tain the farm in a way to discourage other animals from getting into the poultry house. Additionally, they need to keep track of all visitors to the farm to prevent the introduction or spread of Salmonella or other pathogens on their farm—or their neighbor’s farm, for that matter. Indeed, the average farmer will follow biosecurity measures because he doesn’t want an infectious disease to sicken or kill his chickens, which will cause him to lose money. The problem with Salmonella, however, is that this pathogen doesn’t cause disease in chickens. Farmers don’t know their birds are infected because they look completely healthy and the birds’ growth is 50 not affected.
Salmonella in the Environment In addition to finding alternatives to antibiotics, a lot of my research has focused on ways to improve facilities or management as a way of controlling pathogens in the environment. For example, I helped develop and refine a technique known as “windrow composting” on poultry farms. The process of windrow composting allows poultry farmers to recondition the litter so they can get a little more use out of it. Typically, poultry farmers put down clean bedding once a year and then raise seven or eight flocks on the same bedding.
In agriculture in general, windrow composting is the production of compost by piling organic matter or biodegradable waste, such as manure, in long rows called windrows. On a poultry farm, you plow the litter into a pile down the center of the poultry house, allow the internal temperature to get to 130°F, and let the pile to sit for three or more days. After that time, the farmer either breaks the windrow up and spreads the litter out, or turns the pile for better pathogen reduction. By remixing the windrow a little bit, you reintroduce oxygen to the windrow, which allows the windrow to heat up again, killing bacteria, viruses, and parasites. This is not true compost because of the short period of time involved, and the process is more aptly thought of as pasteurizing the litter. This technique has been adopted nationally as a way of controlling all sorts of poultry pathogens and as a way to recondition the litter. Windrow composting between flocks eliminates another foodborne bacterium, Campylobacter, in litter and vastly reduces Salmonella and other pathogens. The process is simple but can be labor-intensive. The reason most poultry farmers are willing to go to the effort is because their chickens grow better, which means they will earn more money when the birds are sold back to the
integrator. The poultry companies are happy, because they are reducing disease and see better uniformity among the birds. Some companies have even mandated the practice, but with mixed success; if a farmer is forced to windrow and does it carelessly, the practice doesn’t work as well. I have looked at several ways to control ammonia, which can damage chickens’ lungs in poultry houses. The most common way is to acidify litter with an acidifying litter amendment, which is very effective in controlling ammonia. A pitfall with these products is that they seem to help protect Salmonella in the bedding, which can lead to colonization in the birds. A novel method we have been working on is adding microbes to the litter to control ammonia and inhibit Salmonella. These studies have shown some promise but are far from becoming practical. Some poultry companies also vaccinate birds used to breed broiler chicks and those used for egg production as a way to reduce the incidence of Salmonella. A problem is that even with vaccination there is no way to eliminate 100 percent of the Salmonella in a flock. It is like that old Listerine commercial—you can eliminate 99.999 percent of the bacteria. In an egg-laying barn, you might have a million birds, and .001 percent would mean 1,000 birds were still colonized. All it takes is one