© Roberto Parada

On a rainy September morning, a pair of cattle ranchers browsed the refrigerated meat cases at a Walmart Inc. store in Mandan, N.D., snapping cellphone photos of an unwelcome invader among the shrink-wrapped ground beef: Beyond Meat Inc. patties, made from pea protein and coconut oil. After a separate check at a nearby local supermarket, the ranchers headed to the North Dakota Department of Health. They showed officials the photos and warned of food-safety risks from mixing plant burgers with the traditional beef kind.

Their message: Meatless burgers don’t belong on beef’s turf.

The impromptu inspection by the ranchers—one of whom was Kenny Graner, president of the U.S. Cattlemen’s Association—is just one front in a growing war against their plant-based rivals. Cattle ranchers and their allies are pushing regulators to scrutinize alternative meat-makers, recruiting food scientists to test plant-based products for potential health risks, and ramping up countercampaigns to highlight beef’s nutritional benefits while comparing their rivals to dog food.

They’ve even created a digital assistant, available on voice-activated Google and Amazon devices, that can answer consumers’ questions about beef and, when pressed, beef alternatives.

“The best alternative to beef,” it says, “is more beef.”

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Over the past two years, the beef industry has pushed legislation that restricts terms like “beef” and “meat” to the kind raised on the hoof, not products derived from plants or future ones developed using animal cells in labs. Various labeling laws are now are on the books in 12 states and were considered this year in 15 others, with a federal bill introduced in October.

For restaurants and grocery stores, growth is coming not from the real thing, but from a new generation of meatless products that combine proteins from soy or yellow peas with potato starch, beet juice and other ingredients to more closely mimic beef’s sizzle and juiciness. U.S. retail meat sales fell 0.4% in the past 12 months through October, while sales of alternative meat grew 8%, according to market-research firm Nielsen. In the 12 months before that, meat sales fell 0.8% while sales of alternatives rose 21%.

Plant-based alternatives amount to the equivalent of just 1% of the total volume of meat sold in the U.S., according to Nielsen. But some beef producers see an existential threat in the growth of meat-alternative makers like Beyond and Impossible Foods Inc.

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For a hint at the threat they face, they point to dairy farmers’ years-long losing battle against almond, soy and other imitation milks that have captured about 10% of sales, while consumption of traditional cows’ milk has declined.

“Anytime someone walks in the grocery store and makes a decision not to purchase our product and purchase another… we’ve lost a potential consumer,” said Jess Peterson, a cowboy-hat-sporting lobbyist for the U.S. Cattlemen’s Association who also raises cattle in Montana. “It’s a very small number, but it’s a number that can grow.”

Fast-food chains have raced to place meat alternatives on their menus. Burger King now sells an “Impossible Whopper,” White Castle has the “Impossible Slider” and Carl’s Jr., the “Beyond Famous Star.” Traditional meatpackers like Tyson Foods Inc., Hormel Foods Corp. and Smithfield Foods have developed their own meat mimics. In September, the products got their biggest endorsement yet when burger giant McDonald’s Corp. announced it would test a Beyond-based sandwich in 28 restaurants in southwestern Ontario. It’s called the “P.L.T.”, short for plant, lettuce, tomato, and it’s retailing for 6.49 Canadian dollars ($4.88) in a trial running through the end of the year.

Plant-based food makers promote their burgers as healthier for consumers, with a fraction of the environmental impact that comes from raising, transporting and slaughtering cattle. Part of Impossible’s stated mission is to end all livestock production, which the Redwood City, Calif.-based company calls “a prehistoric and destructive technology.”

“The whole point of our product is not to be successful as a new product, but to be successful at the expense of the incumbent industry,” said Pat Brown, Impossible’s chief executive and founder. “Obviously the incumbent industry is going to do whatever it can to throw obstacles in our way.”

Among those obstacles is a campaign to sow doubts about the benefits of meat alternatives. The Center for Consumer Freedom, a Washington-based nonprofit that is partly funded by meat producers and other companies, in 2018 began a campaign to counter consumers’ belief that meat alternatives are healthier than regular meat, critiquing what it says are the products’ heavily processed nature and reliance on fillers and additives that contribute to obesity.

The group, which has previously campaigned against animal-rights activists and soda taxes, started by penning op-eds in local and national newspapers and meat-industry websites, questioning meat alternatives’ processing and ingredients. Since July, it has bought ads in the New York Times, The Wall Street Journal and USA Today, blasting meat-alternative products with slogans such as “fake meat, real chemicals.” And a post on the CCF’s website in August highlighted a quiz that compared veggie-burger ingredients with those found in dog food.

