Voters in Massachusetts will decide next month whether to pass a far-reaching law to protect farm animals from extreme confinement, and polling suggests they will approve it overwhelmingly.

The ballot measure targets practices that severely constrain animals for virtually their entire lives, including the use of veal crates for baby calves, gestation crates for mother pigs and battery cages for egg-laying hens.

Eleven states have passed laws banning one or more of those practices. The Massachusetts measure would prohibit all three, and then go further. It would also bar the sale of meat and eggs produced using those methods, even if the animals were farmed outside the state.

Two independent polls released in the last month show likely voters supporting the measure by wide margins ― 41 points and 61 points, respectively. And while several agribusiness groups oppose the initiative, they’ve spent little to campaign against it.

Mercy for Animals Mother pigs will often spend most of their lives in gestation crates, unable to turn around or lie down naturally, let alone practice typical social behaviors.

That law applies exclusively to the moment when livestock are slaughtered; it says nothing about how farm animals should be treated during the rest of their lives, from birth onward. It also completely exempts chickens and other animals that make up over 90 percent of the animals slaughtered.

For example, it is perfectly legal for female pigs, among the most cognitively complex and socially sophisticated animals, to be repeatedly impregnated and shut in small crates for most of their lives, unable to exhibit natural social behavior or even to turn around.

But these corporate reforms are entirely voluntary. Measures like the one in Massachusetts are needed to cement those changes, said Paul Shapiro, head of the farm animal welfare campaign at the Humane Society of the United States, which has spearheaded the ballot drive.

California is the only state that currently bans the sale of food products over animal cruelty concerns, and its law applies only to eggs from caged hens. The Massachusetts measure, which extends to veal and pork, would be the broadest of its kind in the U.S. and probably the world, Shapiro said.

With momentum on their side, advocates are also increasingly focused on campaigns that go beyond combatting extreme confinement of animals in the United States.

Two groups have launched campaigns this year aiming to reform how food companies raise the over 8 billion chickens that Americans eat annually.

These chickens, called broilers, aren’t kept in cages like the hens that lay eggs, but there are other concerns. They are genetically modified to grow at such an aggressive pace that their bodies often break down, and current slaughter methods lead to hundreds of thousands of birds being boiled alive every year.

Also, this week, the Open Philanthropy Project funded by Facebook co-founder Dustin Moskovitz and his wife Cari Tuna announced it would spend $3.6 million to support cage-free campaigns outside of the United States.