Estimation of Dietary Threonine requirement for starter period of broilers based on the Performance and Immune Responses Criterion

ABSTRACT:this study was conducted to determine the effects of supplementingThr onthe performance and immune responses of broiler chickens challenged with newcastell Disease (ND) and estimation of Thr requirement based on different response criterion. A total of 216one-day-old male broiler chicks were assigned tosix dietary treatments. Chickens were fed by six graded levels ofThr100%NRC(0.8),120%NRC(0.96),140%NRC(1.12),160%NRC(1.28),180%NRC(1.44),200%NRC(1.6).All birds were challenged with a commercial live-ND vaccine. Bodyweight gains (BWG), feed conversion ratio (FCR) and carcass characterization (breast, thigh and fat pad percentage) were significantly influenced by dietary Thrlevels. With increasing Thr level up to 1.12% of diet performance improved significantly and with higher than this level deceased. Antibody titeragainst ND was influenced by Thr levels. On 7 and 14 days after NDchallenge, antibody titer against ND of broilers that receive diet containThr higher than NRC recommendationwere significantly higher than that receive lower level and the highest antibody level find in 1.12% Thr in diet.The results obtained on the present study indicated that Thr requirements of broiler based on recommendation of NRC are not sufficient to meet therequirement of the new commercial poultry and commercial broiler companies under non-hygieniccondition.