Dr. Stephen Sundlof, director of the FDA's Center for Veterinary Medicine, told Reuters that practice was one of several regulators were reviewing as they consider whether to tighten the shield against the illness. So far, neither mad cow disease nor its deadly human form have been found in the United States. Federal rules that took effect in 1997 prohibit feeding cattle or sheep with protein from animals that are potential carriers of mad cow or a related illness. Feeding contaminated animal remains is blamed for spreading the disease to cows throughout Europe.
Experts believe people get the brain-wasting illness by eating contaminated meat products.
Now, litter containing waste from chickens legally can be processed and fed to cattle under some circumstances, Sundlof said. Some have questioned whether chickens that ate material prohibited for cattle could recycle the banned byproducts back to cows that ate their litter. The abnormal proteins believed to cause mad cow disease have proven resilient, and it is unknown whether a chicken's digestive tract could kill them. Sundlof said in an interview. In remarks to a public meeting regarding mad cow, also known as bovine spongiform encephalopathy, Sundlof said regulators were re-evaluating other practices now exempt from cattle feed bans.