Due to their high metabolic rate, lactating sows are particularly susceptible to heat stress. Exposure to high temperatures increases the risk of oxidative stress, leading to cellular and tissue damage, which negatively impacts performance and health. Literature suggests that dietary supplementation with multiple antioxidant ingredients is more efficient than using a single one in alleviating the negative impacts of heat stress. As Europe had recently experienced increasingly hot summers, a study performed in the summer of 2023 compared the performance of lactating sows fed a diet including either a standard trace-mineral and vitamin premix (treatment C) or one enriched with additional antioxidants (treatment A). Accordingly, the premix A supplied (/kg feed) 245 mg of vitamin E (vs. 45 mg with premix C), 200 mg of vitamin C (vs. 0 mg with C), 1000 mg of betaine (vs. 0 mg with C), 25 mg of superoxide dismutase (vs. 0 mg with C), 0.35 mg of Se (0.20 mg from selenite and 0.15 mg from selenized-yeast vs. 0.25 mg from selenite with C). Other trace-minerals and vitamins were supplied at the same level in both premixes. Four batches of 24 Large White x Landrace sows were studied from July to October. Within each batch, pairs (replicates) of two sows were formed based on their parity, backfat thickness (BT) and body weight (BW) and then assigned to treatments. Data from 44 pairs of sows were collected. No significant effect of the treatment was observed on sows average feed intake (C: 5.61 vs. A: 5.38 kg/d, P = 0.59), BW change (C: -39 vs. A: -42 kg, P = 0.27) or BT change (C: -4.8 vs. A: -4.9 mm, P = 0.66), or litter ADG (C: 2.95 vs. A: 2.94 kg/d, P = 0.86). As hourly ambient temperature always remained above 25°C but rarely exceeded 30°C, hot conditions were likely too mild to greatly influence the oxidative stress status of sows thereby limiting the possibility of demonstrating a significant impact of antioxidants. This study is a part of the Fermadapt program funded by Région Bretagne.