Vegan activists have been “uttering soft words” to animals being driven to an abattoir to be slaughtered.
The campaigners “bear witness” with the agreement of the slaughterhouse’s owners in Melton Mowbray, Leicestershire.
The National Pig Association said it has seen an increase in attacks against farmers by some hardline activists.
But Dina Aherne, who leads Leicestershire Animal Save, said her group does not condone such behaviour.
You can see this BBC Inside Out story in full on BBC One in the East Midlands on Monday at 19:30 or via iPlayer after broadcast.