Britain’s National Pig Association has warned that recycling human food by feeding it to pigs must only take place under strictly controlled conditions, in an effort to prevent national outbreaks of economically damaging diseases such as foot-and-mouth and classical swine fever, following a recent attempt by an environmental campaigning charity to highlight the benefits of pig farming by giving left-over food to pigs in London's Trafalgar Square.

Friends of the Earth, an environmental charity, attempted to feed pigs leftovers as a publicity stunt to highlight the economic benefits to pig farming. The National Pig Association general manager, Dr. Zoe Davies, however, says the group "really shouldn't have done that."

“We find it difficult enough trying to explain to people why it is wrong to feed waste food to pigs without this kind of high profile stunt, however well meant,” Davies said.

A UK ban prevents feeding waste food from catering establishments, including home kitchens and restaurants, to animals, which has been in effect since Britain's 2001 foot-and-mouth disease outbreak. The law also covers food waste from other premises, including food factories and distribution warehouses that contain or come in contact with animal by-products such as raw eggs, meat and fish products.

“We understand Friends of the Earth acted with the best of intentions and was at pains to comply with all the legal issues, but we remain concerned that promoting the image of pigs eating waste food is unhelpful,” said Davies. “The pig industry does use a tremendous amount of by-product from food manufacturing, but only as part of a tightly regulated process.”