Sales were down 20 percent in the third quarter for Portland-based animal health products maker ImmuCell Corp., the company reported Thursday.

ImmuCell, which makes bovine health products for the dairy and beef industries, reported revenue of $2 million for the quarter, down from about $2.5 million in the third quarter of 2015. Net income for the third quarter was $35,000, a decrease of about 90 percent from $351,000 during the same period of 2015.

ImmuCell, a publicly held company that trades on the Nasdaq exchange under the symbol ICCC, said the decrease in sales of its flagship product, First Defense, was due in part to a prolonged period in which the company could not keep up with customer demand, creating a backlog of orders and causing some customers to switch to a competitor. The company has since increased its production capacity and the backlog has been eliminated, it said.

Also, ImmuCell said a competitor that had left the market in 2015 returned, causing some former customers who had switched to ImmuCell to resume using the competitor’s products.

ImmuCell plans to diversify its product offerings with a new cure for bovine mastitis for which it is currently seeking U.S. Food and Drug Administration approval. A new facility to produce that product, called Mast Out, is under construction.