Intestinal colonization with affects broiler gut microbiota composition but is not inhibited by daily intake of .

Introduction: Lactobacilli may prevent broilers from colonization with spp. and other gram-negative zoonotic bacteria through lactic acid production and modulation of the intestinal microbiota. This study evaluated the effects of daily intake of 256 (LP256) on loads in ceca and feces of challenged broilers, together with the changes in the gut microbiota.

Methods: Two experiments were conducted using the broilers Ross 308 (R-308; Experiment 1) for 42 days and Rowan Ranger broilers (RR; Experiment 2) for 63 days. The strain was administered either via silage inoculated with or direct supplementation in the drinking water. Concurrently, haylage as a forage similar to silage but without any inoculum was tested. loads in fecal matter and cecal content were determined by plate counts and qPCR, respectively. The cecal microbiota, in response to treatments and the challenge, were assessed by 16S rRNA sequencing.

Results And Discussion: Culturing results displayed a significant reduction in colonization (2.01 log) in the silage treatment in comparison to the control at 1 dpi (day post-infection) in Experiment 1. However, no treatment effect on was observed at the end of the experiment. In Experiment 2, no treatment effects on colonization were found to be statistically significant. Colonization load comparison at the peak of infection (3 dpi) to that at the end of the trial (32 dpi) revealed a significant reduction in in all groups, regardless of treatment. Colonization dynamics of in the cecal samples analyzed by qPCR showed no difference between any of the treatments in Experiment 1 or 2. In both experiments, no treatment effects on the cecal microbiota were observed. However, proportional changes in the bacterial composition were observed after the challenge, suggesting that colonization affected the gut microbiota. Overall, the daily intake of was not effective in reducing colonization in either broiler type at the end of the rearing period and did not cause any significant changes in the birds' cecal microbiota composition.