"Because chickens spread salmonella horizontally, when there are fewer birds, it spreads less," he said.
The organic chickens Alali studied came from three USDA-certified organic farms, not to be confused with free-range farms.
The chickens on organic farms are kept in houses just like on conventional farms, except the houses are brighter and more open to give the chickens more room, Alahi noted. The organic chickens also were fed organically grown food like corn and soybeans free of animal byproduct. The organic feed rarely contained salmonella, while conventional feed was full of it, Alali said.
"The feed they eat is a big part of the equation," he said. "They also get more sunlight, less dust - it's a better environment."
Salmonella affects more than 140,000 Americans every year from chicken products, and about 30 die, according to the Centers for Disease Control and Prevention. The infection causes diarrhea, abdominal cramps and a fever that can last for a week.
For his research, Alali collected the chickens' feces, feed and water samples from each of the seven farms over two consecutive flocks. He found that chickens from the organic farms had a 4.3% rate of salmonella prevalence. The conventional chickens, on the other hand, were affected 28.8% of the time -- nearly seven times more.
From the April 20, 2011, Prepared Foods' Daily News.