Stringer . / Reuters Over 8 billion chickens were slaughtered in the U.S. in 2015.

The Humane League, a prominent animal welfare group, launched a landmark campaign this week to improve the lives (and deaths) of broiler chickens, the land animal that is consumed more than any other in the United States.

The campaign targets Aramark, a behemoth of the U.S. food services industry that runs dining operations at thousands of large institutions and last year reported over $14 billion in sales.

Among animal welfare groups, broilers (the chickens that are raised for meat, not to lay eggs) have been the proverbial elephant in the room. Their numbers are almost inconceivably vast, yet they have mostly not benefited from a wave of improvements to farm animal welfare policies announced in recent years by large meat producers and food chains.

Of the 9.2 billion land animals slaughtered in the U.S. last year, well over 8 billion of them were broiler chickens. This massive number led animal groups to pursue more attainable reforms, such as banning the practice of confining mother pigs and egg-laying hens to restrictive cages for most of their lives.

But with momentum on their side, welfare advocates are expanding their focus to the chickens we eat.

Rocco Peditto | The Humane League Demonstrators gathered outside Aramark's headquarters in Philadelphia, Pa., on Tuesday to protest the company's treatment of broiler chickens.

Overwhelmingly, the lives of these 8 billion animals are nasty, brutish and short. Today’s broiler chickens are mere babies when we eat them. They’re typically slaughtered a month and a half after being born.

They spend their brief lives ballooning to immense proportions, over six times their natural weight, a result of intense genetic selection and growth-promoting antibiotics.

As a consequence, academic and industry studies have found, they suffer. Their young tender bones often cannot handle their own body’s unnatural size. Many experience painful skeletal disorders, including deformed bones and bowed legs. Others barely walk or sit stationary.

Then they die. Standard industry practice calls for chickens to first be hung upside down by their legs, run through an electrified bath to stun them, and then have their throats slit.

That method is not entirely precise. In 2013, the Agriculture Department estimated that at least hundreds of thousands of chickens were being unintentionally boiled alive each year “because fast-moving lines fail to kill the birds before they are dropped into scalding water.”

As part of its new campaign, The Humane League made a video of archival hidden-camera footage showing the conditions at U.S. broiler chicken farms.

The video below shows physically injured or deformed chickens, and people slitting the animals’ throats. It may be disturbing to some readers.

The Humane League’s campaign calls on Aramark to make several reforms, including shifting to a breed of chicken that grows at a more natural pace, improving the broilers’ living environment and using a more humane slaughtering method involving gas.

In a statement, Aramark said it was “committed to animal welfare and sustainable sourcing practices” but announced no policy changes. “It is unfortunate that an activist organization has launched an attack campaign when we are engaged in productive dialogue with likeminded NGOs, academia and suppliers to actually resolve the problem,” the company said.

Aramark is the largest food company to be targeted over its treatment of broiler chickens. A similar campaign by the welfare group Mercy for Animals is currently pressuring the country’s largest chicken producer, Tyson Foods.

In June, one of Tyson’s competitors, Perdue Farms, announced a series of reforms similar to those being demanded of Aramark that it had developed with leading animal groups. “We’re talking about this as going back to the farm, to the way we used to do things,” said Jim Perdue, Perdue Farms’ chairman.

In an interview, The Humane League’s executive director, David Coman-Hidy, indicated that Aramark’s numerous university contracts made them an attractive target. “We feel very strongly positioned to successfully campaign against Aramark because of our connections on college campuses,” he said, referencing his group’s network of student organizers.

Earlier this year, The Humane League was one of three animal groups to receive substantial funding from Good Ventures, a foundation founded by Facebook co-founder Dustin Moskovitz and his wife, Cari Tuna.