Drugmaker Pfizer Inc., which is spinning off its animal health business through an initial public offering, intends to sell 86.1 million shares of common stock.

New York-based Pfizer estimates the price for shares of the unit, called Zoetis (zoh-EHT'-ihs) Inc., at $22 to $25. At those prices, the IPO would raise $1.89 billion to $2.15 billion.

The business, which sells vaccines and medicines for pets and farm animals, had 2011 revenue of $4.2 billion.

That makes it the world's largest animal health business, according to a prospectus Pfizer filed with the Securities and Exchange Commission. It notes Zoetis products are sold in more than 120 countries, in five major product categories.

The unit's spinoff is part of efforts by Pfizer CEO Ian Read to revamp the world's largest drugmaker.