Evaluation of Dietary Additives on the Antimicrobial Activity against Campylobacter jejuni Colonization in Broilers

Abstract

In the United States, campylobacteriosis is one of the most reported bacterial foodborne illnesses. Chickens are a natural and common reservoir for Campylobacter jejuni, and poultry chicken meat is the most frequently cited source of human infection. Reducing levels of Campylobacter jejuni in chickens could reduce risk of human exposure and have a significant impact on food safety and public health. The objectives of the present dissertation were to evaluate feed and water additives and their ability to reduce Campylobacter jejuni intestinal colonization in broilers, as well as their impact on gut health and broiler performance. The first 2 trials evaluated the use of yeast cell walls (YCW) as dietary additives in broilers that were and were not inoculated with Campylobacter jejuni. The dietary treatments evaluated were negative control, positive control (bacitracin, 50 g/ton), YCW constant dose (400 g/ton), and YCW step-down dose (800, 400, and 200 g/ton in the starter, grower, and finisher periods, respectively). Trial 1 was inoculated with a 107 –colony-forming-units (CFU)/mL dose at day 21 and trial 2 was inoculated with a 103 CFU/ml dose at day 16. In trial 1, an instance of cross-contamination occurred between broilers inoculated with Campylobacter jejuni and those inoculated with phosphate buffered saline (PBS), leading to Campylobacter colonization in PBS-inoculated birds. In both trials, Campylobacter jejuni cecal colonization levels were comparable among broilers consuming different diets. The average Campylobacter colonization level in trial 1 at day 42 was 8.4 log10 CFU/g of cecal content for both Campylobacter- and PBS-inoculated birds. In trial 2, the average Campylobacter colonization levels were 6, 8.3, and 8.1 log10 CFU/g of cecal contents at days 24, 34, and 42, respectively (P>0.05), and all PBS-inoculated birds were negative for Campylobacter jejuni prevalence. Under the conditions of both trials, the dietary addition of YCW did not have an impact on the innate immune response, growth performance, carcass yield, or carcass contamination after processing in broilers (P>0.05). Additionally, in trial 1, no differences were observed in gut histomorphometry among birds consuming different diets or types of inoculation (P>0.05). Regardless of the inoculation dose, it was observed that Campylobacter jejuni colonization levels in the ceca of broilers reaches high numbers (>8 log10 CFU/g), which suggests that Campylobacter colonization does not follow a linear dose response. For trial 3, acidification of water using organic acids was evaluated to determine the antimicrobial activity against Campylobacter jejuni. Broilers were randomly assigned to 1 of 4 water treatments groups: negative control (water), intermittent organic acid A (2 mL/L; days 1 to 5 then 1 day per week), continuous organic acid A (2 mL/L), and continuous organic acid B (2.6 mL/L) and to 1 of 2 inoculations: PBS or Campylobacter jejuni at 104 CFU/mL administered via oral gavage on day 21. The inclusion of organic acids in water did not affect the levels of Campylobacter cecal colonization at any time point analyzed (P>0.05) and the average Campylobacter cecal colonization levels at day 42 were 8.8 log10 CFU/g. An effect of the inclusion of organic acid A was observed in broiler body weight at day 41, in which broilers consuming water acidified with organic acid A had heavier body weights (P=0.0029) than the age-matched negative controls and broilers consuming organic acid B. No effects of the organic acids were observed in gut histomorphometry or cecal microbiome (P>0.05). However, the type of inoculation impacted the intestinal structure at the jejunum and ileum, where birds inoculated with Campylobacter jejuni had increased crypt depth in the jejunum (P=0.0018) and reduced villus height and villus height to crypt depth ratio in the ileum (P=0.0134 and P=0.0003, respectively) than birds inoculated with PBS. Similarly, inoculation with Campylobacter jejuni significantly impacted the alpha- and beta-diversity of the cecal microbial populations (P<0.01). Based on the overall Campylobacter jejuni recovery from cecal contents of broilers provided with either dietary YCW or organic acids in water, further studies evaluating the efficacy of different additives, alone or in combination, are warranted to successfully reduce Campylobacter colonization in broilers during grow-out.