Effects of olive (Olea europaea L.) leaf extract and sesame (Sesamum indicum L.) oil on performance, nutrient digestibility and antioxidant status of broiler chickens under heat stress

This study was conducted to investigate the synergy effects of adding sesame oil (SEO) and olive leaf extract (OLE) as sources of natural antioxidants to the diet on the performance, nutrient digestibility and antioxidant status of broiler chickens under heat stress condition. Three hundred Ross male broilers were randomly distributed to 30 experimental units and 6 dietary treatments (5 replicates with 10 birds in each). The completely randomized design with factorial arrangement 3×2 with 3 levels of OLE (0, 200 and 400 mg/kg of diet) and 2 types of vegetable oil [crude corn oil (CRO) and SEO] were used. The experimental diets included: a corn soybean meal based diet with added CRO and without OLE supplementation, a basal diet with SEO and without OLE supplementation, a basal diet with added CRO and 200 mg/kg OLE supplementation, a basal diet with added SEO and 200 mg/kg OLE supplementation, a basal diet with added CRO and 400 mg/kg OLE supplementation and a basal diet with added SEO and 400 mg/kg OLE supplementation. Heat stress was applied for 6 h from 29 to 42 days. Feed intake, feed conversion ratio and daily gain of broiler chickens were not significantly affected by treatments. The inclusion of SEO and/or OLE up to 200 mg to the diet significantly increased the relative weight of Bursa of Fabricius. The use of OLE and SEO in diet did not have any significant effect on blood antioxidant parameters. It can be concluded that the use of OLE up to 200 mg in terms of heat stress, improves nutrient digestibility in broiler diets, but no significant effect on improving the performance of birds.