Effects of Probiotic Lactobacillus Rhamnosus on Intestinal Morphology, Blood Profiles, Immune Responses, and Ileal Gene Expression of Weaned Pigs

Abstract Probiotics are considered as a potential non-antibiotic feed additive that may improve intestinal health of pigs. However, there is limited information on potential mechanism of probiotic Lactobacillus rhamnosus. The study was carried out to evaluate effects of probiotic Lactobacillus rhamnosus on intestinal morphology, blood profiles, immune responses, and ileal gene expression of weaned pigs. In a randomized complete block design [block: initial body weight (BW)], a total of 100 weaned pigs (7.99 ± 0.85 kg of average initial BW; 28 days of age) were assigned to two dietary treatments (5 pigs/pen; 10 replicates/treatment). Dietary treatments were fed for 4 weeks: 1) a commercial basal nursery diet (CON), and 2) CON + 0.02% probiotic Lactobacillus rhamnosus IDCC 3201 (PRO). Probiotic Lactobacillus rhamnosus was obtained from a commercial company (ILDONG Bioscience Co., Ltd., Pyeongtaek, Republic of Korea). Blood was collected from randomly selected one pig per pen on day 1, 7, 14, and 28 for blood profiles and immune responses. On the final day of study, pigs were euthanized to collect each part of small intestine for measuring intestinal morphology and ileal gene expression. Measurements were 1) villus height, width, and area, crypt depth, villus height to crypt depth ratio (VH:CD), and number of goblet cells by the hematoxylin and eosin staining method, 2) number of white blood cells (WBC), red blood cells (RBC), and hematocrit (HCT) by an automated hematology analyzer calibrated for porcine blood, 3) immunoglobulin G (IgG), IgA, tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1), interleukin-10 (IL-10), and C-reactive protein in serum by the ELISA kits, and 4) ileal gene expression of tight junction-related proteins and inflammatory cytokines by qRT-PCR. Data were analyzed using PROC GLM of SAS. Experimental unit was the pen. Statistical model for intestinal morphology, blood profiles, and immune responses included dietary treatment as a main effect and initial BW as a covariate. The t-test was used for ileal gene expression. The PRO increased number of goblet cells in duodenum (P < 0.05) and VH:CD in ileum (P < 0.10) compared with CON. Pigs fed PRO had decreased HCT on day 7 (P < 0.10), WBC on day 28 (P < 0.05), and serum IgA concentrations on day 28 (P < 0.05) than those fed CON, but RBC on day 7 and 14 were greater (P < 0.05). The PRO upregulated (P < 0.05) claudin-3, occludin, tight junction protein-1 genes in ileum compared with CON, but TNF-α, interferon-α, IL-1α, IL-1β, IL-6, and IL-8 genes were downregulated (P < 0.05). In conclusion, addition of probiotic Lactobacillus rhamnosus in the nursery diet improved gut health via enhancing intestinal morphology and upregulating ileal tight junction-related protein genes, and modified blood parameters and ileal inflammatory cytokine genes.