Effects of β-Glucan from Paenibacillus polymyxa and L-theanine on Growth Performance and Immunomodulation in Weanling Piglets

Forty weanling piglets (5.6 +/- 0.5 kg and 26 to 30 d of age) were used in a 28-d experiment to determine the effects of beta-glucan from Paenibacillus polymyxa and L-theanine on growth performance. Piglets were randomly allotted to four groups (n = 10, 2 animals per pen) provided with the basal feed (control), beta-glucan 400 mg/kg feed, L-theanine 80 mg/kg feed or beta-glucan plus l-theanine (combination of the above-mentioned concentrations). Body weight and feed consumption were recorded during four weeks. Subsequently, the immunomodulatory effects of beta-glucan and L-theanine were investigated for lipopolysaccharide (LPS)-induced cytokine production in vitro and in vivo on day 28. Although there were no significant differences in the growth performances among the treatment groups, beta-glucan plus L-theanine had 5.6% greater ADG (p = 0.074) on day 21 to 28. beta-Glucan alone or plus L-theanine increased interleukin (IL)-10 levels and decreased interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha levels in cultured medium by LPS treatment (p<0.05). Plasma IL-10 levels were also increased in the piglets fed with beta-glucan alone or plus L-theanine after LPS challenge (25 mu g/kg, i.p.), whereas plasma IFN-gamma and TNF-alpha levels were decreased (p<0.05). The levels of IFN-gamma in piglets fed with beta-glucan plus L-theanine showed the greatest inhibition after LPS challenges. In conclusion, treatment of beta-glucan alone or plus L-theanine might lessen inflammatory responses against Gram-negative bacterial infection via the inhibition of pro-inflammatory cytokine production and enhancement of anti-inflammatory cytokine production. Further studies are needed to determine an optimal concentration of beta-glucan and L-theanine for improved growth performance.