PS5-2. Effect of Lactobacillus reuteri Supplementation on the Plasma Metabolome of Ewes.

Abstract This study investigated the effects of Lactobacillus reuteri supplementation on the performance and blood metabolome of ewes using an untargeted metabolomics approach. Eighteen crossbred Katahdin ewes of approximately (average BW = 25 ± 0.52 kg) were randomly assigned to either an unsupplemented basal diet (CON; n = 9) or a basal diet supplemented with 10 g/head/day of freeze-dried L. reuteri (LR; n = 9) for a 35-d experimental period. Weekly blood samples were collected 5 times. Plasma was prepared by centrifugation and composited for each ewe. Metabolome analysis was conducted using a chemical isotope labeling (CIL)/liquid chromatography-mass spectrometry. A total of 601 metabolite features were detected. Volcano plot analysis identified 30 differentially abundant metabolites (FDR < 0.05): with 10 metabolites upregulated including cyanamide, 2-amino-2-methyl-1,3-propanediol, dopaquinone, while 20 were downregulated, including hydroxylated lecithin, isopyridoxal, L-ornithine, tyramine, in treated ewes. Receiver operating characteristic (ROC) curve analysis identified six candidate plasma biomarkers including cyanamide, L-ornithine/D-ornithine, hydroxylated lecithin, 9-oxononanoic acid isomer 2 of sebacic acid and beta-alanine (FDR < 0.05; AUC > 0.85). Pathway enrichment indicated perturbations in amino acid metabolism, lipid metabolism, and oxidative stress pathways. These results suggest that L. reuteri modulates systemic metabolic processes in ewes, particularly nitrogen utilization and antioxidant status. Multi-omics integration with rumen microbiome and transcriptome data is warranted to elucidate mechanistic links between probiotic-induced microbial shifts and host metabolic responses.