In 1999, the cattle population was about 2,380,000. Other livestock included 1,835,000 goats; 250,000 sheep; 33,000 horses; 235,000 donkeys; and 4,000,000 poultry. Cattle are valued for wealth and prestige and are used in the payment of bride price, but there is little of the cultural prohibition against selling cattle found in some other parts of Africa. Herds are grazed in the open veld where water and grass are available; the borehole-drilling program is extending the available grazing land. A gradual upgrading of stock quality has been achieved through selective breeding, culling, and controlled grazing. A system of disease-control fences has been installed. A vaccine institute was opened in 1981 to deal with the threat of foot-and-mouth disease. In the mid-1980s, the Botswana Meat Commission's plant at Lobatse was the largest export abattoir in Africa. In 1999, meat production totaled 63,000 tons, with beef accounting for 41,000 tons. Much of Botswana's annual beef production is exported to South Africa and Western Europe. Beef and beef products are Botswana's second largest export earner (after minerals); about 215,000 cattle were slaughtered in 1999. In 2001, exports of live animals earned $1.6 million.