Probiotic Combination of Lactiplantibacillus plantarum M1 and Limosilactobacillus reuteri K4 Alleviates Early Weaning-Induced Intestinal Injury in Lambs via Modulation of Oxidative and Inflammatory Pathways

Early weaning in intensive lamb production improves reproductive efficiency but predisposes lambs to diarrhea, oxidative stress, and intestinal barrier dysfunction, highlighting the need for non-antibiotic strategies to protect gut health. This study evaluated whether a sheep-derived mixed probiotic could alleviate early weaning–induced intestinal injury and clarified its potential molecular mechanisms. Early weaning reduced body weight, average daily gain and feed efficiency, increased diarrhea, decreased plasma and colonic catalase (CAT), glutathione peroxidase (GSH-PX), and superoxide dismutase (SOD) activities, increased malondialdehyde (MDA), elevated interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), reduced interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), increased plasma and mucosal immunoglobulin A, M, and G (IgA, IgM, IgG), and increased colonic lipopolysaccharide (LPS) with reduced diamine oxidase (DAO). Intestinally, EW induced villus atrophy, deeper crypts, lower villus height-to-crypt depth ratios, goblet cell loss, higher histopathological scores, and decreased colonic mucin 2, zonula occludens-1, claudin-1, and occludin. Probiotic supplementation partially reversed these alterations, restoring antioxidant enzyme activities, improving villus architecture and barrier protein expression, and rebalancing cytokine and immunoglobulin profiles. Transcriptomic and network analyses showed that early weaning activated Cytokine–cytokine receptor, NF-κB, TNF and Th17 pathways, whereas probiotics suppressed a weaning-responsive inflammatory gene module, downregulated key hub genes, and enhanced peroxisome proliferator-activated receptor (PPAR) signaling. These results show that supplementing early-weaned lambs with a mixed probiotic generated from sheep is an efficient nutritional strategy to reduce intestinal oxidative and inflammatory damage associated with weaning and to enhance their health and performance.