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Alamy stock photo by Stephen Bay

It is a common practice in the United States to keep sows in gestation crates for the duration of their pregnancy, which is about four months. Measuring 7 feet by 2 feet, the space does not afford room for the animal to walk or turn around.

When passed by popular vote in California in 2018, Proposition 12 was considered a landmark animal rights law.

The legislation establishes minimum space requirements for pregnant pigs and prohibits selling pork raised on farms that don't comply. This restriction effectively bans the use of gestation crates, also called gestation stalls, which are confined spaces with metal bars used to house pregnant sows. Typically around 7 feet by 2 feet, they are too small for sows to turn around in, much less walk or move freely. The laws also included minimum space requirements for egg-laying hens and calves raised for veal.

California wasn't the first or only jurisdiction to ban gestation crates. At least 10 other states have done so, as have several countries. But the law in California, like one approved by voters in Massachusetts in 2016, applies to all pork sold within the state, no matter its origin.

Owing to the size of the California market — the state is home to 11.5% of the United States population — the 2018 law was opposed by the pork industry, as producers across the country were affected. Iowa, Minnesota and North Carolina are the nation's top hog-producing states.

The National Pork Producers Council sued California. The legal battle that followed ended in 2023 with a U.S. Supreme Court opinion affirming — in a 5-4 decision — California's right to pass such a law. The majority opinion stated that while the law had extraterritorial effects, it didn't intentionally discriminate against any other state nor place an insurmountable burden upon them.

"What goods belong in our stores?" the court opinion, written by Justice Neil Gorsuch, begins. "While the Constitution addresses many weighty issues, the type of pork chops California merchants may sell is not on that list."

Instead of the dust settling on this issue, the arena for the fight simply changed. Now Congress is considering language in the upcoming farm bill that would gut the gestation crate laws in California and Massachusetts by prohibiting state laws from placing a condition on the production of livestock in other jurisdictions.

The farm bill is a large package of legislation passed approximately every five years. Its contents impact every part of the food system — farm subsidies, supplemental nutrition assistance and more.

Several aspects of the mega-bill are directly pertinent to veterinarians. For example, the Veterinary Services Grant Program, which supports veterinarians in rural areas short on care, is authorized by the legislation.

As Congress takes steps to finalize the country's next farm bill, veterinarians are speaking up about sow housing, with members of the profession falling on opposite sides of the issue.

Veterinarians debate sow welfare

Gestation crates have been used in pork production since the late 1960s and became mainstream in the 1990s. Sows live in the crates from the time of insemination until a few days before they are anticipated to give birth, about four months. Then, they're moved to farrowing crates. These housing units look similar to gestation crates — stalls with metal bars — but are slightly larger to allow room for the piglets to nurse. (Farrowing crates are not regulated under the California and Massachusetts minimum space laws.)

Sows may be inseminated again as soon as a few days after their piglets are weaned, according to a write-up by the U.S. Food and Drug Administration and the Western Institute for Food Safety and Security at the University of California, Davis. A sow can have at least two pregnancies per year, resulting in her spending eight or more months annually in a gestation crate. While the natural lifespan of a pig is 15 to 20 years, many commercial sows are culled after three to five litters, when they are a few years old.

A survey of hog farms by the USDA in 2021 found 57.5% housed sows in individual stalls. The share of farms using this type of housing varied by their size. The housing type was most apt to be used by large operations, at 61%, followed by small operations at 48%. Medium-sized operations were the least likely to use them, at 18%. Large farms were defined as those with 500 or more breeding females, medium as 250 to 499 breeding females, and small as those with fewer than 250 breeding females.

Producers might favor gestation crates to save space, manage individual sows' food intake and reduce physical conflict among the herd. For the sows' part, research has shown that those kept in such confinement display behaviors associated with frustration, stress and boredom, such as biting the bars of their cages. One study, by University of Pennsylvania School of Veterinary Medicine researchers, indicated that sows pushed their bodies against the bars 41 to 173 times per hour in attempts to exit.

According to a fact sheet by the Humane Society Veterinary Medical Association, gestation crates can lead to other adverse health effects for sows, such as urinary tract infections from sitting in their own excrement. If their legs slip through the bars into a neighbor's crate, they risk injury by the neighbor; pregnant sows weigh hundreds of pounds.

The primary alternative to gestation crates is group housing, wherein multiple sows share one larger space. California's Proposition 12 specifically mandates 24 square feet of room per animal, whereas Massachusetts' Question 3 outlaws housing types that "prevent a covered animal from lying down, standing up, fully extending the animal's limbs, or turning around freely."

The American Association of Swine Veterinarians (AASV) pushes back on the idea that group housing is always better for welfare. Dr. Abbey Canon, director of public health and communications for the AASV, told the VIN News Service in an email that individual stalls and group pens are both valuable options for sow housing, and categorically banning one will likely harm, rather than improve, animal well-being.

"Which of them is best to use, in what proportions, and at what times in a sow's reproductive cycle, are questions that depend on the individual circumstances of a farm and its herd," Canon said. "Maximizing animal health and welfare therefore requires housing arrangements for sows to be determined on a case-by-case basis, by farmers and veterinarians considering all the circumstances of each individual herd and farm."

