The closures are limiting the amount of meat the United States can produce during the COVID-19 pandemic and providing additional stress for farmers who are already losing markets for their pigs.

Lockdowns that aim to stop the spread of the coronavirus have also prevented farmers around the globe from delivering food products to consumers. Millions of labourers cannot get to fields for harvesting and planting, and there are too few truckers to keep goods moving.

Tyson Foods said it will indefinitely suspend operations at its largest pork plant in Waterloo, Iowa, after operating at reduced capacity.

Plant employees tested positive for the virus, and others stayed home out of fear of becoming infected. The facility slaughters about 19,500 hogs a day, or about 5 percent of total US pork production, according to industry data.

Tyson also plans to close a pork processing facility in Logansport, Indiana, while its more than 2,200 workers at the plant undergo testing for COVID-19.

"Consumers will see an impact at the grocery store as production slows," Tyson Fresh Meats Group President Steve Stouffer said.

"It means the loss of a vital market outlet for farmers and further contributes to the disruption of the nation's pork supply."

When the Logansport facility closes, slaughterhouses that account for 19 percent of pork production in the United States will be shut.

Brazilian-owned JBS USA and WH Group's Smithfield Foods have also each indefinitely closed massive pork plants in Minnesota and South Dakota, respectively.

Reduced meat output comes as demand has increased at grocery stores, while restaurant dining rooms are closed due to the virus.

Tyson said 2,800 workers at the Iowa plant would be compensated during the closure and invited to the facility later this week for coronavirus testing. The outcome of the tests and other factors will determine when the facility will reopen, according to the company.

Other US meat and poultry plants are operating at reduced capacity. Tyson is running a pork plant in Columbus Junction, Iowa, with limited operations after idling it for two weeks.

Iowa farmer Randy Francis delivers 300 pigs to 500 pigs a week to the Waterloo plant for slaughter that are backing up in his barns. He hopes to truck the animals to other plants, but they are already overloaded with other hogs displaced by the shutdowns.

The pigs will put on more weight than normal due to the delays, Francis said. That could make their meat fattier or tougher to chew when they are eventually slaughtered, he said.

"It's definitely scary times," Francis said.