This study sought to determine the impact of dietary supplementation with yeast β-glucan on the alleviation of heat stress (HS) in lactating sows during the summer. Thirty cross-bred sows (Landrace × Yorkshire) with an initial body weight of 216.2 ± 7 kg, an average parity of 3, and their litter were used in this study. Sows were randomly allotted to three treatments (10 sows per treatment). The treatments included the control group (CON), BG5 (supplemented with 0.05% β-glucan and BG10 (supplemented with 0.01% β-glucan). Results showed that yeast β-glucan significantly lowered (