIETARY TRYPTOPHAN LEVELS ON GROWTH PERFORMANCE OF BROILER CHICKENS REARED IN THE HOT SEASON UNDER TROPICAL ENVIRONMENT

Abstract

This study was conducted to evaluate the effect of dietary levels of tryptophan on growth performance of broiler chickens reared under tropical environment. At the starter phase, a total of two hundred and eighty five day old mixed sex Arbor Acres broiler chicks were randomly allotted to five dietary treatments with three replicates each having nineteen (19) chicks. At the finisher phase, two hundred and seventy broilers were also allotted to five dietary treatments with three replicates each having 18 broilers per replicate. The dietary tryptophan levels at the starter phase were 0.15, 0.19, 0.23, 0.27 and 0.31% respectively while the diets for the finisher phase contained 0.13, 0.17, 0.21, 0.25 and 0.29% dietary tryptophan respectively. All other nutrient levels were constant. The experiment was conducted at 0 to 28d (starter phase) and 33 to 56d (finisher phase). Growth performance traits including weight gain, feed intake and feed conversion ratio were recorded at the end of each week. The results for the starter phase showed that chicks fed diet containing 0.23%, 0.27% and 0.31% dietary tryptophan had similar results in term of the weight gain, average daily weight gain, feed intake and average daily feed intake. For the finisher phase, the birds fed 0.21%, 0.25% and 0.29% tryptophan diets also had similar results in terms of final weight, weight gain, feed intake and average daily feed intake. Our results suggest that supplemental tryptophan was sufficient to have significant (P<0.05) effect on broiler performance. However, polynomial regression analysis reveals that the optimum performances were reached at 0.24% and 0.21% dietary tryptophan for the starter and finisher phases respectively. Therefore, it can be concluded that dietary tryptophan requirements during the hot season for the starter and finisher phases were 0.24% and 0.21%, respectively.