The animal-welfare movement is on the verge of ending confinement practices that keep pigs in gestation crates and hens in tight cages. What comes next?

“Broilers or bust,” declares Matt Prescott, senior food policy director for the Humane Society of the United States (HSUS).

Other activists agree: Their top priority is alleviating the suffering of the billions of broiler chickens that are raised for meat, as they sense victory in the decade-long, hard-fought battles to liberate pigs from their crates and hens from their cages.

Campaigns on behalf of broiler chickens could prove harder to win. That’s because the issues involved–genetic breeding, stocking levels, access to light and slaughter practices–are core to the chicken industry’s current business model, which aims to grow chickens as big and as fast as possible. These issues are also harder to communicate than the either-or questions of whether pigs should be confined in crates or hens in cages.

On the other hand, the animal-welfare movement has proven to be resourceful, working on college campuses, in the political arena and in the courts; attacking some companies and forging partnerships with others; investing in plant-based protein alternatives and even trying to persuade Wall Street bankers to consider the reputation risks posed by factory farms.

Broiler chicken issues were front and center at an HSUS conference last weekend in Washington on the future of food. (I moderated a panel of activists.) David Coman-Hidy of The Humane League, Leah Garces of Compassion in World Farming, Erica Meier of Compassion Over Killing and Nathan Runkle of Mercy for Animals all said they had begun or soon would launch efforts to improve the conditions of broiler chickens.

Meantime, the Open Philanthropy Project expects to make a series of grants to support broiler chicken campaigns, according to Lewis Bollard, who oversees its grant-making on animal issues. Open Philanthropy is a project of GiveWell and Good Ventures, the philanthropic arm of billionaires Cari Tuna and Dustin Moskovitz, a Facebook co-founder.

“It’s the numbers that direct you to broiler chickens,” Bollard explains. Between 8 and 9 billion broiler chickens are raised and slaughtered every year in the US, and about 1.5 billion are alive at any given time. By comparison, about 300 million laying hens are at work at any given time. “It’s also the case that broiler chickens are horribly treated,” Bollard says.

“Trapped in a genetic cage”

Breeding is a key issue. The Humane League, which just launched a campaign against food-service company Aramark, says chickens are “bred to grow so unnaturally large and fast that they often develop crippling leg disorders, heart failures, respiratory problems and lameness.” They grow to maturity in just 48 days, less than half of the time it took a century ago, the group says.

Leah Garces of Compassion in World Farming says broiler chickens “are trapped in a genetic cage. Their body is their cage.”

As if that weren’t enough, the vast majority of broiler chickens live indoors in crowded and filthy conditions. They are usually electrically stunned before being killed, but some are still alive when their throats are slit open and plunged into vats of scalding water.

David Coman-Hidy of The Humane League says Aramark is vulnerable to a campaign because the company operate a lot of college cafeterias. As a grass-roots group, The Humane League has paid staff in 11 US cities and organizers on 42 college campuses who are able to rally their troops. “We want Aramark to be hearing from every single (college) client saying, make this go away,” Coman-Hidy says.

In response, Aramark says it has an “industry leading” animal welfare policy. In fact, its policies on eggs and pork have won plaudits from HSUS, which has worked with Aramark for years. But with respect to broiler chickens, Aramark says only that it will work with suppliers to address issues related to “genetic selection for fast growth of broiler chickens” and support the elimination of slaughtering systems that use live dumping and shackling, without setting targets or timetables. Aramark also says, accurately, that “producing sustainably sourced broiler chickens is currently a challenge for the entire poultry and food industry, not just Aramark.” HSUS’s Josh Balk tells me: “On broilers, they haven’t made a commitment yet, but I’m cautiously optimistic they’ll do so in the near future.”

Several companies have gone further, the activists say. Working with the Global Animal Partnership, Whole Foods Market has pledged to implement new broiler-chicken welfare standards and move away from fast-growth breeds of chicken by 2024.

While overt cruelty to individual chickens is against federal law, there’s virtually no regulation of the way broiler chickens are bred, raised or killed. But, nlike the campaigns for cage-free eggs or against gestation crates, which were brought to voters in a number of states — including Massachusetts next month — the broiler chicken issue isn’t deemed ready for the legislative or political arena.

To set the stage for corporate and political action, the animal-welfare groups want to raise awareness of the suffering that is baked into chicken wings or fast-food nuggets. Among other things, the groups will try to infiltrate chicken farms with hidden cameras. “Undercover investigations are going to be really crucial,” said Nathan Runkle of Mercy for Animals. Because they can be spread widely via social media, undercover images expose conditions on factory farms that would otherwise remain hidden.

As Paul Shapiro, HSUS’s vice president for farm animal protection, puts it: “People eat meat with their eyes squeezed shut.” When that changes, so will the way we treat farm animals.