This study was conducted to determine the effects of supplementing threonine (Thr) at different levels in the diets on growth performance and immune responses of broiler chickens challenged with infectious bursal disease (IBD) and also to estimate Thr requirement based on different response criterion. A total of 300 one-day-old male broiler chicks were assigned to one of the six dietary treatments. Chickens were fed eight graded levels of Thr: 0.60, 0.67, 0.74, 0.81, 0.88 or 0.95% from day 21 to 42 of age. On day 28, all birds were challenged with a commercial live-IBDV vaccine. Body weight gain (BWG), feed conversion ratio (FCR) and carcass characterisation (breast, thigh and fat pad percentage) were significantly influenced by Thr levels. Increasing advisable level up to 0.81% of the diet resulted in significant improvement in the FCR and BWG. Thr supplementation had great effects on the antibody titer against IBD; the broilers receiving the Thr levels of higher than National Research Council (NRC) recommendation have a higher IBD antibody titer than those that received lower levels of Thr. The highest (0.822490.0211) and the lowest (0.724090.0140) were estimated with straight broken-line analysis for immune response (14 days post-challenge) and breast weight, respectively. The results obtained in the present study indicated that Thr requirements of broiler based on the recommendation of NRC are not sufficient to meet the requirement of the new commercial broiler companies under stress and non-hygienic conditions. The best level of Thr based on the current study was 0.81% for support growth performance and immune function.
The aim of this study was to determine the effects of supplementing Lysine (Lys) at on growth performance and immune responses of broiler chickens challenged with infectious bursal disease (IBD) and estimation of Lys requirement based on different response criterions. A total of 400-day-old male broiler chicks were assigned to eight dietary treatments. Chickens were fed by eight graded levels of Lys (0.8 National Research Council (NRC) (0.75% of diet), 0.9 NRC (0.85% of diet), NRC (0.94 of diet), 1.1 NRC (1.03% of diet), 1.2 NRC (1.13% of diet), 1.3 NRC (1.22% of diet), 1.5 NRC (1.41% of diet) and 1.8 NRC (1.69% of diet)) from day 21 to 42 of age. On day 28, all birds were challenged with a commercial live-IBDV vaccine. Body weight gains (BWG), feed conversion ratio (FCR) and carcass characterization (breast, thigh and fat pad percentage) were significantly influenced by dietary Lys levels. With increasing Lys level up to 1.22% of diet, performance improved significantly and with higher than this level decreased. Antibody titre against IBD was influenced by Lys levels. On 7 and 14 days after IBD challenge, antibody titre against IBD of broilers that receive diet that contain Lys higher than NRC recommendation wwas significantly higher than those receive lower level and the highest antibody level found in 1.22% Lys in diet. The highest (1.251990.0441) and the lowest (1.040890.11) Lys requirements with straightbroken line analysis were estimated for immune response and carcass efficiency percentage, respectively. The results obtained on the present study indicated that Lys requirements of broiler based on recommendation of NRC are not sufficient to meet the requirement of the new commercial poultry and commercial broiler companies under non-hygienic condition.
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