This study aimed to evaluate the effects of betaine and an antioxidant complex on the growth performance of broiler chickens under heat stress conditions. The experiment was conducted with 360 one-day-old male Ross 308 broiler chicks, using a completely randomized design with six treatments and six replications. The treatments included: a basal diet without additives under normal temperature conditions (TNC), a basal diet without additives under heat stress conditions (HSC), a basal diet supplemented with betaine (Bet), a basal diet supplemented with an antioxidant complex containing vitamin E, vitamin C, and selenium (ECS), and a basal diet supplemented with both betaine and the antioxidant complex (Bet+ECS). The results indicated that the combined treatment (Bet+ECS) significantly increased average daily weight gain, average daily feed intake, and improved feed conversion ratio compared to the HSC group during both the 10–24 day and 0–42 day periods (P < 0.05). Overall, the Bet+ECS group showed performance comparable to the normal temperature control group (TNC). Additionally, the ECS and Bet treatments resulted in higher average daily weight gain compared to the HSC group (P < 0.05), though their performance was lower than that of the TNC group (P < 0.05). These findings suggest that the combination of betaine and antioxidants can effectively enhance growth performance, feed intake, and feed efficiency in broiler chickens under heat stress conditions.
