The RSPCA's investigating after undercover footage emerged showing pigs squealing as they're abused by workers at Fir Tree Farm in North Lincolnshire.
It's based in Elsham and is one of Britain's largest producers.
The charity Animal Equality has got hold of footage that shows staff kicking and prodding the animals, until they squeal with pain.
The Godfrey family, who own the farm, along with the company Elsham Linc LTD, have now dismissed the members of staff shown in the footage.
They said: "We are shocked by the actions of those involved as their abhorrent behaviour does not represent our business. We are a family run farm where the care and welfare of our pigs is paramount.
"We have been able to identify the four individuals in the film and following an immediate investigation their employment has been terminated".
Some employees were pictured swearing at the animals, as they joked about the abuse.
The RSPCA has started its investigation and the National Pig Association insists it does not tolerate or condone any violence or cruelty towards animals, adding it is clear that the actions of the individuals depicted in the footage are indefensible.