Oregano (<i>Origanum vulgare</i> L.) Essential Oil Feed Supplement Protected Broilers Chickens against <i>Clostridium perfringens</i> Induced Necrotic Enteritis

Oregano (Origanum vulgare L.) is a well-known traditional medicine and a cooking spice. Recent practice has also applied the essential oil from oregano (OEO) in poultry due to its great potential for an antibiotic alternative. Our objective was to evaluate the potential effects of OEO (with carvacrol and thymol as the main active ingredient) on preventing necrotic enteritis (NE) caused by Clostridium perfringens (Cp) in chickens. In the feeding trial, a total of 450 one-day-old commercial Arbor Acres broilers were randomly assigned in 5 experimental groups during a 26-day production period (d19 to d 26 was the Cp challenge stage), and each group consisted of 6 replicate pens (15 birds each pen). All treatments were: basal diet (control group); basal diet and Cp challenge (model group); Cp challenge and 10 mg/kg enramycin (positive control group); Cp challenge and 200 mg/kg OEO product (OEO low dosage group, OEOL); Cp challenge and 300 mg/kg OEO product (OEO high dosage group, OEOH). OEO feed supplement at both dosages had significant effects on increasing the body weight gain (BWG) and reversing the dropped feed intake (FI) induced by Cp challenge. Histopathological changes in the ileums of broiler chickens with NE induced by Cp were alleviated by OEO, which was mutually confirmed by the intestinal lesion scores. Dosage did not influence the protective effect of OEO on intestinal lesion scores. Furthermore, OEO was found to have limited effects on tight junction-related gene expressions (Occludin and ZO-1). The broilers of the OEOL and OEOH groups significantly decreased the expression of TNF-α mRNA in the ileum and only the OEOH group was found to inhibit the IFN-γ expression of IFN- induced by Cp challenge. Finally, despite the fact that in vitro antibacterial effects by OEO were observed, considering its high minimum inhibitory concentration (MIC) value, we inferred that the protective effects by OEO against Cp challenge were not attributable to its direct antibacterial effects. We proposed OEO as a promising substitute for antibiotics against NE induced by Cp during poultry production