This sounds interesting:
The smell of oregano wafting from Scott Sechler’s office is so strong that anyone visiting Bell & Evans these days could be forgiven for wondering whether Mr. Sechler has forsaken the production of chicken and gone into pizza.
Off and on over the last three years or so, his chickens have been eating a specially milled diet laced with oregano oil and a touch of cinnamon. Mr. Sechler swears by the concoction as a way to fight off bacterial diseases that plague meat and poultry producers without resorting to antibiotics, which some experts say can be detrimental to the humans who eat the meat. Products at Bell & Evans, based in this town about 30 miles east of Harrisburg, have long been free of antibiotics, contributing to the company’s financial success as consumers have demanded purer foods.
But Mr. Sechler said that nothing he had used as a substitute in the past worked as well as oregano oil.
UPDATE: Gavura’s post was from May of 2011, and the materials he cites are of course from before 2011, the latest one being a 2010 review of studies from past years. This October 2011 study indicates that 3% oregano oil helps to fight against Staphlococcus aureus infections. To my mind this would fit in with the results of a 2001 study that seems to indicate that oregano oil as extracted from the plant works better at fighting bacteria than does carvacrol alone, which is thought to be the chief antibacterial agent in oregano oil. The other chemicals in oregano oil apparently possess antibacterial properties that work with carvacrol’s to reduce bacteria in the test subjects.