Gene expression of heat shock protein 70 and antioxidant enzymes, oxidative status, and meat oxidative stability of cyclically heat-challenged finishing broilers fed Origanum compactum and Curcuma xanthorrhiza essential oils

Heat stress in poultry is a serious prob- lem in many countries and has been associated with oxidative stress. Hence, nutritional interventions with antioxidants might be beneficial. Therefore, the effects of dietary Curcuma xanthorrhiza (CX) and Origanum compactum (OC) essential oils on mRNA levels of heat shock protein 70 and antioxidant enzymes, oxidative status, and meat oxidative stability of heat-challenged broilers were studied. Starting on d 25 of age, a control diet and 4 diets containing 200 or 400 mg/kg feed of CX or OC (CX200, CX400, OC200, OC400 diets) were fed to 3 pen replicates of 20 Ross 308 chickens each. From d 28 of age on, the temperature was increased from 22 to 34°C with 50% RH for 5 h daily during 2 wk. Dietary CX or OC did not affect zootechnical performance. Feeding CX400 and both levels of OC in- creased the a* value in stored breast meat (P < 0.05), and OC diets tended to decrease the thiobarbituric acid reactive substances values in fresh breast meat (P = 0.061). Compared with control, at d 31, feeding CX400 and OC400 reduced mRNA levels of heat shock protein 70 and increased mRNA levels of catalase in kidney and liver (P < 0.05). The mRNA levels of superox- ide dismutase were increased at d 31 on the OC400 diet in kidney and on the CX400 diet in heart (P < 0.05). In heart, at d 31, both dietary levels of CX and OC200 resulted in higher glutathione peroxidase activ- ity (P < 0.05). Feeding CX400 increased superoxide dismutase activity in liver, kidney, and heart at d 31 (P < 0.05). Catalase activity was increased in the CX200 and OC400 groups at d 42 (P < 0.05). Feeding CX at both levels and OC200 decreased plasma malondialde- hyde concentrations at d 42 (P < 0.05). In conclusion, dietary essential oils rich in simple phenolic compounds offer potential for improving the antioxidant defense against heat stress-induced changes.