In an article in Environmental Science & Technology, a study was done by a team of researchers to detect antimicrobial residue in feather meal.
Antimicrobials used in poultry production n have the potential to amass in poultry feathers but available data are scarce. Here is what happens. Poultry, (for example, chickens), are slaughtered and the feathers removed. The feathers are converted into further meal and sold as fertilizer and animal feed.
Since the animals are fed antimicrobials like Cipro, the drugs could enter into the human food supply. This study analyzed the meal for 59 pharmaceuticals and personal care products and found that all samples tested positive. Caffeine and acetaminophen were detected in 10 of 12 samples.
The study also showed that a certain types of E.coli were inhibited while other types were not. More studies are needed for potential risk factors to consumers.