KONGENS LYNGBY, Denmark – Researchers are investigating feed additives to reduce Campylobacter in free-range broilers.

Campylobacter is a type of bacteria that commonly colonizes the intestinal tracts of chickens. The bacteria are highly prevalent in poultry worldwide, and it can be transmitted to humans through contaminated meat that hasn’t been thoroughly cooked. The Centers for Disease Control and Prevention estimates that about 1.5 million people in the U.S. get ill from Campylobacter each year. Worldwide, the bacterial infection is one of four key global causes of diarrheal disease, according to the World Health Organization.

In 2022, the Danish Veterinary and Food Administration released its latest action plan with the goal of reducing Campylobacter in chicken. The action plan brings together the government, universities, and industry partners to create initiatives for a better public health, said Brian Lassen, senior researcher at the National Food Institute, part of the Technical University of Denmark. Through collaboration, research groups can identify sources of the bacteria and identify possible interventions.

Lassen and his colleagues recently published research demonstrating the effectiveness of different feed additives to prevent Campylobacter in free-range chickens. The motivation for focusing on free-range and organic chickens is because those flocks have different biosecurity options than those on conventional farms, Nao Takeuchi-Storm, researcher at the National Food Institute, said. The animals are exposed to the outdoors, have a longer life than conventionally raised chickens, and organic farmers are restricted in what they can give to their animals as a biosecurity measure against Campylobacter.

An extensive literature review identified several feed and water additives that the team was interested in exploring in a production environment. The study focused on the effectiveness of 2 percent Biochar Charcoal Feed Granules for Poultry, 0.125 percent Original XPC (a postbiotic containing fermented yeast cells), 15 percent oat hulls, and organic acids added (0.2 percent Selko®pH E (v/v)) to water. One hundred and forty newly hatched Ranger Gold broilers were randomly placed into five cages within a flock of 6,000 broilers with access to outdoor areas after day 36 of the experiment. Each of the five groups of broilers received a different feed or water additive, with the fifth group receiving standard feed pellets and water.

Three successive flocks were studied in this manner, with half of the broilers slaughtered on day 36 of the experiment and the other half on day 59 to study the concentration of Campylobacter at different time points. Samples were also collected from feed, water, and dust in the environment to determine the exact moment the flock became colonized by Campylobacter, Cristina Calvo-Fernández, a doctoral student, explained.

“Another reason for choosing to study (the animals) at day 36 was that we hypothesized that maybe some of these interventions potentially could be useful in conventional farming, with 36 days being the approximate age of conventional broilers (at slaughter), and the day before the farmer would give the chicken access to the outdoors,” Lassen added.

The results of the study demonstrated that it is possible to reduce Campylobacter in the flocks studied at day 59 during normal production conditions by adding the biochar feed supplement throughout the rotation. Additionally, the researchers observed that the organic acids added to drinking water reduced the bacteria at day 36, but the effect diminished in the group slaughtered at day 59.

“There’s quite a bit of variation in the experiment’s flocks,” Takeuchi-Storm said. “The significant result (of biochar’s effectiveness) was only seen in two out of the three rotations. It’s not always showing results – each flock is very different. We don’t know if variations are due to the season or how the flock was managed, but each flock is very different in how they get colonized by the bacteria.”

For example, Lassen noted that there has been an ongoing debate about free-range broilers picking up Campylobacter from the outdoors. However, the team observed Campylobacter present in indoor dust samples and that the birds were infected before they went outside. Challenges with proper cleaning and disinfection to eliminate Campylobacter from the house environment is a well-known problem. Additionally, the bacteria strains differed between indoor and outdoor environments.

Next, the team is interested in investigating the microbiome data collected from the broilers in the study to begin to understand at a molecular level how Campylobacter is reduced by different additives. The group will also continue to investigate biochar as a potential feed additive and explore which form of biochar is the most effective and how the administration (pelleted or not) affects the result. Overall, the goal of the research is to reduce the prevalence of foodborne pathogens and improve public health, Calvo-Fernández said.