Pilgrim's UK, one of Britain's biggest farming and food businesses, is planning to close two sites as the firm recorded an operating loss of £16m in 2021.
The company's Bury St Edmunds and Coalville sites could be shut down, and its site at Ashton may have production lowered to four days.
Overall, closure of the Suffolk and Leicestershire processing sites could lead to the loss of hundreds of jobs.
The company posted an operating loss of £16m in 2021 in its latest accounts, following an extremely challenging time for the UK pig sector.
In a statement, the company said “some sites are significantly under-utilised in terms of operational capability and capacity”.
Rachel Baldwin, vice president of HR for Pilgrim’s UK said: “The decision to propose the closure of our sites and put a number of roles at risk at Ashton has not been taken lightly.
"But [it] is unfortunately essential to help our business recover and secure a sustainable future for all of our team members across the UK.”
Existing operations at the two closed plants would transfer to plants at Corsham, Kings Lynn, Linton and Andover, Pilgrim's UK said.