It was still dark when Jay hit the highway. At 6 o’clock that morning, he would be starting his first shift at Quality Pork Processors, part of the Hormel Foods complex in Austin, Minn., almost an hour’s drive down Interstate 90 from his rented apartment in Rochester. He’d applied for the job on the meatpacking line barely a week earlier and was still mentally preparing for it. “When you’re in the car,” he told me recently, “you have to go over everything again.” He had to remember his story: where he was from, why he was there. He had to remind himself what he could and couldn’t say. He was going to be meeting a lot of new people that day, and it would be essential not to arouse suspicions.

Just before the exit off the Interstate, Jay passed an illuminated billboard for Austin’s Spam Museum: “FIND SALIVATION.” He steered down the winding road along the plant perimeter, past the high wall guarding the loading docks, until he came to the Q.P.P. employee entrance on Hormel Century Parkway. The factory was already enveloped in steam; overnight cleaning crews had hosed down the stainless-steel cutting line, and now the compound’s six-story hydrostatic Spam cooker was warming for the day shift. The steam billowed and swirled in the lights of the plant. Jay shuffled into the line of workers making their way through the employee turnstile. He swiped in and headed through the glass doors to where the day’s freshly laundered uniforms were being handed out, color-coded according to department.

“What station?” the person at the window asked.

“Gam table,” Jay said. His job would be slicing open the rear legs of hog carcasses, loosening the tendons of the trotters and inserting a gambrel. “It looks like a clothes hanger, but with hook tips that point up,” he told me. The gambrel attaches to a trolley that carries the carcass on a chain conveyor system as it is broken down into “primal cuts,” before being sent to the Hormel Foods side of the plant for final processing and packaging.

Jay knew that the job would be physically grueling. To keep up with the speed of the line, a carcass had to be cut and hung in about six seconds. But more than that, it was going to be psychologically — even morally — taxing for him. Jay had been a vegetarian since he was in college. He couldn’t say why he quit eating meat, really, only that he always loved animals and that his vegetarian younger sister convinced him.

But in recent years, Jay’s commitment had grown. He became a vegan. When he was online, he found himself drifting toward websites of animal rights groups, pulling up footage of abuse shot by undercover investigators. One day it occurred to him that he should try to find such work. On a job site, he found an opening at Compassion Over Killing, or C.O.K., an advocacy group intent on ending cruelty to animals in agriculture and promoting vegetarianism. And just like that, he entered the shadowy world of undercover video activism, where no one around you knows whom you really work for and few people, not even your family and friends, know where you are or what you’re doing for months at a stretch. (To protect his identity, Jay uses only his middle name when speaking to reporters.)

Now, as Jay dressed in the locker room, put on a hard hat and picked up gloves in the equipment room, he could feel a weight descend on him. Once you’re inside, he said, you realize how alone you are. “You’re going to be out there pretty much by yourself,” he told me. “You’re going to be working these really long hours and seeing animal abuse on a day-to-day basis.”

His manager at C.O.K. had warned him that it would be months before he could transfer to the kill side of the plant, where live animals are handled, and weeks more before he would have enough video to complete the investigation. Every day for five or maybe six months, Jay would have to walk past posters reminding employees that all cameras were strictly prohibited inside the plant and to immediately report any suspicious individual, even if that person was a co-worker. The isolation and paranoia can be consuming, he said, coloring every sidelong glance, every passing conversation. “It’s definitely something that’s always there in the back of your mind,” Jay told me. “When you’re talking to people, you really have to just focus on who you’re supposed to be.”

When picking among shrink-wrapped packages in the meat aisle of your local grocery, it’s remarkable how little information you’re provided about the steak, pork chop or chicken breast inside. The label tells you the particular cut, its weight and the price per pound, but store brands almost never give even basic information about how that animal was raised. In December, Congress repealed its country-of-origin labeling requirements for beef and pork, so now meatpackers don’t identify where the animal came from. Beef commands a premium if it is labeled “grass-fed” or “naturally raised,” but the Department of Agriculture withdrew oversight of those terms in January and no longer verifies such claims. Even in cases where the U.S.D.A. does certify labels, the rules can be slippery. The term “humanely raised,” for example, has no standard definition, and the U.S.D.A. does not conduct site visits to confirm enforcement for those approved to use the label.

