The business practices of Smithfield are a far cry from its origins, lovingly recounted in sepia-tinted prose on its corporate website. "The Luter family of Smithfield, Virginia, has been curing and selling hams since the turn of the century," it says.

Critics say that - even on top of any questions about the humane treatment of the pigs - the sheer quantities of manure that have to be disposed of when thousands, or tens of thousands, of animals are housed together make it impossible to run this business in a safe way.

The manure is collected in a lake underneath the pig pens and then washed into giant pools or lagoons. It is eventually sprayed on nearby fields, but the lagoons have a habit of leaking or flooding. In 1997 Smithfield was fined US$12.6 million for violating the federal Clean Water Act.

The other risk, scientists say, of concentrating so many pigs together is the risk of diseases spreading fast, a problem that farmers overcome by pumping the livestock full of vaccines and other drugs. In 2007 an outbreak of swine flu at its farms in Romania cost the company US$13 million.

Smithfield says it is always investing in research to improve farming methods and operates its facilities to the highest standards. Its public relations message is complicated, however, by the uncompromising stance of chairman Joseph Luter III.

Animal rights activists "want to impose a vegetarian society", the 67-year-old once said, and vegetarians were "neurotic".

- INDEPENDENT

By Stephen Foley