The use of oregano essential oil and enzyme mixture in corn-soybean meal based diets of broiler chicks

This study was conducted to investigate the effects of the dietary oregano essential oil (OEO) with or without enzyme (ENZY) supplementation on the growth performance, digestive enzymes' activity, nutrient digestibility, lipid metabolism and immune response of broilers until to 21 d. The diets were supplemented with: no OEO or ENZY, 1 g/kg of the ENZY, 250 mg/kg of the OEO, 250 mg/kg of the OEO plus 1 g/kg of the ENZY, 500 mg/kg of the OEO, 500 mg/kg of the OEO plus 1 g/kg of the ENZY. The OEO supplementation at the level of 250 mg/kg significantly increased body weight gain during d 7 to 14 and d 0 to 21 and improved feed conversion ratio during only d 7 and 14. Supplementation of OEO at the both levels also increased feed intake, on the other hand, worsened feed conversion ratio, during d 14 to 21. The dietary ENZY supplementation alone significantly improved the BWG and FCR only at the period of 0 and 7 d. The OEO supplementation at the both levels significantly increased amylase activity at d 7 and chymotrypsin activity at d 14, the relative weights of pancreas and B. fabricius of broilers at d 21. On the other hand, OEO only at the 250 mg/kg level or ENZY supplementation significantly improved the faecal crude protein digestibility compared to the unsupplemented diet. Serum IgG and IgM levels and the antibody titres to NDV were significantly increased by OEO supplementation at the both levels. No interaction between OEO and ENZY were observed for all parameters. As a result, it can be said that the OEO supplementation alone at 250 mg/kg to corn-soybean meal based diet was neccessary to significantly improve the BWG and FCR and antibody titres to NDV for the first weeks of broilers. The positive effect of OEO was pronounced during the starter phase.