| Beta-glucans (beta-glucans) are polysaccharides naturally present in cereal grains, fungi, seaweed, and algae. It has been known that beta-glucans possess anti-inflammatory, anti-tumor, and perhaps immunomodulatory effects. The current study evaluated the effects of algae-derived beta-glucan on performance, diarrhea, gut barrier function, and immune responses of weaned pigs experimentally infected with F18 Escherichi coli ( E. coli). Thirty-six weaning pigs (7.69 +/- 0.77 kg BW, 21 d old) were individually housed in disease containment rooms and randomly allotted to one of the four treatments with 12 replicate pigs per treatment. The three diets were a nursery basal diet (Control), and 2 additional diets containing either 54 or 108 mg/kg of algae-derived beta-glucan in the basal diet. The experiment lasted 17 days with 5 days before and 12 days after the first inoculation (d 0). The inoculum used in this experiment was F18 E. coli, containing LT, STb, and SLT2 toxins. The inoculation doses were 1010 cfu/3 mL oral dose daily for 3 days. The growth performance was measured on d 0 to 5, 5 to 12, and 0 to 12 post-inoculation (PI ). Diarrhea score (1, normal, to 5, watery diarrhea) was recorded daily for each pig. Frequency of diarrhea was the percentage of pig days with diarrhea score of 3 or higher. Rectal temperature was measured for each pig daily after first inoculation. Blood samples were collected right before E. coli challenge, and on d 2, 5, 8, and 12 post-inoculation. Total and differential blood cell count were analyzed by CBC test. The concentration of CD4+ T cells, CD8+ T cells, and B cells were analyzed by flow cytometry. The concentrations of cytokines (TNF-alpha, IL-6, and IL-10), cortisol, and haptoglobin in serum samples were analyzed by enzyme-linked immunosorbent assay kits. On d 5 and d 12 PI, middle of jejunum were collected from 4 pigs in the control group and high dose beta-glucan group for transcellular and paracellular permeability analysis using Ussing chamber.;Intestinal mucosa samples were collected from the jejunum and ileum on d 5 and 12 PI and were snap-frozen in liquid nitrogen for gene expression analysis. The mRNA expression of zona occludens-1 (ZO-1), Claudin, Occludin, MUC2, and Dectin in jejunal mucosa and COX2, IL1B, IL6, TNFA, MUC2, and Dectin in ileal mucosa were analyzed by qRT-PCR. Data normalization was accomplished using ACTB and GAPDH as housekeeping genes. All data were analyzed by ANOVA using the PROC MIXED of SAS with pig as the experimental unit. The Chi-square test was used for the frequency of diarrhea analysis. No differences were observed in body weight, average daily gain, average daily feed intake, and feed efficiency of pigs throughout the experiment among dietary treatments. Inclusion of 108 mg/kg of beta-glucan reduced (P < 0.05) frequency of diarrhea for the entire experimental period. Supplementation with 54 mg/kg of beta-glucan reduced (P < 0.05) the number of white blood cells and neutrophils, and inclusion of either 54 or 108 mg/kg of beta-glucan reduced (P < 0.05) basophil number compared with the control diet on d 8 PI. Supplementation with 54 mg/kg of beta-glucan increased (P < 0.05) the percentage of CD4+ T cells in lymphocytes on d 2 and 5 PI compared with the control diet. Feeding 108 mg/kg of beta-glucan increased (P < 0.05) the percentage of CD8+ T cells in lymphocytes on d 5 PI but reduced (P < 0.05) the percentage of CD8 + T cells in lymphocytes on d 12 PI compared with the control diet. Supplementation with either 54 or 108 mg/kg of beta-glucan reduced (P < 0.05) serum haptoglobin on d 2 and 5 PI, reduced (P < 0.05) serum cortisol on d 5, 8, and d 12 PI compared with the control diet. Pigs fed the diet supplemented with 108 mg/kg of beta-glucan had lower (P < 0.05) serum TNF-beta concentration on d 5 PI. Inclusion of 108 mg/kg of beta-glucan reduced ( P < 0.05) jejunal transcellular permeability of E. coli infected-pigs on d 12 PI compared with pigs fed the control diet. On d 5 and 12 PI, supplementation with 108 mg/kg of beta-glucan up-regulated (P < 0.05) the mRNA expression of Dectin in jejunal mucosa, and down-regulated (P < 0.05) gene expression of IL6 in ileal mucosa of E. coli challenged pigs compared with the control diet. (Abstract shortened by ProQuest.). |
