Preliminary Investigation of Cecal Microbiota in Experimental Broilers Reared Under the Aerosol Transmission Lameness Induction Model

Bacterial chondronecrosis with osteomyelitis (BCO), and its associated lameness, is one of the most common and devastating issues the poultry industry constantly faces, both globally and domestically. Leveraging the currently accepted "leaky gut" model of pathogenesis, this study aims to evaluate the cecal community of broilers reared under the aerosol transmission BCO induction model. A trial involving 1320 Cobb 500 broilers was conducted using the same induction model for 56 d with the following treatments: (1) positive control (PC)-untreated birds on wire-flooring pens; (2) negative control (NC)-untreated birds on litter-flooring pens; (3) LOW-birds treated with probiotic <i>Enterococcus faecium</i> spray on day-of-hatch (2.0 × 10⁹ CFU/bird); and (4) HIGH-birds treated with LOW spray combined with probiotic <i>Bacillus amyloliquefaciens</i>/<i>Bacillus subtilis</i> inclusion in the diet (492.1 mg/kg). Cecal contents were collected from six birds per treatment on d14, d28, d42, and d56 of the experiment; then, DNA was extracted and sent for 16 s V3-V4 amplicon sequencing. Returned sequences were assembled and taxonomically assigned, after which diversity indices were analyzed (including alpha, beta, and abundance). No significant effect was found between all treatments and positive/negative control groups in all timepoints, but timepoints were significantly different from each other in both alpha and beta diversity indices (<i>p</i> < 0.05). Abundance analysis also showed a high Bacillota:Bacteroidota ratio (average 18.87; <i>p</i> < 0.0001) with Bacillota (Firmicutes) dominating at 95.57% on average across all treatments, followed by Bacteroidota at 5.06% and Pseudomonadota at 2.59%. These findings characterize in detail the cecal microbiome in populations of broilers reared under the novel aerosol transmission induction model, offering further insights and possibilities into studies of BCO etiology and pathology.