Amid such dwindling transparency and oversight, animal rights activists, once regarded as the radical fringe, have taken on a somewhat unlikely role as consumer watchdogs. Trading provocations (splattering fur-wearing models with fake blood) for middle-ground strategies (“Meatless Monday”), they are drawing the attention of not only shoppers concerned about humane animal handling but also food-safety advocates and environmental groups who worry about the ecological impact of large-scale meat production. The principal tool of this public-relations effort has been daring hidden-camera footage, released in slickly edited videos that aim to shock consumers about what really happens on the production line.

Undercover investigations of the American meat industry go back at least as far as the early 20th century, when Upton Sinclair lived in the Packingtown section of Chicago, gathering material for his classic muckraking novel, “The Jungle.” During his two months there, Sinclair made several visits to the Armour slaughterhouse, which he rendered in vivid detail. Sinclair had hoped to arouse public outcry over the treatment of workers; instead, readers were horrified by the unsanitary conditions in which their meat was slaughtered and butchered. J.Ogden Armour publicly denounced the book, declaring, “Not one atom of any condemned animal or carcass finds its way, directly or indirectly, from any source, into any food product or food ingredient.” Sinclair responded with a letter addressed to President Theodore Roosevelt: “I saw with my own eyes hams, which had spoiled in pickle, being pumped full of chemicals to destroy the odor. ... I saw hogs which had died of cholera in shipment, being loaded into box cars to be taken to a place called Globe, in Indiana, to be rendered into lard.”

Roosevelt demanded that Congress pass immediate reforms. The Federal Meat Inspection Act of 1906 mandated adherence to new sanitary standards and the presence of federal inspectors to enforce these rules. Any product that failed to meet the new standard was to be condemned.

The strength of these reforms, combined with consumer eagerness for cheap meat during the hard times of the Great Depression and food rationing of World War II, ushered in a golden age for the industry. Meat sales soared, workers’ wages climbed and the industry engaged consumers in a new spirit of openness and transparency. As late as 1965, a business like George A. Hormel & Company was advertising public tours of its plants. The company even produced a half-hour educational film called “This Is ... Hormel,” showing four farm boys and their father on a tour of the Austin slaughterhouse. “From balconies,” the narrator says, “you can look across entire rooms of assembly — or rather disassembly — activity.”

All that started to change in the 1970s, as the meatpacking industry mechanized and moved away from skilled labor. Confined animal-feeding operations, commonly known as “factory farms,” were born and sustained by the intensified production of crops like corn and soybeans for feed. By the Reagan era, Americans had fallen in love with microwaveable food, frozen food and especially fast food. The number of McDonald’s franchises, as just one metric, had grown from fewer than 150 stores in 1959 to more than 11,000 in 1990.

In this new climate, the industry began to manage its image as aggressively as it had begun to manage its animals. Large producers successfully lobbied Congress to create a “checkoff” program, which imbued private industry with the power, via the U.S.D.A., to collect a percentage of all beef and pork sales to be used for the general promotion of eating meat. But the bill also included language from meat producers, specifying that “despite the fact that many of our members may produce a commodity that is the subject of governmental price supports, we are opposed to increased government intervention or regulation.” Thus began an era in which U.S.D.A. officials began to view themselves as partnering with industry, rather than monitoring it.

Soon groups like People for the Ethical Treatment of Animals, which had focused almost exclusively on abuses of laboratory animals and anti-fur campaigns, decided to begin conducting their own sorts of inspections. C.O.K. scored an important victory when its investigators videotaped chickens crowded, sometimes eight per crate, into rows of wire cages stacked at a barn owned by I.S.E. America, which sold eggs with the industry-created Animal Care Certified seal. C.O.K. filed a Better Business Bureau challenge to that self-certification and eventually won. I.S.E. dropped the label.

