Pfizer Inc., the world’s biggest drugmaker, took another step forward with a plan to spin off its animal health unit, registering the initial public offering with U.S. regulators.

The animal health group includes operations in North Carolina, including the former poultry health firm Embrex. Pfizer bought the company in 2006 for $155 million.

Pfizer has said it plans to sell as much as 20 percent of the new company, to be called Zoetis Inc., to raise cash.

Pfizer, based in New York, expects to give the rest of the company shares to current shareholders in a stock exchange or could hold the stock for sale later.

The regulatory filing today moves to complete the final announced piece of Chief Executive Officer Ian Read’s effort to shrink Pfizer by selling and spinning off non-drug units, which included the April sale to Vevey, Switzerland-based Nestle SA of its infant nutrition unit for $11.9 billion.

The animal health unit generated $4.23 billion last year from products used in livestock and pets.

JPMorgan Chase & Co., Bank of America Corp. and Morgan Stanley are acting as underwriters.

Juan Ramon Alaix will continue as Zoetis’s CEO, and Richard Passov will carry on as Chief Financial Officer. Frank D’Amelio, Pfizer’s CFO, will be the chairman of the board of the new company.

Regulatory filings with the Securities and Exchange Commission do not detail the size of the offering or the anticipated share price.

The New York company said it will exchange Class A common shares to debt holders, who will then sell the stock. Neither Zoetis nor Pfizer will receive proceeds. Pfizer then will keep a controlling interest in the company through Class B shares that it may give to its shareholders.

The spinoff’s name, Zoetis, derives from the word zoetic, which means “pertaining to life.” The business sells Convenia, an antibiotic for dogs and cats; Revolution, for protecting dogs and cats from fleas, heartworms and other parasites; and a cancer drug for dogs called Palladia.

It sells more than 300 product lines to livestock producers and veterinarians in about 70 countries. The business earned $245 million last year on $4.23 billion in revenue.

The spinoff is part of an ongoing makeover by Pfizer to divest nonpharmaceutical businesses and boost shareholder returns.

Last spring, Pfizer said it agreed to sell its infant nutrition business for $11.85 billion to Swiss food and drink giant Nestle SA. In the third quarter of 2011, Pfizer sold its Capsugel capsule-making business to private equity firm Kohlberg Kravis Robert & Co. for $2.38 billion in cash.

Pfizer says the Zoetis offering may happen in the first half of 2013.

(Bloomberg and The AP contributed to this report.)