Positive Impact of Oregano Essential Oil on Growth Performance, Humoral Immune Responses and Chicken Interferon Alpha Signalling Pathway in Broilers

Supplementation of the herbal oils in poultry nutrition is considered an alternative and complementary approach to the conventional control viral strategies in poultry industry. Their use is associated with remarkable improvement in both bird performance and immunity. In the current study, one hundred twenty broiler chickens were allocated into four equal groups. Three groups (group B, C and D) were vaccinated with inactivated avian influenza and live LaSota vaccine and one group (group A) was left as a control non vaccinated group. Two groups, C and D, were orally treated with 0.005 and 0.01% Oregano essential oil (OEO) respectively. Oral supplementation with a higher dose exerts improvement in the bird performance parameters in the early period of bird life and up to 21 days of age. Positive regulation of both NDV and AIV-HI specific antibody titers was existed when the birds were supplemented with the oil together with both NDV and AI vaccination, especially in case of the higher dose. Study of the effect of the OEO on chicken interferon–alpha signalling pathway components post NDV vaccination using quantitative real-time PCR (qRT-PCR) revealed no obvious positive immunomodulatory effect on Myxovirus resistance 1 (Mx1) transcripts level except at 29 days of age. On the other hand, a dose dependent up-regulation in both IFN regulatory factor 7 (IRF-7) and interferon-alpha RNA levels was observed. Both doses of OEO could protect the birds from nervous manifestation resulting from challenge with vvNDV. In conclusion, oral supplementation with OEO has beneficial effects on bird performance as well as humoral and innate immune responses.