Dietary oregano essential oil alleviates experimentally induced coccidiosis in broilers

• We study effects of oregano essential oil on growth performance and coccidiosis prevention in mild challenged broilers.
• Two dietary levels (300 and 500 ppm) of oregano oil were compared to Diclazuril as a chemical anticoccidial drug in challenged broilers with sporulated oocysts of Eimeria.
• Oregano oil at either supplementation rate improved performance.
• Challenged broilers fed 500 ppm oregano oil or Diclazuril displayed lower coccidiosis lesions scores.
• Oregano oil at the dose of 500 ppm in diet has beneficial effects on coccidiosis prevention in broilers.

An experiment was conducted to determine the effects of oregano essential oil on growth performance and coccidiosis prevention in mild challenged broilers. A total of 250 1-d-old chicks were used in a completely randomized design with 5 treatments and 5 replicates with 10 birds in each replication. Experimental treatments included: (1) negative control (NC; unchallenged), (2) positive control (PC; challenged with sporulated oocysts of Eimeria), (3) PC fed 200 ppm Diclazuril in diet, (4) PC fed 300 ppm oregano oil in diet, and (5) PC fed 500 ppm oregano oil in diet. At 22 d of age, all the experimental groups except for NC were challenged with 50-fold dose of Livacox T as a trivalent live attenuated coccidiosis vaccine. On d 28, two birds were slaughtered and intestinal coccidiosis lesions were scored 0–4. Moreover, dropping was scored in the scale of 0–3, and oocysts per gram feces (OPG) were measured. Oregano oil at either supplementation rate increased body weight gain (P = 0.039) and improved feed conversion ratio (P = 0.010) from d 22 to 28, when compared with PC group. Using 500 ppm oregano oil in challenged broilers diet increased European efficiency factor than PC group (P = 0.020). Moreover, challenged broilers fed 500 ppm oregano oil or Diclazuril in diets displayed lower coccidiosis lesions scores in upper (P = 0.003) and middle (P = 0.018) regions of intestine than PC group, with the effect being similar to unchallenged birds. In general, challenged birds fed 500 ppm oregano oil or Diclazuril in diets had lower OPG (P = 0.001), dropping scores (P = 0.001), litter scores (P = 0.001), and pH of litter (P = 0.001) than PC group. It could be concluded that supplementation of oregano oil at the dose of 500 ppm in diet may have beneficial effect on prevention of coccidiosis in broilers.