Enhancing effect of oregano essential oil and Bacillus subtilis on broiler immune function, intestinal morphology and growth performance

The present study evaluated the effect of two categories of feed additives on chicken performance through immunological and intestinal histo-morphometric measurements. A total of 150 one-day-old male broiler chicks (Cobb) were randomly assigned to three groups. Group I received a non-supplemented basal diet. While groups II and III were treated with a basal diet supplemented with oregano essential oil (OEO) and Bacillus subtilis, respectively, in water for 28 days. Blood samples were taken at 6, 18 and 28 days for hematological analysis, phagocytosis, lymphocyte proliferation and measuring antibody responses. Additionally, growth performance indices were recorded weekly. The results showed that groups supplemented with OEO and B. subtilis improved growth performance expressed by a significant increase in weight gain (P < 0.05), with a significant reduction (P < 0.05) in feed conversion ratio (FCR). Hematological findings indicated a significant increase in blood parameters as well as a significant increase in phagocytic % & phagocytic index at all time points with a greater probiotic effect. On the other hand, OEO produced a significant increase in lymphocyte proliferation at 18 & 28 days. Humoral immunity revealed a significant increase in serum antibody titer phytobiotic & probiotic-fed groups at time points of 18 & 28 days with a superior phytobiotic effect. The histological examination showed a significant increase in villi length, villi width, crypt depth & V/C ratio. In conclusion, these results indicated positive effects of B. subtilis & OEO on both growth and immunity and could be considered effective alternatives to the antibiotic.