Livestock continues to be the largest sector of the farming industry. The United Kingdom raises some of the world's finest pedigreed livestock and is the leading exporter of pedigreed breeding animals. Most of the internationally famous breeds of cattle, sheep, hogs, and farm horses originated in the United Kingdom. In England and Wales, fattening of animals for food is the predominant activity in the southeast, the east, and the Midlands, while stock rearing is widespread in northern England and in Wales. In Scotland, dairying predominates in the southwest, cropping and fattening in the east, and sheep raising in the hilly regions. Northern Ireland's livestock industry provides 90% of its agricultural income.
In 2001, there were about 10,600,000 head of cattle (including two million dairy cows), 36,697,000 sheep and goats, and 5,845,000 hogs. There are also an estimated 167 million chickens. Output of livestock products for 2001 included 645,000 tons of beef and veal, 258,000 tons of mutton and lamb, 777,000 tons of pork, 1,565,000 tons of poultry, 14,709,000 tons of milk, 126,000 tons of butter, and 385,000 tons of cheese.
The most highly reputed beef breeds are Hereford and Aberdeen Angus; distinguished dairy breeds are Guernsey, Jersey, and Ayrshire. To ensure sound breeding, there is compulsory licensing of bulls. On 20 March 1996 the British government reported concern over a possible link between bovine spongiform encephalopathy (BSE, or the so-called "Mad Cow" disease) in cattle and a new variant of Creutzfeldt-Jakob disease in humans. BSE was first identified in the United Kingdom in 1986. Transmission of BSE to cattle occurs from contaminated meat and bone meal in concentrate feed, with sheep or cattle as the original source. The United Kingdom is the only country with a high incidence of the disease, and the epidemic was mainly due to recycling affected bovine material back to cattle before a ban on ruminant feed began in July 1988. As a result, consumption of beef dropped and many countries banned imports of British cattle and beef.