Effect of dietary β-glucan on growth performance, fecal microbial shedding and immunological responses after lipopolysaccharide challenge in weaned pigs

Two experiments (Exp.) were conducted to evaluate the effects of β-glucan inclusion in the diet on growth performance and immune function after lipopolysaccharide (LPS) challenge. In Exp. 1, a total of 40 weaned pigs (progeny of Landrace×Yorkshire sows by Duroc) with an initial body weight (BW) of 7.89±0.84kg (21±2d) of age) were used in a 28-day (d) experiment to determine the effects of dietary β-glucan on growth performance. Pigs were allotted randomly to two treatments consisting of addition of 0 or 0.1gβ-glucan/kg diet with four replicate pens per treatment and five pigs per pen. Growth performance was not affected by β-glucan supplementation throughout the experiment. However, dietary β-glucan reduced (P<0.05) the number of fecal Escherichia coli. In Exp. 2, a total of 20 weaned barrows (6.22±0.25kg of BW and 21±2d of age) individually raised in metabolic cages were used to evaluate immunological responses following LPS challenge. Pigs were fed 0 or 0.1gβ-glucan/kg diet for 42d. At the end of the trial, half of the pigs (n=5) from each treatment were injected intraperitoneal with E. coli LPS at a concentration of 100μg/kg BW and the other half were injected with sterile saline solution. Treatments were arranged as a 2×2 factorial, with the main effect of LPS challenge (saline vs. LPS) and β-glucan supplementation (0g/kg vs. 0.1g/kg). After LPS injection, blood was taken at 0, 2, 4, 6, 8 and 12 hours (h) for the blood cell counts and blood inflammatory response. Dietary β-glucan increased (P<0.05) leukocytes counts at 4, 6 and 8h, and blood lymphocyte concentrations at 2, 4 and 6h and LPS challenge increased (P<0.05) counts of leukocytes at 2, 4, 6 and 8h and blood lymphocyte at 2 and 4h post-challenge. The rectal temperature was increased (P<0.05) at 2, 4, 6 and 8h after LPS challenge. Dietary β-glucan reduced (P<0.05) and LPS challenge increased (P<0.05) blood plasma tumor necrosis factor-α (TNF-α) concentration at 2 and 4h post-challenge. Dietary β-glucan increased (P<0.05) the concentration of the cluster of differentiation antigens 4 cells (CD4+) at 2, 4 and 6h, and of 8 (CD8+) at 4 and 6h post-challenge, respectively. The LPS challenge increased (P<0.05) CD4+ and CD8+ cell concentrations at 2, 4 and 6h post-challenge. The CD4+:CD8+ ratio was reduced (P<0.05) by LPS challenge but was increased (P<0.05) by dietary β-glucan at 2, 4, 6 and 8h post-challenge. In conclusion, dietary β-glucan decreased E. coli numbers but did not affect growth performance in weaned pigs and may offer benefits on immune function in weaned pigs challenged with LPS.