Determination of optimum methionine requirements of broiler chickens reared during the hot season under tropical environment

Abstract

Dietary amino acids in excess of the needs of broiler chickens may impair feed intake and growth rate. An experiment was conducted to determine the optimum dietary methionine requirement for broiler chickens reared during the hot season under tropical condition. A total of three hundred day old broiler chicks were used for the starter phase and two hundred and seventy chicks for the finisher phase. Each experiment had five treatment groups and three replicates per group. The  experimental diets were five with graded levels of supplemental methionine at: 0.15, 0.20, 0.25, 0.30 and 0.35 % to give total dietary methionine levels of 0.45, 0.50, 0.55, 0.60 and 0.65 % for the starter phase feeding trial. For the finisher phase feeding trials, supplemental methionine levels of 0.14, 0.19, 0.20, 0.25 and 0.30 % to give total dietary methionine levels of 0.40, 0.45, 0.50, 0.55 and 0.60 % were fed to the chicks. Each experiment lasted from 0 – 4 weeks for the starter phase and 5 – 8 weeks for the finisher phase. Results for the starter phase indicated significant (p<0.05) linear increases for total weight gain and average daily gain as the dietary levels of methionine increased. The birds fed 0.60 % methionine diet had the highest (p<0.05) final body weight, better feed conversion ratio and feed cost per kg weight gain. The results for the finisher phase show that birds fed 0.60 % methionine diet performed significantly (p<0.05) better in terms of the body weight gain, feed conversion ratio and feed cost/kg weight gain than those fed lower methionine levels in diets. It was concluded that the methionine requirement was 0.60 % for the starter diet. For the finisher phase, a linear increase in the body weight gain was observed up to the highest dietary level of methionine tested (0.60 %). Hence, the optimum dietary level of methionine may be above 0.60 %. Further studies will be necessary to establish higher doses of dietary methionine in broiler finisher reared under tropical climatic conditions.

Keywords: Dietary amino acid, Methionine diets, Broiler, Growth rate, Tropical environment, Feed conversion ratio, Feed cost per kg weight gain