Rise of mega farms: how the US model of intensive farming is invading the world

Demand for cheaper food and lower production costs is turning green fields into industrial sheds to process vast amounts of meat and poultry

• UK has nearly 800 livestock mega farms, investigation reveals

Since the days of the wild west frontier, the popular image of American farming has been of cowboys rounding up steers on wide open ranches, to whoops, whips and hollers. Today, the cowboys on their ranches under wide open skies have been replaced by vast sheds, hulking over the plains, housing tens of thousands of animals each, with the noises and smells spreading far beyond their fences.

The US has led the world in large-scale farming, pioneering the use of intensive livestock rearing in hog farms, cattle sheds and sheep pens. There are now more than 50,000 facilities in the US classified as concentrated animal feeding operations (CAFOs), with another quarter of a million industrial-scale facilities below that threshold.