ABSTRACT: We studied the effects of Lactobacillus acidophilus (L. acidophilus) on the growth performance, intestinal morphology, barrier function, and immune response of broilers challenged with Escherichia coli O157 (E. Coli). A total of 360 1-day-old Cobb male broilers were tested in a 3 × 2 factorial arrangement with 3 dietary L. acidophilus levels (0, 5 × 108 CFU/kg, and 10 × 108 CFU/kg of diet) and 2 disease challenge treatments (control or E. coli challenged). Results showed that E. coli challenge decreased the ADG, ADFI, and BW of broilers from 15 to 21 d (P < 0.05), increased the jejunum intestinal wall thickness, and significantly increased the mortality rate. E. coli challenge significantly (P < 0.05) decreased the serum IgA and IgM contents and peripheral blood CD3+ T cell counts (P < 0.05), increased the serum CRP, DAO, and LPS levels at 21 d; upregulated the mRNA expression of iNOS, IL-8, IL-1β in the jejunum and iNOS in the spleen, and downregulated the occludin and ZO-1 mRNA expression in the ileum at 21 d compared with uninfected birds (P < 0.05). Dietary L. acidophilus supplementation consistently showed higher BW, ADG, ADFI, and jejunum and ileum V:C ratio at 14 d and 21 d in the presence and absence of E. coli challenge (P < 0.05). L. acidophilus supplementation reduced the mortality rate caused by E. coli challenge (P < 0.05), decreased the serum CRP, DAO, and LPS levels at 14 d and 21 d; upregulated the mRNA expression of occludin and ZO-1 in the jejunum and ileum, and downregulated the mRNA expression of iNOS, IL-8, and IL-1β in the jejunum in E. coli challenged birds at 21 d (P < 0.05). Dietary supplementation with L. acidophilus can improve the growth performance, intestinal health, and survival of broilers challenged with E. coli.
