Effects of Dietary Administration of Egg Yolk Antibody Powder on Growth Performance, Intestinal Escherichia coli Colonization, and Immunocompetence of Challenged Broiler Chicks
The present study aimed to investigate the effects of dietary supplementation of different levels of specific (sIgY) and non-specific (nsIgY) egg yolk antibody powder on growth performance, immune functions, and intestinal morphology of E. coli O78:K80-challenged broiler chicks. Lyophilized antibody isolated by the water-dilution method was obtained from the eggs of laying hens hyperimmunized with E. coli O78:K80. Seven days-aged broiler chicks were challenged orally with 0.5 mL of E. coli O78:K80 suspension. The treatment was continued for additional 7 days from d 14 to 21 with 1.0 mL of a late log phase culture (109 cfu/mL), until the level of E. coli in feces reached to 105 cfu/g. A total of 392 broiler chicks were randomly assigned to 7 dietary treatments with 4 replicates of 14 chicks (7 males and 7 females) each. The six challenged groups received a basal diet supplemented with 0 (as positive control), 0.1, 0.2, or 0.4% (wt/wt) sIgY from eggs of immunized hens, or levels of 0.2 or 0.4% (wt/wt) nsIgY from eggs laid by the nonimmunized hens. The negative control group fed the same unsupplemented diet. Oral infection caused increase in ileal E. coli enumeration, and induces systemic and mucosal inflammatory reactions. After three weeks of feeding, the levels of 0.2 and 0.4% sIgY and 0.4% nsIgY had the most suppressive effects (P < 0.01) on the ileal E. coli enumeration and intestinal secretory IgA concentration. However, serum IgA concentration was slightly decreased only at the presence of 0.4% sIgY and nsIgY. Dietary supplementation with at least 0.2% sIgY decreased (P < 0.05) the heterophils to lymphocytes ratio. Inclusion of both sIgY and nsIgY increased the villus height to crypt depth ratio, and decreased the jejunal goblet cells and lamina propria lymphatic follicles numbers, with the most pronounced effects assigned to sIgY-supplemented groups. The best feed conversion ratio obtained when the dietary inclusion of at least 0.2% sIgY continued for three weeks. In conclusion, the present results indicate that dietary administration of at least 0.2% sIgY for three weeks could improve the intestinal health indices and growth performance of broiler chicks orally challenged by E. coli O78:K80.