PORTLAND — Immucell Corp., a Portland biotechnology firm, is one step closer to selling a product to treat udder infections in dairy cows.

A ruling by the U.S. Food and Drug Administration means that farmers who treat dairy cows with nisin, the chemical in Immucell’s Mast Out product, do not need to discard the milk during treatment.

Immucell has been developing Mast Out for 10 years. The FDA has required that farmers treating cows discard the cow’s milk.

“ImmuCell management believes that this would be a significant competitive advantage differentiating Mast Out from all other intramammary antibiotics. Market acceptance of this novel product, as a tool capable of revolutionizing the way that mastitis is treated, is critically dependent upon achieving this zero milk discard claim,” said the release.

The decision must still receive New Animal Drug Application approval by the U.S. Food and Drug Administration, and other approvals.