Effect of Dietary Prebiotic Supplementation on the Immune Response and Intestinal Health Following Eimeria Infection of Broiler Chicken

Background: Antibiotics are preferred drugs for controlling coccidiosis. However, prolonged use of ionophores will result in Eimeria resistance to these drugs. Objectives: The present work was conducted to evaluate the possible substitution of prebiotic (nutri yeast [NY]) for antibiotics in mild-challenged broilers with Eimeria. Methods: A total of 420 1-d-old male Ross 308 chicks were used in a completely randomized design with 7 treatments and 5 replicates. Experimental treatments included: 1) Negative control (NC) (without prebiotic and challenge); 2) Positive control (PC) (without prebiotic and challenged with sporulated oocysts of Eimeria [SO]); 3) 0.2% NY in starter, 0.1% in grower, 0.05 % in finisher, challenged with SO; 4) 0.2 % NY in starter, 0.1 % in grower, 0.05 % NY in finisher, without challenge; 5) 0.2% NY in the whole rearing period of chicks challenged with SO; 6) 0.2% NY in the whole rearing period of chicks without challenge; and 7) Salinomycin (0.05 % of diet). At 7 d of age, treatments 2, 3 and 5 were challenged with a 20-fold dose of Eimeria vaccine via oral gavage. Antibody levels against sheep red blood cell (SRBC) were measured at 31 and 41 days of age. On days 28 and 42, two birds per replicate were slaughtered to collect ileal digesta for microbial analysis. Samples were collected for blood metabolite parameters, carcass traits and visceral organ weight, intestinal morphology, and interleukin 6 (IL-6) gene expression on day 42. Results: The results showed that NY supplementation increased the concentration of serum total protein (3.10 vs 2.57 g/dL) and decreased serum triglycerides (50.6 vs 57.3 mg/dL) and cholesterol (108.6 vs 133.9 mg/dL) levels compared to NC group (P<0.05). Serum antibody titers against Newcastle were higher in prebiotic treatments compared to control groups, and for the secondary immune response against SRBC broilers fed NY diet had the highest levels of total Ig (8.4 vs 6.4) and IgG (5.6 vs 4.2) compared to the control group (P<0.05). The inclusion of NY improved intestinal pH and the relative weights of immune organs, breast muscle, and small intestine compared to the NC treatment (P<0.05). Villus height (806.6 vs 578.7 μm) and numbers of lactobacillus (8.77 vs 8.29 CFU/g) increased, while crypt depth (112.8 vs 144.9 μm) and numbers of coliforms (6.19 vs 6.61 CFU/g) decreased in broilers fed a diet containing NY compared to the NC group (P<0.05). Dietary supplementation of NY decreased IL-6 gene expression in challenged and unchallenged birds compared to the control group (P<0.05). Conclusion: The results of the current study confirmed our hypothesis that the use of prebiotic (NY) has protective activities against coccidiosis in broiler chicks.