The arguments over the ingredients in plant-based products are “silly,” said Jessica Almy, director of policy at the Good Food Institute, a Washington group promoting meat alternatives. Meat is also a processed product, as it contains all the food and medicine an animal took in before it was slaughtered, Ms. Almy said.

“Using scare tactics is a desperate attempt to stem the surging interest in these products,” she said.

Richard Berman, CCF’s executive director, said his group has also hired food-science labs to analyze potential health risks of meat alternatives, and plans to publicize the findings.

“I’m on offense,” Mr. Berman said. He declined to identify CCF’s funders.

In the spring of 2017, Kansas cattle producer Larry Kendig, a director of the U.S. Cattlemen’s Association, went to a series of regional farm shows to enlist ranchers’ support for a petition urging the U.S. Department of Agriculture to more tightly regulate plant-based food labels.

The FDA has jurisdiction over the labeling of plant-based products, and all foods except meat, poultry and egg products. That falls to the USDA, which has a dual role as a regulator of U.S. meat production and as a promoter of U.S. food products.

The FDA has permitted meat-free products to use meat terminology, like “bacon” and “beefy,” if their labels also bear identifiers like “vegan” or “plant-based.” Meat-alternative proponents say those terms give consumers an idea of their function, and that consumers buy the products because they contain no meat, rather than out of confusion.

The U.S. Cattlemen’s Association filed their petition in February 2018, asking the USDA to exclude meat-alternative products from the agency’s definition of “meat” and “beef.”

“We’re not about saying you can’t develop these products,” said the U.S. Cattlemen’s Mr. Graner. “We’ve been saying, don’t call it what it isn’t.”

About three months later, USDA investigators fanned out across Kroger Co., Safeway, Whole Foods Market, and other grocery stores in California, New Jersey, Ohio and Oklahoma. The investigators snapped photos of meat-free products made by Beyond, Late July Snacks LLC and Sweet Earth Foods, a subsidiary of Nestle SA, and made note of their locations.

At Berkeley Natural Grocery Co., in Berkeley, Calif., a store employee questioned the USDA inspectors’ motives. “I feel like you guys are going after these companies and that’s not right,” he said, according to the USDA’s record of the visit.

A USDA spokeswoman said the agency pursued the review because of concerns that “various stakeholders” raised over plant-based products allegedly misrepresenting themselves as meat and poultry. An FDA spokesman said the agency enforces truthful labeling for plant-based food products, and declined to comment on specific companies’ labels.

Nothing further came from those store visits. Ethan Brown, Beyond’s chief executive, said that the FDA hasn’t sought any changes to the company’s labeling.

Mr. Peterson, the beef lobbyist, nevertheless viewed it as a victory. “The goal of that petition was to do exactly what happened,” he said. “We wanted to elevate the issue to the federal agencies.”

In Washington, meat-alternative makers made early inroads in lobbying and advocacy. In 2016, startup Hampton Creek, now known as Just Inc., spent $110,000 to hire lobbyist Heather Podesta and her shop to make introductions to Washington officials as it was seeking to expand, according to the company and a disclosure form. Elizabeth Kucinich, the former policy director at the Center for Food Safety (and wife of former Democratic congressman Dennis Kucinich), was retained that year to represent the newly formed Plant Based Foods Association. And a lobbyist that group hired to focus on state fights has represented food and restaurant companies in Washington for years.

The cattlemen initially targeted state legislatures, joining with agriculture-friendly lawmakers and combining efforts to write laws to restrict how plant-based products use terminology like “meat,” “beef” and “sausage.”

Missouri became the first state to pass such a law in June 2018. Supporters there said the law would stop the plant-based producers from misrepresenting their products. Vegetarian-meat company Tofurky Co. joined with meat-alternative advocates to swiftly sue on First Amendment grounds, arguing in part that the law prevents them from labeling their products in ways that consumers understand.

“No one buys Tofurky ‘PLANT-BASED’ deli slices thinking they were carved from a slaughtered animal any more than people are buying almond milk thinking it was squeezed from a cow’s udder,” said the Good Food Institute, one of the plaintiffs in the case. The legal fight over the Missouri law is ongoing.

Other states including Mississippi, Louisiana, South Dakota and Wyoming have passed their own laws this year, and similar bills were debated in more than a dozen additional states including Iowa, Nebraska and Texas.

Mississippi, facing a legal challenge of its own, this fall opted to allow plant-based food makers to use some terms as long as they carry modifiers, such as “meat-free” hot dogs or “plant-based” bacon, a move that placated opponents.