The North American Meat Institute, the lobbying group representing most of the country’s largest meat companies, complains that consumers are being misled by animal rights activists, who, they say, are not simply encouraging consumers to reduce meat consumption but are also opposing consumers’ right to eat meat, cheese and dairy, all as part of what one headline on the institute’s website called “the liberal vegan agenda.” Mike Wolf, the manager of C.O.K.’s undercover investigations, doesn’t deny that animal rights organizations are trying to persuade consumers “to move toward a plant-based diet,” but he insists that meatpackers are the ones who have created the necessity for undercover investigations by blocking consumers from seeing how their food is made. With the government working hand in hand with business, the only remaining window into the food system is the lens of an activist’s camera.

Exposing the industry’s standard practices, Wolf argues, generates a demand for change from legislators and, perhaps more significant, from major restaurant chains. In 2012, for instance, after the Humane Society of the United States released undercover footage of pregnant sows immobilized for months in narrow “gestation crates” at a Smithfield Foods subsidiary, McDonald’s announced that its breakfast sausage would no longer be made from pork bred in gestation crates — and Smithfield, along with other major pork producers, raced to announce that it was phasing the devices out. The industry opposes undercover investigations, Wolf says, precisely because they work.

When Jay arrived in Minnesota, he wasn’t specifically targeting Quality Pork Processors. He applied for jobs at several plants, and Q.P.P., which sends all the fresh meat it processes to the Hormel Food Corporation in another part of the complex in Austin, was simply the first to call him back. But once he got the offer, Mike Wolf let him know that this wasn’t just any meatpacking plant. It was one of only five pork packinghouses nationwide where the U.S.D.A. was experimenting with a controversial new form of oversight. Introduced in 1999, the program — called Hazard Analysis and Critical Control Points-Based Inspection Models Project, or HIMP — replaced traditional manual inspection with a “risk based” approach. Meat-industry managers would hire their own quality-assurance auditors to identify and remove obviously sick or defective animals from the line before they reached government inspection stations, and employees from the U.S.D.A.’s Food Safety and Inspection Service would instead focus their efforts on more sophisticated microbiological testing in places where contamination was most likely to occur.

The U.S.D.A. called HIMP a “hog-slaughter modernization” program that allows the F.S.I.S. to perform more inspections, but activists contend that the program is less about modernization than it is about reducing government oversight in order to increase production speed and therefore profits.

In May 2013, two years before Jay went undercover in Austin, the inspector general’s office for the U.S.D.A. issued a stinging critique of HIMP. Three HIMP plants had made it into the top 10 for food-safety violations out of 616 pork-processing plants nationwide. Such numbers, it reported, represented “a systemic failure” that should have resulted in more aggressive enforcement action or even a halt in production. In 2014, though, the U.S.D.A. not only approved the continuation of the HIMP pilot project but also called for a review to determine if the program “could be applied to additional establishments.” In January 2015, the Government Accountability Project, a nonprofit whistle-blower-protection organization, released affidavits from four federal inspectors from HIMP facilities attesting to food-safety violations. A U.S.D.A. spokesman dismissed them as being “part of a well-funded and organized public-relations campaign.”

In Jay’s time at the gam table, he shot video of numerous hogs with obvious fecal contamination being processed for food. In one sequence, Jay cuts into the hind legs of four different carcasses, and pus-filled abscesses under the skin pour forth a brownish-green ooze or spray clear liquid across the workstation. Though the footage Jay collected at the gam table was disgusting, the U.S.D.A. says procedures were in place to ensure that the infected tissue was removed farther down the line.

Jay was eager to move to the live-animal area, where he could see how hogs were treated in a part of the plant where U.S.D.A. inspectors had been virtually replaced by Q.P.P.—hired quality-assurance auditors. Once Jay had enough seniority, he bid on a transfer to the station known as “stick, stun and shackle,” where pigs are shocked to death, drained of their blood and shackled to the conveyance chain.

