Abstract
One hundred and eighty one-day-old dual purpose chicks of mixed sex were used to investigate the effect of partial replacement of soybean protein by sunflower meal (SFM) without or with essential oil mixture (EOM) supplementation on growth performance, immune response, carcass characteristics and intestinal histopathology of broiler chickens. The birds were divided into 6 groups of a completely randomized design of 3 levels of sunflower meal (0, 15 and 30 %) as a substitute for soybean meal with or without essential oil mixture supplementation. The basal diets were formulated based on corn and soybean meal to meet the nutrient requirements of broiler chickens. Broilers fed on diets containing sunflower meal had a good growth performance comparable to those fed on diets without sunflower meal. Moreover, the replacement of soybean protein by SFM with EOM supplementation improved phagocytic activity, phagocytic index and antibody titer against Newcastle disease vaccine at 21th, 35th and 49th of broiler age when compared with groups fed on the same diets without EOM supplementation. SFM containing diets significantly (P≤0.05) increased total bacterial counts compared with control group fed on corn - soybean based diet. However, it was observed that 0%, 15% or 30% of soybean protein replacement by SFM with EOM supplementation had no significant effect on intestinal total bacterial counts compared with groups fed on the same diet without EOM supplementation. Moreover, 15% of soybean protein replacement by SFM significantly (P≤0.05) increased ileum villi length and non-significantly improved crypt depth and width when compared with control group. On the other hand, 30% of soybean protein replacement by SFM had no significant effect on ileum villi length while, significantly (P≤0.05) reduced ileum crypt depth and width compared with control. In addition to that, it was observed that 0.0, 15% or 30% of soybean protein replacement by SFM with EOM supplementation improved ileum villi length, crypt depth and width compared with broiler chicks group fed on the same diet without EOM supplementation. , it can be concluded that sunflower meal without or with essential oil mixture supplementation could be successfully incorporated in broiler diets as a substitute of soybean protein.

Key words: Broiler chickens – sunflower meal – Essential oil - Growth performance – Immune response – Intestinal villi.