In the realm of animal protection, the chickens that we eat, known as broilers, have been the proverbial elephant in the room.

Their numbers are almost inconceivably vast. Roughly 9 billion chickens are slaughtered every year in the United States, making up well over 90 percent of the land animals killed for food.

Yet broiler chickens 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.

On Thursday, that changed. Within an hour of each other, two of the world’s largest food services companies, Compass Group USA and Aramark, announced sweeping new welfare improvements for broiler chickens in their supply chains.

Both companies manage dining operations at thousands of hospitals, universities and other large institutions. Together, their new policies will improve the wellbeing of over 100 million animals every year.

“I’m not aware of another day in U.S. history that produced policies that affected more animals than the ones announced today,” said Josh Balk, food policy director at the Humane Society of the United States. “If there is one, I’m not aware of it. I can’t think of one that comes close.”

Lester Lefkowitz via Getty Images

As it stands, the lives of broiler chickens in the U.S. are nasty, brutish and short. They are mere babies when we eat them, slaughtered about six weeks after birth.

They spend their brief lives ballooning to immense proportions, over six times their natural weight, a result of intense genetic selection. (In human terms, this is akin to a 160-pound adult male bred to weigh about a thousand pounds.)

As a consequence, academic and industry studies have found, they suffer. Their underdeveloped bones often cannot handle their own body’s unnatural mass. Many experience painful skeletal disorders and bowed or fractured legs. These birds will barely walk, or sit stationary for much of their lives.

They’re housed in barren, tightly packed warehouses with limited natural light and few if any enrichments, like hay or perches, that would allow them to perform basic instinctual behaviors.

And then they’re off to the slaughterhouse, where extensive research has found that the electric stunning method used by U.S. processors is not consistently effective. As a result, scientists say, hundreds of millions of chickens at minimum likely experience intense suffering when they are slaughtered.

The most extensive footage of modern broiler farming comes from a former contract farmer for Perdue, one of the largest U.S. poultry companies, who became a whistleblower and opened his farm to cameras a few years ago. In June, Perdue became the first major poultry company to announce its own welfare improvements for broiler chickens.

In their announcements, both Compass Group USA and Aramark committed to reforming each of these practices in their supply chains.

First, they pledged to shift to healthier genetic strains of broiler chickens that grow more slowly. The strains will be approved by an independent animal welfare certification group, the Global Animal Partnership.

Second, they said they’ll require suppliers to provide new minimum space requirements for their birds and introduce housing enrichments, including hay bales, perches and natural light.

Finally, they agreed to order suppliers to replace electric stunning with a slaughter method that is overwhelmingly viewed as more humane. Under the alternative system, known as “controlled atmosphere killing,” birds are exposed to a rising concentration of gas (typically carbon dioxide) until they lose consciousness.

Balk said it was remarkable for such a major policy shift to first be adopted by some of the largest poultry buyers in the country.

“This is going to propel the industry to start making these changes overall,” he said. “Every policy change brings about another policy change. The suppliers, the large poultry companies, will have to shift their operations to meet the demand of Compass and Aramark.”

Nico Pitney is a senior editor at The Huffington Post. Tips? Feedback? Email him at nico.pitney [at] .