Animal Equality Hens at a factory farm in Mexico are forced to molt to improve egg production.

An animal protection group has released graphic undercover footage of an industrial chicken farm in Mexico, where hens spend their lives trapped in minuscule cages and are intentionally starved to induce egg production.

The video, produced by Animal Equality, kicks off a broad new effort to end some of the cruelest practices of modern animal agriculture in countries outside the United States. It is funded in large part by Facebook co-founder Dustin Moskovitz and his wife Cari Tuna through the Open Philanthropy Project.

In the undercover video, egg-laying hens are held in wire cages so small they cannot stretch their limbs, let alone perform basic instinctual behavior. Many of the hens are filthy, covered in other birds’ droppings, and confined with other chickens that are dead or dying.

They are also subjected to “forced molting,” a practice to induce stress in hens by depriving them of light and starving them for days on end. The stress causes birds to shed and regrow their feathers. They temporarily stop laying eggs, providing their reproductive systems time to recuperate, and subsequently they produce better quality eggs.

WARNING: The video below shows graphic content including injured and deceased chickens. It may be disturbing to some viewers.

Roughly five billion egg-laying chickens are raised globally each year, and the vast majority spend their lives confined in these small enclosures, called battery cages.

Recent campaigns to end the use of battery cages in the U.S. have been the most successful in the history of farm animal welfare, advocates say. In the last two years alone, every major grocery and fast-food chain in the country has committed to selling only cage-free eggs.

Aiming to replicate this success abroad, the Open Philanthropy Project last week announced nearly $4 million in grants to animal groups to pursue international cage-free campaigns.

“A lot of the factory farming practices that cause so much suffering to animals in the U.S. have now been exported around the globe,” said Lewis Bollard, who oversees the project’s farm animal welfare grants. “We don’t want to make progress in the U.S. only to see it undermined by a continuation and expansion of the practices abroad.”

Latin America is a major focus. Mexico and Brazil are two of the world’s leading egg-producing countries and conditions for hens there are even worse than in the United States.

Forced molting remains standard practice in Latin America (it is uncommon in the U.S. and illegal in Europe), and egg-laying chickens are packed about 30 percent more tightly than in U.S. factory farms. A typical hen raised in Mexico will live out its one- or two-year existence within the space of 48 square inches.

Sharon Nunez, executive director of Animal Equality, said the undercover video was the Mexican public’s first glimpse inside their country’s factory farms.

Animal Equality is not identifying food companies that purchase eggs from the facility shown in the video. Rather, Nunez said, the footage would first be used to privately pressure companies to voluntarily adopt new welfare policies.

Animal Equality Hens at a factory farm in Mexico are forced to molt to improve egg production.

Beyond Latin America, the Open Philanthropy Project is funding new advocacy work in India, Japan and Germany, as well as campaigns targeting multinational food companies headquartered in Europe. The project targets high-impact causes that aren’t getting sufficient funding from other charitable donors.

The world’s largest and second-largest food services corporations ― Compass Group and Sodexo ― each recently announced timelines for converting their entire global operations to cage-free eggs.

And two weeks ago, Burger King became the first major fast-food brand to commit to using only cage-free eggs in its Latin America supply chain.