Treatment of chickens with probiotics under conditions conducive to necrotic enteritis development

Necrotic enteritis (NE) poses a significant challenge to the global broiler industry, particularly with the increasing restrictions on using antibiotic growth promoters. Probiotics have emerged as a promising alternative for effective disease control. This study evaluated the efficacy of a probiotic cocktail consisting of Lactobacillus crispatus, Ligilactobacillus johnsonii, Limosilactobacillus reuteri, and 2 strains of Ligilactobacillus salivarius, under experimental conditions conducive to NE. Chickens were divided into two groups based on stocking density: high stocking density (30 birds/m²) and normal stocking density (15 birds/m²). Within each group, one subgroup received 10⁸ colony-forming units (CFUs) of lactobacilli on days 1, 7, 14, and 20 of age, while the other received phosphate-buffered saline. Body weight and lesion scores were recorded on days 21 and 24, respectively. Tissues from the intestine were collected for analysis of immunoregulatory genes and lymphocyte population. Cecal contents were collected for microbiome analysis. Probiotic treatment improved body weight gain compared to non-treated controls and reduced gut lesion scoring in the birds raised under high stocking density. Probiotic treatment increased the frequency of Bu-1⁺ B cells and CD3⁺CD4⁺ T cells in the cecal tonsils and enhanced the relative expression of antimicrobial peptides (zonula occludens and occludin) in the ileum. However, it decreased the expression of heat shock proteins, interleukin (IL)-18, IL-1β, and interferon (IFN)-γ. Probiotics also enhanced alpha diversity and the abundance of Christensenellaceae_R-7 group, Angelakisella, and Clostridia_vadinBB60 group compared to the high stocking density control group. These findings underscore the potential of probiotics to mitigate NE in broiler chickens, particularly under conditions of high stocking density.