When many of us hear about bacteria, we associate it with illness. But certain bacteria can be helpful in preventing disease, not causing it. For example, consuming probiotics, or beneficial bacteria, to improve gut health has risen in popularity in recent years, both for human and animal wellness.

A joint research collaboration between the University of Georgia’s Department of Poultry Science and the U.S. National Poultry Research Center (USNPRC), housed within the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS), has been investigating the role that bacteria play in poultry health and food safety. New research from this group has found that the type of litter broiler chickens are raised on plays an important role in their pre-harvest health.

Specifically, reusing litter instead of supplying fresh litter every time can help bolster the birds’ immune systems. The same study also showed that reusing litter may help prevent the transfer of antibiotic resistance between bacterial species.

“Similar to the way human breastmilk contains good bacteria that helps boost a human baby’s immune system, litter is the first bacteria that chicks encounter and it also boosts their immune system. Chickens raised on fresh litter only get the microbiome of the litter itself, which is mostly just wood shavings,” said the study's lead author Adelumola Oladeinde, a research microbiologist with USNPRC and adjunct faculty in UGA's College of Agricultural and Environmental Sciences.

Oladeinde and his collaborators started by infecting the chickens used in the study with a strain of Salmonella that was not antibiotic-resistant. Some of those chickens were then raised on fresh litter while others were raised on reused litter — a mixture of wood shavings, feces, uric acid, feathers and chicken feed.

At the end of the study, chickens raised on reused litter had a lower Salmonella positivity rate (66%) compared to chickens raised on fresh litter (79%). Additionally, the researchers found that some of these Salmonella-infected chickens on fresh litter were infected with a multi-drug resistant strain of Salmonella, while they found no multi-drug resistant Salmonella in chickens on reused litter.

This was particularly intriguing because the Salmonella strain the researchers used for the initial infection was not a multi-drug resistant strain. After investigating further, they discovered that this resistance was transferred from E. coli bacteria living within the chickens’ digestive systems.

The research shows that reusing litter can play a vital role in poultry health, as well as controlling the spread of antibiotic-resistant foodborne bacteria. Oladeinde explained that these findings have global implications, considering the rise of antibiotic resistance around the world. Reusing litter is also a cost-saving measure for the poultry industry to not have to buy fresh litter for every flock.

“There is a notion that reusing litter to raise multiple flocks of chickens can only be bad, which has hampered the widespread adoption of litter reuse. These contradictory attitudes towards litter recycling show that we need more research focused on poultry litter,” Oladeinde said.

However, recycling litter can lead to the accumulation of high ammonia levels in broiler houses, which can impact workers’ health. Industry practice when reusing litter in the U.S. is for poultry house owners to change out the litter after at least one year, or six flocks — but some poultry houses have been reusing litter for more than a decade with no issues.

While reusing litter over multiple broiler flocks is common in the U.S. and Brazil, two major poultry-producing countries, Canada recommends fresh litter for every flock, and some European countries have banned reusing litter altogether. Not only is more research needed on this subject, but more collaboration and information sharing between industry and scientists is important as well.

This is where the UGA poultry science department’s research and outreach efforts are key.

“Working with UGA and their poultry research center helps make the industry connection. Farmers are reluctant to share with researchers without a feeling of trust, which UGA has worked to establish,” Oladeinde said.

The collaboration between UGA’s Department of Poultry Science and USPRNC began in 2018 and is one of the most intensive concentrations of poultry researchers in the world. According to Oladeinde, there is immense potential for impactful research and success to come from this collaboration in the future, as both entities have an international standing in poultry research.

“This research is a great example of successful collaboration and partnerships between UGA faculty and USDA-ARS scientists and others across the U.S. These collaborations are key to elevating the depth and types of research questions we can collectively address,” says Todd Applegate, head of the Department of Poultry Science and R. Harold and Patsy Harrison Chair in Poultry Science at CAES.