Jaime Athos, chief executive of Tofurky, said he hasn’t yet modified the labels on the products his company sells because the legal challenges are ongoing, and he isn’t sure how he would comply given the variation in the state laws.

“These laws are written so ambiguously. It would be hard to change our labels because I’m not sure how we would,” Mr. Athos said. Tofurky is also a plaintiff in a similar legal fight in Arkansas.

As the legal challenges proliferate, cattle lobbyists like Aaron Propelka of the Kansas Livestock Association are crafting new state and federal bills that can withstand such lawsuits. One that he worked on with the National Cattlemen’s Beef Association, a Colorado-based beef group, was introduced in Congress by representatives from Kansas and New York in late October.

It would require plant-based products to be labeled as “imitation” meat products and hand the USDA greater authority over their labels. Mr. Propelka said he hosted the bill’s co-sponsor, Rep. Roger Marshall (R, Kan.), at his Topeka office as it was drawn up. Hearings on the bill haven’t yet been scheduled. The NCBA is working on a Senate version.

A separate battle is under way in grocery-store aisles and restaurant menus. Plant-based brands like Beyond, Impossible, Lightlife Foods Inc. and others are claiming more territory in the meat aisles of chains like Safeway and Kroger, while fast-food chains like Restaurant Brands International Inc.’s Burger King and Dunkin’ Brands Group Inc. air ad campaigns touting their new Impossible and Beyond-based sandwiches. (In its ad, Dunkin’ enlisted rapper Snoop Dogg to hand out breakfast sandwiches that have “that plant-based great taste.”)

In the middle are meat buyers like John Beretta, group vice president of meat and seafood for grocery chain Albertsons Cos. Mr. Beretta took a chance on adding one Beyond product in a single California store roughly three years ago after he was pitched by the company.

“I’m a meat guy. I thought it had some flavor, texture. We gave it a shot,” said Mr. Beretta, in the meat business for 38 years.

Now, meat alternatives command an entire section in Albertsons’ meat aisle, with Beyond sharing space with Lightlife and the store’s own plant-based products. About 90% of the 2,268 stores owned by Albertsons now have alternatives in the meat section, with the products sold from Maryland to Alaska.

“Our beef customers are enjoying it,” he said. “They are buying multiple packages of it at one time.”

Kroger, the largest conventional U.S. supermarket chain, is now testing alternatives in the meat aisles of 60 stores, after the Plant Based Foods Association pitched Kroger on a sales strategy this year. The test could expand to more stores depending on the results, a Kroger spokeswoman said.

Beef producers are expanding their own marketing efforts, relaunching in 2017 the famed “Beef. It’s What’s For Dinner” campaign, which officials said plays well with millennial consumers.

Alisa Harrison, the head of marketing and research for the NCBA, said the group hosts grocery-chain executives at the NCBA’s Denver culinary center, aiming to reinforce beef’s retail heft. “When people have beef in their basket, the overall ticket is higher,” Ms. Harrison said. “If you’re having steak, you’re more likely to have a bottle of wine.”

At the Annual Meat Conference last March in Dallas, NCBA officials introduced grocery-store officials and other attendees to Chuck Knows Beef, the digital assistant capable of answering questions about beef. Ms. Harrison said the NCBA has invested $1.5 million in beef-promoting technology initiatives like Chuck over the last three years.

Restaurants and retailers said they are trying to keep both sides happy. But mostly they want to sell more products, and increasingly plant-based meat alternatives are the products that generate buzz and customers.

“The Impossible Slider has built our sales,” said Jamie Richardson, vice president for corporate relations at White Castle System Inc., one of the first chains to roll out meatless patties nationally last year. “We aren’t walking away from that.”

Mr. Brown, Beyond Meat’s CEO, said he believes companies like his can peacefully coexist with meat producers, and potentially work together. The night before a major restaurant chain announced it would introduce Beyond’s yellow-pea protein-based burgers, Mr. Brown got on the phone, at the chain’s request, to talk with two cattle ranchers who raise beef for the chain. He declined to identify the chain.

Mr. Brown said he listened as the cattlemen rebutted criticisms of the meat industry. He suggested to them that grain and livestock producers could make more money by using some of their land to grow yellow peas and other crops used to make meat alternatives. He told them that the two camps didn’t need to be at odds.

That view faces a tough sell in beef country, where some ranchers said they can’t even bring themselves to try an Impossible Whopper at Burger King, or a Beyond Sausage Breakfast Sandwich at Dunkin’.

“Why would I?” asked NCBA President Jennifer Houston, whose family sells cattle in eastern Tennessee. “I’m a beef producer.”