About 3,800 workers at the Swift Beef Co. plant in Greeley, Colorado, went on strike Monday, marking the first walkout at a U.S. beef slaughterhouse in four decades.

Strikers, many carrying signs in English and Spanish, protested outside the JBS USA-owned facility, citing alleged retaliation and unfair labor practices during contract negotiations.

Union officials said workers face dangerous conditions, insufficient pay, and high costs for personal protective equipment, while the company offered less than 2% annual raises, below inflation.

JBS maintained its contract offer was fair and blamed the union for halting negotiations, claiming many employees still reported to work, the AP has reported.

Workers emphasized their willingness to make sacrifices to secure better wages, healthcare, and respect for their role in the company’s profits.