Almost immediately after Jay was transferred, he saw — and was able to record — multiple instances of behavior that seemed far out of compliance with U.S.D.A. rules for the humane treatment of livestock. (Q.P.P. maintains that he never reported any of that behavior to supervisors, as was his duty.) He filmed a hog being hit in the face with plastic rattle paddles and electrically prodded on the head. He filmed another hog being repeatedly beaten then rolled and pushed by its hindquarters. He filmed hogs having their throats slit while still alive and — in one particularly harrowing sequence — appeared to capture a hog struggling to right itself in its shackle as it is carried toward processing. A spokesman for Q.P.P. said all the hogs “had been properly rendered insensible,” but the video itself seems to contradict that claim. At one point, a worker shouts over the din of machinery and squealing pigs: “Too many sensibles. If U.S.D.A. is around, they could shut us down.” Because of HIMP reductions, however, the U.S.D.A. wasn’t around.

In October 2015, when Compassion Over Killing put out a news release and a five-minute video made from Jay’s footage, the story was national news. “The actions depicted in the video under review are appalling and completely unacceptable,” said Adam Tarr, a U.S.D.A. spokesman. Q.P.P. said that, before the release of the video, it reprimanded the worker — Jay — who cut into the pus-filled abscesses for departing from company procedure and would now reprimand another employee for aggressive behavior and would introduce “corrective measures” to improve animal handling.

In January 2016, Representatives Rosa DeLauro of Connecticut and Louise Slaughter of New York led a bipartisan group of 60 members of Congress urging the U.S.D.A. to delay proceeding further with HIMP until the U.S.D.A. could provide evidence that it is an effective program. The very next day, the U.S.D.A.’s Office of Investigation, Enforcement and Audit closed its inquiry into the plant. “The actions depicted in the video occurred at times when U.S.D.A. inspection personnel were not performing verifications,” a letter from the U.S.D.A. to C.O.K., in response to the beatings, reads. “Had these actions been observed by F.S.I.S. inspectors, they would have resulted in immediate regulatory action against the plant.” But because these actions were not directly observed by U.S.D.A. inspectors, the department could only demand that Q.P.P. document how it would improve animal handling.

Mike Wolf was exasperated: “How can you say, ‘If we were there to see it, we would have done something,’ on one hand, and on the other hand say, ‘O.K., well, we’re going to pass this [rule] now so that we’re not going to be able to see anything’?”

As video activists push harder, the industry is pushing back, against not just activists but also journalists and whistle-blowers, with laws to prosecute a new kind of crime: “animal-facility interference.”

In 2011, State Representative Annette Sweeney of Iowa introduced H.F.431, a bill that sought to make it illegal to produce, possess or distribute any record of “a visual or audio experience occurring at [an] animal facility.” Sweeney, a former executive director of the Iowa Angus Association, wrote the bill at her kitchen table with input from lawyers for the Iowa Poultry Association. The law that eventually passed, H.B. 589, makes it a crime only to give a false name on a job application, but the intention was clear.

Since then, four more states have passed similar measures, known collectively as “ag gag,” with each law more ambitious than the last. Last year, for example, legislators in North Carolina, still the largest hog producer in the United States, passed an anti-whistle-blower law that gives businesses the authority to sue any person, including employees, who have accessed nonpublic areas of the workplace in order to document company lawbreaking. Wyoming passed a law that makes it a crime to “preserve information in any form” about any “private land” if you intend to share the data with the federal government — potentially shielding cattle ranchers from being cited by the Environmental Protection Agency for polluting state waterways.

Wolf told me that the industry response over the last decade has made him think hard about the limits of undercover videos. While the camera may expose inhumane or unappetizing actions at a place like Quality Pork Processors, it doesn’t capture the corporate higher-up who demanded increased production, the industrial engineer who came up with a work flow to make it happen, the union boss who approved the speedup or the floor supervisor who berates workers who fail to keep pace. The hidden cameras carried by undercover investigators provide our only view onto the meatpacking industry, but they are a pinhole, not a panorama.

As such, the view is imperfect — and, the meat industry says, distorted. But its best defense from the animal rights activists may be simply to reinstate the power of the government-led transparency that we had in the mid-20th century. If companies like Hormel feel that they have been misrepresented, they might do better seeking more transparency, not less.

Ted Genoways is a writer whose book “This Blessed Earth: A Year in the Life of an American Farm” will be published next year by W.W. Norton.