When the Proposition 12 case went to the Supreme Court, the AASV wrote in an amicus brief that individual housing addressed certain aggressive behaviors witnessed in group pens, such as vulva biting and competition for food.

Dr. Gwendolen Reyes-Illg, president and co-executive director of the Veterinary Association for Farm Animal Welfare, a nonprofit education and advocacy organization, counters that there are techniques for minimizing aggression in the group. Conflict-reducing factors include pen size and layout, access to enrichment opportunities and diets formulated to quell hunger.

Moreover, she points out, California's law doesn't mandate group housing; it requires a minimum amount of space. If a sow needs to be individually housed to manage aggression, she said, that is still Proposition 12-compliant, as long as the animal has enough room to move around.

"Prop. 12 in particular is about a space requirement, so there's enough flexibility in there that if you needed to have a sow be by herself for some period of time to recover from an illness or something like that, you have the flexibility to do that," she said.

Reyes-Illg was a co-author of a separate amicus brief to the Supreme Court in support of Proposition 12, which was signed by nearly 400 veterinarians.

In the AASV's brief, the organization stated that while sow aggression cannot be eliminated in group pens, it can be minimized with proper husbandry techniques. However, it states that doing so can require extensive planning and training for farm staff.

"The best solution for animal welfare is for each team of farmers and veterinarians to have flexibility to determine the housing arrangements that are best for their animals in their circumstances," Canon wrote. "Because Proposition 12 would take away that flexibility, it places at risk the well-being of many animals."

Legislation 'patchwork' at issue

While sow welfare is the original cornerstone of the gestation crate debate, the issue is complicated by its interstate trade implications.

This aspect has become so central in the debate that the draft farm bill wording that would defang these laws, Section 12006, doesn't mention gestation crates at all. It reads, in part:

"Producers of covered livestock have a federal right to raise and market their covered livestock in interstate commerce and therefore no state or subdivision thereof may enact or enforce, directly or indirectly, a condition or standard on the production of covered livestock other than for covered livestock physically raised in such state or subdivision."

If passed as written, the language negates any state law that puts a condition of sale on livestock products from another state. It would not affect any state laws that ban gestation crate use within their own jurisdictions.

"Up to 50 different state laws mean inconsistent regulations that create uncertainty, increase costs in animal care, and complicate efforts to maintain high standards of animal care," Canon said by email.

The American Veterinary Medical Association, in a 2025 policy on sow housing, walks a balance between maintaining individual crates as an option and greater adoption of group housing. In a statement about the policy, it says that "the AVMA encourages current movement within the swine industry toward group housing, while also acknowledging the challenges and benefits that are associated with this change."

On the proposed farm bill language, however, the AVMA is unambiguously in favor. In a letter dated April 20 to the House Committee on Agriculture, it calls Section 12006 a "solution" to Proposition 12.

"This kind of legislation will create a patchwork of regulations that are often not scientifically based, could impact biosecurity, and would be cost prohibitive and cumbersome for veterinarians and their producer clients to navigate," said the letter, signed by Dr. Janet Donlin, chief executive officer of the AVMA. "Ensuring good animal health and welfare requires a veterinarian to have the freedom and authority to recommend the best course of action for each unique situation."

The organization representing veterinarians in Massachusetts takes the opposite tack on the Section 12006 language. Jamie Falzone, executive director of the Massachusetts Veterinary Medical Association (MVMA), said the organization's executive board formally registered opposition.

Their reasons are twofold: They are concerned about sow welfare, and they didn't want to go against Massachusetts voters. The ballot initiative known as Question 3 passed with 77.6% of the vote.

"From our perspective, because we haven't been hearing any uproar about it all, it feels like this is what Massachusetts wants," Falzone said.

A letter sent by the MVMA to their state representatives in Congress reads in part:

"Claims that the veterinary profession supports the preemption of state laws like Question 3 and Proposition 12 (as passed by California) are false. Transitions to group housing systems for pregnant sows have safely and successfully occurred in our state, and while good or adequate welfare is not guaranteed under these systems, research has identified the essential elements to ensure they do."

The California Veterinary Medical Association (CVMA) did not take a position on Proposition 12, and it generally defers to the AVMA on federal legislation, said Dr. Grant Miller, director of regulatory affairs. He referred VIN News to the CVMA's published policies on farm animal confinement and sow housing. The latter states that sows should have an environment that allows them to exhibit their normal behavior: "Sows require adequate mobility to allow for the sow to turn around comfortably and to assume normal postures ... We do recognize that group housing of sows does require a higher level of animal husbandry to assure the good health and welfare of the individual animal."

What's next

When a farm bill expires, both chambers of Congress independently draft a new one. The House of Representatives has passed its version. The Senate's is pending.

Ultimately, the versions must be melded into one passable package. The process can be contentious, and it's not uncommon for a farm bill to take years to renew. In the meantime, Congress extends the previous farm bill or passes interim legislation. The country's last farm bill, formally called the Agriculture Improvement Act of 2018, expired in 2023. Lawmakers have been extending the legislation. This latest extension expires on Sept. 30.

How the Senate will approach the issue of gestation crates and interstate commerce is an open question. Its version of an updated farm bill is expected to be released this month.