The present study was conducted to determine the effects of essential oil mix (orange peel oil + bay leaf oil + thyme oil) added into basic mixed feed on performance parameters, carcass traits, some blood parameters and antioxidant parameters in quails (Cotunix coturnix Japonica) exposed to heat stress. Totally 96 quails from both genders were used including 32 animals in each group in the study. Each group were divided into 4 subgroups including 8 quails in each one. The animals were exposed to 34±2ºC of heat stress (28 days) for 8 hours (9.00-17.00) per day. The study groups were as follows; Control group which was exposed to heat stress and received basic mixed feed only with zeolite, Zeolite group which was exposed to heat stress and received 200 ppm dose of essential oil mixture stabilized with zeolite added into mixed feed, and Capsule group which was exposed to heat stress and received the mixed feed added with 200 ppm dose of essential oil mixture stabilized by microcapsulation. Among the research groups, the highest live weight (43. day), live weight gain (15-43. days), and feed conversion ratio were obtained in the capsule group (P<0.05). Hot carcass weight and carcass performance were found higher in groups receiving feed with essential oil mixture than control group (P<0.05). In the trial, it was determined that while the lowest levels of glucose (P<0.01), uric acid, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were observed in capsule group (P<0.05), control group had the highest cholesterol and triglyceride levels (P<0.05). While the lowest malondialdehyde (MDA) levels of liver (P<0.05) and heart (P<0.001) were determined in capsule group, the highest glutathione peroxidase (GSH-Px) levels of liver (P<0.01) and heart (P<0.05) were also observed in capsule group.

As a result; it was concluded that the efficiency of microcapsulation method used for stabilization of essential oils was higher than zeolite absorption method and the use of essential oils in stability processes can increase the performance to be obtained from animals.