摘要Selenium nanoparticles(SeNPs)are proposed as a safer and more effective selenium delivery system than sodium selenite(Na2SeO3).Here,we investigated the effects of replacing dietary Na2SeO3 with SeNPs synthesized by Lactobacillus casei ATCC 393 on the growth performance and gut health of early-weaned piglets.Seventy-two piglets(Duroc × Landrace × Large Yorkshire)weaned at 21 d of age were divided into the control group(basal diet containing 0.3 mg Se/kg from Na2SeO3)and SeNPs group(basal diet containing 0.3 mg Se/kg from SeNPs)during a 14-d feeding period.The results revealed that SeNPs supplementation increased the average daily gain(P=0.022)and average daily feed intake(P=0.033),reduced(P=0.056)the diarrhea incidence,and improved(P=0.013)the feed conversion ratio compared with Na2SeO3.Additionally,SeNPs increased jejunal microvilli height(P=0.006)and allevi-ated the intestinal barrier dysfunction by upregulating(P＜0.05)the expression levels of mucin 2 and tight junction proteins,increasing(P＜0.05)Se availability,and maintaining mitochondrial structure and function,thereby improving antioxidant capacity and immunity.Furthermore,metabolomics showed that SeNPs can regulate lipid metabolism and participate in the synthesis,secretion and action of parathyroid hormone,proximal tubule bicarbonate reclamation and tricarboxylic acid cycle.Moreover,SeNPs increased(P＜0.05)the abundance of Holdemanella and the levels of acetate and propionate.Correlation analysis suggested that Holdemanella was closely associated with the regulatory effects of SeNPs on early-weaned piglets through participating in lipid metabolism.Overall,replacing dietary Na2SeO3 with biogenic SeNPs could be a potential nutritional intervention strategy to prevent early-weaning syndrome in piglets.