The Humane Society of the United States is almost single-handedly changing the way farmers feed America’s appetite for bacon, ribs, holiday hams and other pork products.

Under pressure from the animal-welfare group, food industry giants such as ConAgra, Kroger, Safeway, Compass Group, Costco, McDonald’s, Burger King and Wendy’s have agreed in recent months to require their pork suppliers to phase out the use of gestation stalls for sows. The move will require producers to keep sows in pens, rather than crates, which means redesigning bars and training workers. The industry has long argued that the stalls are needed to protect sows from hurting each other, and there are concerns that the added cost ending their use will make it even harder for independent farmers to compete with corporate operations.

Gestation stalls, like conventional cages for hens, “have been scientifically researched. They have been found to provide benefits to both the animal, as well as to the farmworkers who are responsible for the care of the animals,” said Kay Johnson Smith, president and CEO of the Animal Agriculture Alliance.

But Temple Grandin, a renowned expert on animal welfare respected both by industry and activists, says the way sows and hens are housed is by far the two biggest issues and that change is inevitable in both. Another issue, docking the tails of dairy cattle, is being eliminated, she says.

“The public is just not going to accept sow stalls,” says Grandin, who has advised a variety of companies, including McDonald’s.