Feeding chickens a mixture of plant-based oils in their water may become an effective method of reducing Salmonella contamination in chicken products, according to experimental studies by researchers at the University of Georgia in Griffin. The studies, published in the journals Food Control and Poultry Science, found that an essential oil treatment significantly reduced the perfcentage of Salmonella bacteria in a chicken’s crop — the organ at the base of the esophagus that stores food. The crop is one of two organs often colonized by Salmonella, the other being the cecum, a part of the large intestine.

Dr. Walid Alali (photo courtesy of University of Georgia College of Agricultural and Environmental Sciences)
Chickens that consumed the oil mixture harbored fewer Salmonella bacteria in their crop, but nearly similar percentages in their ceca when compared to chickens that simply drank water. During slaughter and processing, chicken meat can become contaminated with pathogenic bacteria if either of those two organs becomes ruptured. Considering that the oil treatment does little to reduce Salmonella in the cecum, it might appear wishful to think it could significantly reduce contamination in the slaughterhouse. The upshot, however, is that a chicken’s crop is roughly 86 times more likely to be ruptured during slaughter than the cecum. The studies’ lead author, Walid Alali, Ph.D., told Food Safety News he has not heard of any studies estimating the percentage of carcasses contaminated by rupturing of the crop versus the cecum. But the hope is that Salmonella reductions in the crop alone may be enough to stave off considerable amounts of contamination during processing, Alali said. Alali’s studies used a commercial oil mixture known as “mix-oil,” an Italian-made product first marketed in 2004 to improve livestock health. It was never intended to treat pathogens, but numerous studies demonstrate the antimicrobial characteristics of essential oils, Alali said. Some researchers and farmers have tried using essential oils to control pathogens in the past, though this marks the first time oils have been blended into the water. Others add organic acids into the water for the same purpose. The advantage to distributing oils via water as opposed to feed comes when considering a certain practice in chicken farming known as the “withdrawal period”: Chickens are typically denied feed for the last 8 to 12 hours of their life before transport to slaughter and are only left with water to drink. Naturally, the chickens get hungry in that much time. They start pecking at anything that might look like food — including litter, which might be contaminated with Salmonella. “If the oils are in the feed, the chickens receive nothing to control Salmonella once the food is taken away,” Alali said. “If the oil is in the water, we’re controlling Salmonella until they are transported to the slaughterhouse.” The mix-oil treatment has also shown to improve the birds’ overall health. Weight gain, feed conversion ratios and mortality rates all improved with the addition of mix-oil to the study flock’s water source. Thus far, Alali’s treatment has not been tested outside a controlled research environment. The next step is to advance the study to a large-scale commercial farm. “At some point, we’ll try it at the large scale,” he said. “If we have chickens ready to go to supermarkets, we can determine if we reduce Salmonella numbers all the way from the farm to processing to the grocery shelf.” Alali also said he plans to further study the mechanism of how the oil mixture works to kill Salmonella. The mixture consists of oils derived from thyme, oregano and eucalyptol. Raising a flock of 20,000 chickens to slaughter weight using the mix-oil treatment should cost roughly $500. “People are getting excited about the treatment because it uses water as a means of delivery,” Alali said. “It’s a lot easier to treat chickens that way than in the feed.”