A herd of nearly 70 cows is being slaughtered after a farmer illegally gave them rabbit and guinea pig food containing pulverised cattle bones.
The herd at Mr Podger's farm was removed by government vets
Percy Podger, from the farm in Surrey claims he had no idea the food contained banned bovine material.
It is illegal to feed the material to cows destined for the food chain because of the risk of vCJD infection, the human form of mad cow disease.
Government vets took the cows from Pond Farm, Godalming, on Tuesday.
Mr Podger's farm has been investigated by officials from the State Veterinary Service on a number of occasions and has twice been prosecuted for failing to observe rules about record-keeping and tagging of cattle herds.
It is also operating under movement restrictions following prosecutions over animal legislation breaches.
Mr Podger said Surrey Trading Standards Officers and officials from the Department for Environment, Food and Rural Affairs (Defra) removed seven bags of pet food from the farm.
"I only used part of a bag in the mix for the cattle," he said.
"It was sold to me as commercial rabbit food - and rabbits should not be fed anything with bonemeal or other traces of meat in it."
Defra said the government's Veterinary Laboratories Agency (VLA) carried out tests on the food.
"The test results showed that the pet food (intended for rabbits and guinea pigs) that Mr Podger was feeding his cows contained some bovine material and was unsuitable for cattle feed," Defra said.
A spokeswoman said Mr Podger told vets he had no idea the rabbit food contained bonemeal and investigators found the containers did not mention it as an ingredient.
A Trading Standards inquiry is currently under way into the origins and type of pet food fed to the cows as well as how it was sold to Mr Podger.
Steve Reddy, Assistant County Trading Standards Officer for Surrey, said material banned from the human food chain was not necessarily banned from pet food.