BlackRock and other big McDonald's shareholders are backing the company in a boardroom vote, putting the fast-food chain on course to defeat investor Carl Icahn in his campaign over animal welfare, sources said on Wednesday.

Icahn, a billionaire who owns roughly $50,000 worth of McDonald's stock, nominated two director candidates to push the company to make good on a decade-old promise to stop buying pork by the end of this year from suppliers that house the animals in crates. He has said confining the pigs in crates during their pregnancy is inhumane and sought to shine a spotlight on the practice more broadly.

Index fund BlackRock, whose 4.6% stake ranks it as McDonald's third-largest investor, has cast its votes for the company, two people familiar with the voting said.

Vanguard, which is McDonald's biggest shareholder, had also voted some of its shares for the company's directors, according to earlier vote tallies, another source said.

Investors have time to change their votes until the annual meeting scheduled for Thursday morning, but people familiar with the voting say it is very likely McDonald's will win.

A representative for McDonald's declined to comment and a representative for Icahn did not immediately respond to a request for comment.

The final vote would end, for now, a battle between one of America's most successful activist investors and one of the world's most iconic brands over how McDonald's sources its pork.

McDonald's says it has worked to change its pork sourcing and that it cares about the health and welfare of the animals in its supply chain but called Icahn's demands "completely unfeasible."

BlackRock's vote is a blow for Icahn who had sought to appeal to the big index funds, including Vanguard and State Street, as they often pledge to pay particular attention to environmental, social and governance issues. He expressed concern they are not prioritizing animal welfare.

Proxy advisory firms Institutional Shareholder Services and Glass Lewis recommended that shareholders back the company's directors, arguing that Icahn had failed to make a compelling case for change and that his nominees lacked the necessary qualifications to serve on McDonald's board.

But both firms, whose recommendations are widely followed by investors, said Icahn had raised awareness for animal rights.