Effects of dietary Enterococcus faecium NCIMB 11181 supplementation on growth performance and cellular and humoral immune responses in broiler chickens

This study evaluated the effects of dietary Enterococcus faecium NCIMB 11181 on growth performance and immune response in broiler chickens. A total of 360 1-day-old Arbor Acres male birds were randomly assigned to 4 treatments that administered different dosages of E. faecium (0, 5 × 107, 1 × 108, and 2 × 108 CFU E. faecium/kg diet). The results revealed that average daily gain (ADG) changed quadratically, while feed conversion rate (FCR) increased linearly from day 22 to 35 and day 1 to 35 (P < 0.05). Supplementation of E. faecium at 5 × 107CFU/kg diet resulted in increased ADG (P < 0.05) compared with the other groups. Birds fed with 2 × 108 CFU/kg E. faecium exhibited increased peripheral blood lymphocyte proliferation in response to concanavalin A (Con A) (P < 0.05) at day 35 and enhanced skin responses following phytohemagglutinin (PHA) injection (P < 0.05) at 12 h. Serum lysozyme activity at day 21 increased linearly with dietary E. faecium concentration (P < 0.05), the highest activity was observed in the 1 × 108 and the 2 × 108 CFU E. faecium groups (P < 0.01). Serum levels of proinflammatory cytokines IL-1β, IL-2, IL-6, IFN-γ, and anti-inflammatory IL-4, IL-10 changed linearly or quadratically both at the initial and final phases (P < 0.05). In addition, BSA antibody titers were significantly increased following both primary and secondary inoculation when birds were fed with 1 × 108 or 2 × 108 CFU/kg E. faecium (P < 0.05). In comparison with other groups, birds received 5 × 107 CFU E. faecium exhibited the highest levels of serum IgG (P < 0.05) at day 35. Together, our results revealed that broiler diet supplemented with 5 × 107 CFU/kg E. faecium NCIMB 11181 was appropriate in relation to growth performance under normal conditions. Upon administration with higher dosages of E. faecium NCIMB 11181, obvious immune-stimulatory effects were observed following both cell-mediated and humoral immunity.