Effect of wheat-based diet supplementation with different levels of dried oregano leaves (Origanum vulgare L.) on performance, immune response, and blood metabolites of broiler chickens

The objective of the present study was to investigate the effects of dietary supplementation with different levels of dried oregano leaves (DOL) on growth performance, carcass traits, blood metabolites and immune response of broiler chickens fed wheat-based diet. One hundred sixty day-old female broiler chicks (Ross- 308) were used in a completely randomized design (CRD) with 4 treatments, 5 replicates, and 10 chicks each. The treatments included four levels of dietary supplementation of DOL (0, 0.4, 0.8, and 1.2%). The experiment lasted up to 42d of ages and performance indexes calculated during 1-18, 19-30, 31-42, and 1-42d of ages. With increasing in dietary DOL levels, feed intake (FI) during 19-30d of ages and feed conversion ratio (FCR) during 31-42 and 1-42d of ages were changed as a significant quadratic polynomial curve. Feed conversion ratio was the optimum in the birds fed the diet supplemented with 0.4% DOL. The dietary supplementation of DOL did not significantly affect on weight gain. As increased dietary DOL levels, the gastrointestinal intestinal tract (GIT) organs relative weight, blood serum triglyceride (TG) concentration linearly decreased, and carcass yield, humoral immune response to SRBC inoculation, thymus organ relative weight, and blood serum low-density lipoproteins (LDL) concentration decreased (P<0.05). This study revealed that wheat-based diets supplemented with 0.4% DOL can improve feed efficiency, carcass yield, and health status of broiler chickens.