Effects of dietary levels of oregano oil on performance, physiologic and metabolic responses in broiler chickes.

To evaluate the effect of essential oils of oregano on performance, immune response and ascites in broiler chickens Arian, an experiment in a completely randomized design with a total of 500 broiler chicks, in 5 treatments, including the control diet, control diet + 100 mg/kg protexin, control diet + 150 mg/kg avilamysine and control diet + 200 and 400 mg/kg oregano oil with 4 replicates and 25 chicks were used.At age 42 days, from each experimental group randomly selected birds and to investigate performance parameter and ascites were slaughtered. At 35 days of age, to investigate the humeral immune response, the immune response against sheep red blood cells (SRBC) and blood factors, three birds of each treatment selected and from them were taken blood sample through vein under the wing. Body weight, feed conversion rate, feed intake, survival and production index in 42 days of age was not affected by treatment (p0.05). The relative weight of carcasses and parts of carcasses (except liver) was not affected by any of the treatments.Hematocrit, red blood cells and the ratio of right ventricular weight to total ventricular heart (RV/TV) was not affected by any of the treatments. Heterophile percent in treatment 200 mg / kg Oregano highest value (30.20) and no significant differences (p=0.062) with treatments 400 mg/kg Oregano and control group (respectively 27.00 and 26.80).no Significant differences (p0.05) in the percentage of lymphocytes was observed between the different treatments.Heterophil to lymphocyte ratio (H/L) in the group containing 200 mg/kg Oregano highest value (0.449) and a significant difference (p=0.077) with a 400 mg/kg Oregano and control group (respectively, 0.385 and 0.381). None of the treatments showed no significant effect on antibody titer against SRBC (p0.05). The results indicate no effect Oregano probiotics and antibiotics compared with the control group on cellular immunity in broilers.No significant differences were observed between the blood parameters (p0.05).Minimum number of Escherichia coli bacteria in the treatment of 400 mg per kg of oregano extract (6.152) and the highest number in the control treatment (7.574) was observed (p0.001). None of the treatments had no effect on lactobacilli counts (p0.05).Avilamycin lead to a significant reduction in the length, width and depth of the cripts in different parts of the small intestine (duodenum, jejunum and ileum) were. Most of cripts width in the jejunum and ileum sections of the small intestine in probiotic treatment was shown. Cripts depth ratio in the duodenum and jejunum sections treatments Avilamycin maximum value (respectively 8.47 and 7.64) and in the ileum in the probiotic treatment showed the highest value (7.67). Overall, the results indicate a significant effect (p0.001) Oregano on length, width and depth of the cript relative to the control sample. Key Words: oregano essential oil, Performance, immune response, ascites,Broilers.