Antioxidant enzyme activities, plasma hormone levels and serum metabolites of finishing broiler chickens reared under high ambient temperature and fed lemon and orange peel extracts and Curcuma xanthorrhiza essential oil

The negative effects of high ambient temperature during some months of the year on poultry production have been of great concern in many countries. Dietary modifications are among the most practical ways to alleviate the effects of high temperature. Possible effects of dietary supplementation with 200 or 400mg/kg feed of lemon peel extract (LPE), orange peel extract (OPE) and Curcuma xanthorrhiza essential oil (CXEO) under hot conditions (34 degrees C with 50% relative humidity for 5h daily starting from day 28 until day 38 of age) on blood antioxidant enzyme activities, biochemical parameters and antibody titres of broiler chickens were investigated. All extracts are rich in phenolic compounds and highly available. Compared to control, supplementation with OPE at 400mg/kg and CXEO significantly increased erythrocyte glutathione peroxidase and superoxide dismutase activity, plasma growth hormone concentrations and serum phosphorus, total protein and chloride concentrations and decreased serum low-density lipoprotein and cholesterol concentrations in chickens at 38days of age. Regarding antibody titres, CXEO supplementation at 400mg/kg caused a significant increase in bronchitis antibody titres. Supplementation with LPE and OPE gave more inconsistent results. Most interesting, 400mg/kg LPE significantly increased 3,5,3-triiodothyronine and GH concentration as compared to the control. In conclusion, the herbal extracts tested in this study, in particular CXEO at 400mg/kg, may relieve some of the changes in blood composition induced by increased ambient temperatures.