Abstract
Heat stress during summer significantly impairs seminal quality in swine production. As a key genetic resource for enhancing indigenous Chinese fatty pig breeds, Ningxiang boars require effective nutritional strategies to maintain reproductive performance under thermal challenge. This study aimed to investigate the effects of a combined antioxidant dietary supplement on seminal quality, antioxidant status, and gut microbiota in heat-stressed Ningxiang boars. Ten Ningxiang boars were randomly assigned to two groups (n = 5 per group). The control group received a basal diet, while the experimental group was fed the same basal diet supplemented with 400 mg/kg vitamin E, 5 g/kg yeast-derived zinc, 250 mg/kg yeast-derived selenium, and 800 mg/kg N-carbamylglutamate (NCG). Results demonstrated that sperm and seminal plasma superoxide dismutase (SOD) activity was significantly elevated in the supplemented group compared to the control (p < 0.05), whereas malondialdehyde (MDA) levels and total antioxidant capacity (T-AOC) did not differ significantly (p > 0.05). 16S rRNA gene sequencing revealed that dietary supplementation combined antioxidant markedly altered gut microbiota composition: the abundance of short-chain fatty acid-producing bacteria, particularly members of the Muribaculaceae family, increased significantly (p < 0.05), while opportunistic pathogens within the Acholeplasmataceae family were reduced (p < 0.05). These findings suggest that dietary supplementation with this antioxidant combination improves seminal quality in Ningxiang boars, potentially by enhancing endogenous antioxidant defenses and modulating gut microbial balance.