Abstract
This study evaluated the effects of dietary methionine and turmeric oil, both individually and in combination, on antibody response, carcass cut percentages, and economic return percentages in broiler chickens vaccinated against Newcastle Disease (Genotype VII) and avian influenza (H5). Two hundred one-day-old male Hubbard chicks were divided into four dietary groups (with 5 replicates per group and 10 birds per replicate) and treated for 35 days as follows: C group: fed a basal diet; M group: fed a basal diet supplemented with 1 g DL-Methionine/kg; T group: fed a basal diet supplemented with 200 mg turmeric oil/kg; M+T group: fed a basal diet supplemented with 1.0 g DL-Methionine plus 200 mg turmeric oil/kg. Vaccinations were given on days 1, 9, and 19, and antibody titers were evaluated weekly until the completion of the experiment with the hemagglutination inhibition test. The weight of immunological organs and the mRNA expression of Interleukin 6 (IL-6) and Interleukin 8 (IL-8) were assessed using qRT-PCR at the end of the experiment. Methionine and turmeric oil significantly boosted spleen weight as compared to the control group (p<0.05). The results revealed that the combination of (M+T) had a more concomitant effect on the relative weight of both the bursa and the thymus than the other treatments. However, M or T improved spleen and bursa weights and increased breast yield and breast economic return (P < 0.05). The M group, alone or combined (M+T), significantly improved Newcastle disease and avian influenza vaccine titers (p<0.05) compared to the T group alone. Furthermore, dietary M or T supplementation elevated IL-6 and IL-8 expressions, whereas the (M+T) group demonstrated the greatest upregulation suggesting a potential nutritional regulation of cytokine gene expression. In conclusion, administering methionine alone or in combination with turmeric oil revealed a relative advantage in achieving immune response balance and stability over various trial periods, and improving carcass cut percentages and their economic return percentages. Furthermore, turmeric oil alone modulated cytokine expression without enhancing antibody titers. These findings serve as a cornerstone for future research into the effects of combining methionine and turmeric oil in broiler chicken diets in the lab and in the field to combat viral diseases that threaten the broiler industry, such as avian influenza and Newcastle disease.

Key words: Immune response, Avian influenza, Newcastle Disease (ND), Returns, Cytokines