FREDERICKSBURG, Pa. — 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.

Oregano lies loose in trays and tied into bunches on tabletops and counters, and a big, blue drum that held oregano oil stands in the corner. “Have you ever tried oregano tea?” Mr. Sechler asked, mashing leaves between his broad fingers.

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.