A new Maine-based company called Covetrus Inc. is expected to make its debut Friday as a publicly traded company on the Nasdaq Stock Market exchange.

Covetrus, formed from the merger of Portland-based Vets First Choice and a division of Melville, New York-based Henry Schein Inc., would become Maine’s largest publicly traded company by far with annual revenue of about $4 billion. The state’s two largest existing publicly traded firms, Idexx Laboratories Inc. and Wex Inc., have generated revenue of $2.21 billion and $1.44 billion, respectively, in the most recent 12 months for which results are available.

Financial research and analysis firm S&P Dow Jones Indices said Wednesday in a news release that Covetrus, an animal health technology firm, would replace consulting firm The Dun & Bradstreet Corp. in its S&P MidCap 400 index beginning Friday if the stock goes public as expected.

It said S&P 500 constituent Henry Schein is spinning off its animal health division to form Covetrus with Vets First in a transaction expected to be completed Friday, while Cannae Holdings Inc. is acquiring Dun & Bradstreet in an unrelated deal also expected to close Friday.

“We are pleased that Covetrus will join the ranks of the S&P MidCap 400 Index,” said incoming Covetrus President and CEO Benjamin Shaw in a written statement. “Being recognized by the S&P reflects our strong position in the growing global animal health market. As we look forward to the launch of Covetrus, we look forward to empowering veterinarians to improve their patients’ health and thrive as small business owners.”

Post spin-off, Henry Schein would remain in the S&P 500, S&P Dow Jones said.