As an undergraduate student, McElroy and her graduate advisor got the idea of feeding hot pepper oil to chickens while they and a graduate student from Mexico were eating hamburgers filled with hot sauce and covered with layers of jalapeno peppers. When they wondered aloud why people like spicy foods even though they often cause a runny nose, watery eyes, and other ill effects, the Mexican student said that people in his country believe that hot foods and spices provide protection from disease.
Their laboratory quickly made the jump from humans to poultry, and hypothesized that a diet that included some form of hot peppers might protect broilers and other commercial poultry from intestinal disease.
The research began with purchasing 1,530 commercial meat chicks, dividing them into three groups, and feeding each group a standard corn and soybean meal-based diet for 42 days. McElroy fed the plain feed to the first group, but added five parts per million of pure capsaicin to the feed of the second group, and 20 parts per million to the third group’s feed.
She then administered Salmonella enteritidis to the chicks at 21, 28, and 42 days of age. She found that both the low and the high level of capsaicin increased resistance to the Salmonella without adversely affecting feed consumption, weight gain, or the taste of the chicken when cooked.
"What we saw from our initial microscopic evaluation is that the capsaicin appears to cause a very mild inflammation in the intestines," McElroy says.
One theory she’s investigating is the possibility that the presence of the capsaicin-induced inflammation might make it more difficult for the Salmonella to bind to the intestinal cells and, from there, to branch out to invade the blood, liver, and spleen.
"Or," she says, "it may be that the capsaicin acts on the intestine to recruit immune cells, which then fight off the Salmonella."
Her current research is designed to evaluate any observable effects of capsaicin directly on Salmonella in laboratory conditions, the effects of capsaicin on the intestinal environment, and the most economical scheme of feeding capsaicin to commercial poultry.
McElroy says that Salmonella typically results in little to no observable illness in chickens, but it is a disease of concern to the industry due to its ability to cause human illness. In a poultry house, it’s spread from bird to bird or through the feeders and water. From there, it may move into the processing plant, where it can cross contaminate other birds, however the industry implements procedures both on the farm and in the processing plant to minimize this risk.
"I think there’s probably less Salmonella in our poultry today than there was in the past, because the industry has taken preventative measures," she says. "But it would be a real breakthrough if we could find a way to reduce levels even further, without the use of antibiotics."
The poultry that McElroy has worked with seem to have no objections to the taste or sting of the capsaicin. She theorizes that chickens and other birds may have evolved so that their taste receptors adapted to allow them to eat the colorful pods. "Birds in the wild are very attracted to bright colors, and they spread the seeds by breaking up the pods," she said.
Rodents, on the other hand, have an aversion to the hot seeds. "Feeding poultry feed to which capsaicin has been added could be very beneficial in poultry houses," she says. "Rodents love to get into poultry house, where they eat the feed, destroy buildings, and spread Salmonella and other diseases. If the food is unappetizing to them, it might keep them away."
Snyder Seed, a New York-based company, developed a line of wild birdseed coated with chili pepper oil, which they call Hot Pepper Treat. "Squirrels and other rodents won’t eat the food," McElroy says.
"If we can prove that feeding capsaicin to birds does reduce Salmonella in a commercial poultry-production situation, it would provide a non-antibiotic way of reducing food-borne pathogens," she says. "Consumers want an antibiotic-free product, and this may provide the answer."
McElroy’s research is partially funded with a grant from the Virginia Agricultural Council.
Researcher:
Audrey McElroy, Assistant Professor
Animal and Poultry Science
Virginia Tech
540-231-8750
amcelroy@vt.edu