Effect of PFA supplementation on total antioxidant capacity and malondialdehyde in plasma of HS broilers. Total antioxidant capacity (A) and malondialdehyde (B) were measured in plasma. Main effects of diet, temperature, and the interaction are presented next to each graph. Data are presented as mean ± SEM (n = 6-8 birds/group). Different letters indicate significant difference at P < 0.05. Abbreviations: HS, heat stress; PFA, phytogenic feed additive; TE, Trolox Equivalents; TN, thermoneutral.