Algae-derived β-glucan enhanced gut health and immune responses of weaned pigs experimentally infected with a pathogenic E. coli

Most of the commercially available β-glucans are derived from yeast, while there are limited research on algae-derived β-glucan in pigs. Therefore, the objective of this experiment was to investigate the influence of dietary supplementation of algae-derived β-glucan on diarrhea, gut permeability, and immune responses of weaned pigs experimentally infected with a pathogenic Escherichia coli (E. coli). Thirty-six weaned pigs (7.69 ± 0.77 kg BW) were individually housed in disease containment rooms and randomly allotted to one of three dietary treatments (n = 12): control diet and 2 additional diets containing either 54 or 108 mg/kg of β-glucan. The experiment lasted 17 d [5 d before and 12 d post inoculation (PI)]. The inoculum used in this experiment was F18 E. coli, containing heat-labile toxin, heat-stable toxin b, and shiga-lie toxin 2. The inoculation doses were 10¹⁰ cfu/3 mL oral dose daily for 3 days. Diarrhea score (1, normal, to 5, watery diarrhea) was recorded for each pig daily to calculate frequency of diarrhea. Blood samples were collected on d 0 before E. coli challenge, and on d 2, 5, 8, and 12 PI to measure total and differential blood cell count in whole blood and several inflammatory markers in serum. Fresh jejunal tissues were collected from 4 pigs in the control group and high dose β-glucan group to analyze gut permeability on d 5 and d 12 PI with Ussing Chamber. Jejunal and ileal mucosa were also collected to measure the mRNA expression of several genes related to gut barrier function and immune responses. Results of this experiment revealed that inclusion of high dose β-glucan reduced (P < 0.05) frequency of diarrhea (29.01% vs. 17.28%) for the entire experimental period. This was likely due to the reduced (P < 0.05) gut permeability and increased (P < 0.05) mRNA expression of gut barrier function genes (Claudin, Occludin, and MUC2) in jejunal mucosa of E. coli challenged pigs as β-glucan supplemented. Supplementation of β-glucan also reduced (P < 0.05) white blood cells, neutrophils, serum tumor necrosis factor (TNF)-α cortisol, and haptoglobin, and down-regulated (P < 0.05) the mRNA expression of several immune genes (IL1B, IL6, and TNFA) in ileal mucosa of E. coli challenged pigs, compared with the control diet. In conclusion, in feed supplementation of algae-derived β-glucan alleviated diarrhea of F18 E. coli infected pigs by enhancing gut integrity. Feeding β-glucan also boosted host immune response against E. coli infection.