FILE - Employees walk in front of the entrance to the JBS meat processing plant, July 23, 2021, in Greeley, Colo. (AP Photo/David Zalubowski, File)

GREELEY, Colo. — About 3,800 workers at one of the nation’s largest meatpacking plants went on strike Monday in Colorado in what union representatives said was the first walkout at a U.S. beef slaughterhouse in four decades.

Hundreds of strikers picketed in front of the Swift Beef Co. plant in Greeley, owned by JBS USA, as the sun rose Monday. They walked back in forth in the morning cold, bundled in blankets as some yelled “huelga!” — Spanish for “strike.” Others carried signs saying “please don’t patronize JBS,” written in both English and Spanish.

The strike follows accusations from union officials that the company retaliated against workers and committed other unfair labor practices amid contract negotiations. A previous contract expired Sunday night.

“They don’t really value their workers and we’re the ones that help them get all their profit,” said Leticia Avalos, a 34-year-old union steward and Greeley native who has been working at the plant since 2020.

Avalos said she depends on the job to support her family including a 6-month-old baby, but she’s willing to make sacrifices to get the company to listen.

“It’s the number one place where all of Greeley works,” she said. “It’s a huge impact in the community for us to be striking. I know a lot of us are worried, and hope that nothing goes even more south.”

Smoke was rising from parts of the plant but it was unclear if it was still operating.

A spokesperson at JBS USA said late Sunday that the company stands by its contract offer, describing it as fair.

“Despite our continued efforts to reach a fair and responsible agreement, Local 7 chose to end negotiations and cancel the contract we had in place,” spokesperson Nikki Richardson wrote in an email.

The union said in a news release that its workers “perform some of the most difficult and dangerous jobs in the country.” It said JBS in many cases has charged workers $1,100 or more to offset the company’s expenses for personal protective equipment needed to ensure worker safety.

“They deserve wage increases that keep pace with inflation, ensure they receive healthcare commensurate with the toll this work takes on their bodies, and that allow them to live with dignity and respect.”

The strike comes at a 75-year low for the U.S. cattle population, with a Jan. 1 inventory of 86.2 million animals — down 1% from the prior year.

Beef prices have soared to record levels in part after drought and years of low prices led to the smallest U.S. herd size in decades. President Donald Trump’s tariffs on Brazil, a major beef exporter, have also curbed imports.

The price for 100% ground chuck beef more than doubled over the past two decades from $2.55 to $6.07 per pound, according to the Bureau of Labor Statistics. The increase has added to economic anxiety in the U.S., while the administration Trump has turned to a trade deal with Argentina in efforts to lower prices for food, including beef.

The strike also follows the January closure of a meatpacking plant in Lexington, Nebraska, which was expected to ripple through the local economy and community. Tyson Foods cited the smaller herd and millions of dollars in expected losses this year.

At the Greeley plant, the company tried to intimidate workers to quit the union in one-on-one meetings, union general counsel Matt Shechter said. A JBA USA statement issued before the strike said the company fully complies with federal and state labor and employment laws.

Kim Cordova, president of the United Food and Commercial Union Local 7, said 99% of workers voted to authorize the strike. No formal negotiations took place over the weekend after the company refused a union request to negotiate on Saturday, Shechter said.

Company spokesperson Richardson said any employee who didn’t want to strike would have work and be paid. The company said it would operate two shifts at the plant Monday and would temporarily move production as needed to other JBS facilities.

It’s the first strike at a U.S. slaughterhouse since workers walked out at a Hormel plant in Minnesota in 1985, Cordova said. That strike lasted more than a year and included violent confrontations between police and protesters, according to the Minnesota Historical Society.

Claire Poundstone, an attorney representing the union workers, said she expected workers to participate in the strike line through the evening.

“We’ll be here all day,” she said.