Selenium-enriched probiotics improve growth performance in PCV2-infected weaned piglets by regulating antioxidant...

Infection with porcine circovirus type 2 (PCV2) can increase oxidative stress, impair immune function and reduce growth performance in weaned piglets. Selenium-enriched probiotics (SeP), as a novel form of organic selenium (Se), have attracted increasing attention due to their combined nutritional and immunomodulatory properties. However, the effects of SeP on weaned piglets under PCV2 infection conditions remain unclear. This study focused on weaned piglets from a PCV2-positive pig farm in Jiangsu Province. A total of 60 piglets were randomly divided into 5 groups, with 3 replicates per group and 4 piglets per replicate. The control group was fed a basal diet, while the experimental groups received basal diets supplemented with sodium selenite (Na₂SeO₃) or SeP at levels of 0.3 mg/kg and 0.6 mg/kg, respectively. This study systematically evaluated thegrowth performance, antioxidant capacity, immune function, and PCV2 infection levels in weaned piglets. Compared with the control group, Se supplementation significantly increased daily weight gain and feed-to-gain ratio (F/G) while decreasing the feed-to-gain ratio in weaned piglets (P < 0.05). Se supplementation significantly increased serum glutathione peroxidase (GPX) and superoxide dismutase activity while decreasing malondialdehyde content. It also significantly upregulated mRNA expression levels of selenoprotein-related genes including GPX1, GPX4, and Thioredoxin Reductase 1 (TR1) in blood (P < 0.05). In terms of immune regulation, supplementation with Na₂SeO₃ or SeP significantly increased serum levels of interleukin-2 and tumor necrosis factor-α, while enhancing the proliferative capacity of peripheral blood lymphocytes (P < 0.05). Additionally, Se supplementation significantly reduced the copy number of PCV2 DNA in the blood of PCV2-infected weaned piglets (P < 0.05). Comprehensive analysis revealed that SeP demonstrated superior overall efficacy compared to Na₂SeO₃ in enhancing growth performance, boosting antioxidant and immune functions, and suppressing PCV2 replication. This study provides a theoretical basis for employing SeP as a precise nutritional strategy in pig populations affected by PCV2.