Pfizer Inc's plan to take its animal health unit public by selling 86.1 million shares at between $22 and $25 each could value Zoetis Inc as much as $12.5 billion.

The Wall Street Journal had last month reported that the Zoetis initial public offering (IPO) could raise about $4 billion, but at $25 per share, the offering would raise about $2.2 billion.

Pfizer, the world's largest drug maker had, in August 2012, filed for an IPO for Zoetis as part of its plan to pay off debt and focus on its core business. (See: Pfizer files IPO for animal health unit Zoetis Inc)

Under a regulatory filing with the US Securities and Exchange Commission, Pfizer had said that it would offer up to a 20-per cent stake in Zoetis in the IPO scheduled for the first half of 2013.

The IPO is scheduled to be priced on 31 January and shares are expected to begin trading on the New York Stock Exchange on 1 February.

Zoetis, which sells medicines, vaccines and other products for livestock as well as for pets, will use a dual-class share structure, with Pfizer offering all the Class A common shares in the IPO.

New York-based Pfizer had said it will exchange Class A common shares to its debt holders, who will then opt to sell the stock in the open market, but retain a 100-per cent interest in Zoetis through Class B shares that it may give to shareholders as dividend payouts.

Pfizer and Zoetis will not receive any proceeds from the IPO. Both Class A and Class B shareholders have one vote per share on all matters except the election of directors where Class B shareholders have 10 voting rights.

Zoetis, the world's largest animal health company, is a leader in the discovery, development, manufacture and commercialisation of products, including vaccines, medicines, diagnostics and genetic tests to prevent and treat disease in livestock and companion animals.

The company sells more than 300 product lines to livestock producers and veterinarians, and has operations in over 60 countries, an extensive research and development network with major research centre on four continents and strong market positions across several geographic regions, including the US, Europe, Africa and the Middle East, Canada and Latin America, and Asia-Pacific.

Around 66 per cent of its revenue comes from products used to prevent or treat conditions in livestock, with the remaining one-third coming from pet-care treatments and vaccines.

Zoetis, which competes with the animal health businesses of Merck & Co, Eli Lilly and Co, Sanofi, and Novartis, holds a 19-per cent share of an estimated $22-billion global market and contributed $4.2 billion to Pfizer's revenues in 2011.

In December 2010, it acquired veterinary diagnostics company Synbiotics Corp, in a bid to enter into the $735 million global immunodiagnostics market.

Pfizer animal health's entry into veterinary diagnostics follows a series of moves it made in 2010 to become a leader in the animal health industry, which includes expanding into the rapidly growing aquaculture segment with the acquisition of Microtek International and entry into animal health generic medicines with the acquisition of Vetnex in India.