This study evaluated the effects of different feed additives on growth performance and heat stress mitigation in
broiler chickens. Three hundred 1-d-old Cobb broiler chicks were randomly allocated into five treatments, each
treatment contained six replicates (10 birds/replicate). Treatment 1 (-Control) was fed a basal diet (BD) under
thermo-neutral conditions between d 1 and 42 of age. Treatment 2 (+Control) also fed the BD under thermoneutral conditions from d 1 to 28 of age, followed by exposure to cyclic heat stress (HS; 36◦C between 0900
and 1700 h, then to 24◦C between 1700 and 0900 h daily) during the fifth week. During the fifth week,
Treatments 3, 4, and 5 underwent the same HS regime and fed the same BD containing 15g/kg of thyme oil (TO),
cinnamon oil (CO), and pomegranate oil (PO) from d 1 to 42, respectively. Compared to the thermoneutral
control, HS control exhibited lower ADFI, higher FCR, increased mortality rate, altered plasma biochemicals, and
reduced anti-oxidant capacity. Broilers supplemented with PO showed a 14.4 % increase in final BW and a 25.8
% in ADG during recovery period. FCR was improved by 16.9 %, and mortality dropped to 6 % compared to 10 %
in the HS control, suggesting reduced losses under heat stress. TO and CO treatments also showed beneficial
effects compared to the HS control group. The supplemented feed additives decreased plasma cholesterol, triglycerides, and malondialdehyde content, while increasing plasma glutathione peroxidase activity and total
antioxidant capacity relative to the HS control. TO, CO, and PO treatments exhibited higher plasma superoxide
dismutase activity compared to the HS control. All supplemented treatments showed lower H/L ratio compared
to HS control (P < 0.05). The PO and TO treatments exhibited an increased jejunal villus/crypt ratio relative to
the control groups. In conclusion, supplementing broiler diets with PO, TO, and CO can alleviate heat stress
effects, improve growth performance, and potentially boost profitability for poultry farmers, with PO providing
the most significant benefits in both thermoneutral and heat stress conditions.