LONDON (Reuters) - Papa John’s International (PZZA.O) on Tuesday said it had signed up to a pledge that commits restaurant chains to cage-free eggs, part of an industry campaign aimed at drawing up tougher animal welfare rules.

FILE PHOTO: The logo of Papa John's Pizza is seen on the entrance of their PizzaRev restaurant in downtown Rome, Italy, September 23, 2018. REUTERS/Alessandro Bianchi/File Photo

The global campaign, launched last month by humane-food charity Humane Society International (HSI), comes amid growing scrutiny of the treatment of chickens and other animals used to feed growing appetites for cheaper frozen pizza.

“We’re thrilled to be a part of P.J.’s campaign as well as the thousands of other businesses across the globe pledging to source cage-free eggs,” Steve Ritchie, Chief Operations Officer for Papa John’s, said in a statement.

As part of its pledge, the pizza chain said that in the next two years it would phase out buying chicken breasts from farms that don’t provide room for its chickens to stand, lie down, turn around and fully extend their limbs.

The company, which controls 14 percent of the U.S. pizza delivery market, said it would convert its supply chain to free-range eggs by the end of 2022.

HSI International said it had signed up more than 70 companies since the campaign began on Jan. 1, including Domino’s Pizza (DPZ.N), Pizza Hut, Subway, Starbucks (SBUX.O), McDonald’s (MCD.N) and Burger King.

It said it plans to encourage even more of the sector’s biggest brands, which together account for more than 50 percent of the total market, to join the initiative.

Analysts have long suggested that a cage-free standard would benefit pizza chains by boosting the value of the unit they sell, potentially leading to stronger sales growth.

For the first 11 months of last year, Brinker International’s (EAT.N) Pizza Hut chain, the second-biggest U.S. pizza delivery chain, sold nearly as many units as Papa John’s.

However, Papa John’s is expected to put further pressure on Pizza Hut as it brings new leadership in.