The Effect of Arginine Supplementation on Intestinal Antioxidant Capacity, Whole Blood Cell Count and Antiviral Immune Function of Piglets Infected with Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea virus (PEDV) imposes substantial economic losses on the global swine industry owing to its high pathogenicity and transmissibility. Although arginine (Arg) is known to support the integrity of intestinal barrier, it is not clear whether Arg can alleviate intestinal injury induced by PEDV. A total of 32 healthy 7-day-old piglets were randomly assigned to four groups (Control, Arg, PEDV, PEDV + Arg; eight replicates per group). From day 5, piglets in the Arg and PEDV + Arg groups were orally administered Arg at 400 mg/kg body weight until day 11; then, PEDV (1 × 105.5 TCID50) was given orally for two PEDV-infected groups. On day 14, all piglets were slaughtered to obtain blood and intestine samples for further analysis. The results showed that PEDV infection significantly reduced T-SOD and CAT activities in plasma and intestine while elevating MPO levels. Arg supplementation restored T-SOD (plasma, duodenum, ileum), CAT (plasma, ileum), and GSH-Px (jejunum, ileum) activities and reduced MDA (jejunum) content in PEDV-infected piglets. Hematological analysis showed Arg alleviated PEDV-induced increases in MCV and RDW-SD, and significantly elevated MCHC. The real-time quantitative PCR analysis demonstrated that Arg further enhanced PEDV structural genes (M, N, S) expression in the duodenum, ileum, and colon. Concurrently, Arg significantly up-regulated interferon-stimulated genes (MX1, OASL, ISG15, IFITM3) in the ileum, IRF7 in the duodenum and colon, and IFN-β in the ileum. Arg also down-regulated the pro-inflammatory cytokines IL-6 and CXCL2 and the antimicrobial peptide REG3G in the colon, while up-regulating the tissue repair gene MMP13 in the ileum. In conclusion, oral Arg exhibits a unique dual role: it promotes PEDV replication to a certain extent while significantly enhancing antioxidant capacity, strengthening intestinal antiviral immunity, and attenuating intestinal inflammation. These findings highlight Arg’s role in promoting disease tolerance and offer a novel perspective for nutritional intervention strategies against PEDV infection.