Effect of Excess Dietary Tryptophan on Performance, Plasma Hormone Levels and Immune Function of Broiler Chickens Reared Under Hot and Humid Summer Conditions

The effects of L-Tryptophan supplementation on growth performance, hormone levels, and immune function of heat-stressed broiler chickens were investigated. For ۴۲ days, ۴۸۰ male chicks were exposed to repeated cycles of hot temperatures and fed one of four diets: a basic diet (control group) or the same diet with extra L-Tryptophan added at three different levels (۰.۲, ۰.۴, and ۰.۶ g/kg diet). L-tryptophan supplementation did not significantly improve overall growth performance under heat stress. However, broilers fed ۰.۲ and ۰.۶ g/kg L-Tryptophan had a better feed conversion ratio at ۱۰ days old. There were no significant differences in white blood cell counts. Interestingly, L-tryptophan supplementation increased antibody production against Influenza and Newcastle disease viruses at ۱۴ days. Additionally, L-tryptophan influenced hormone levels, slightly decreasing growth hormone and increasing thyroxin at ۱۰ days, with further increases in triiodothyronine observed at ۲۴ and ۴۲ days. While L-tryptophan supplementation did not enhance overall growth performance under heat stress, it positively impacted blood parameters like thyroxin, triiodothyronine, and immune response against specific viruses.

کلیدواژه ها:

Heat stress ، Broiler chicken ، Growth hormone ، Thyroid hormone ، Immune response ، Tryptophan supplement