Sheep are the main livestock product, with Karakyl sheep (noted for their black wool) raised in the Bukhara region. The livestock population in 2001 included 8.1 million sheep, 5.3 million head of cattle, 830,000 goats, 89,000 pigs, 165,000 donkeys, 150,000 horses, 28,000 camels, and about 14 million chickens. Meat production that year totaled 512,000 tons, of which 77% was beef, 17% was mutton, 3% was pork, and 3% was poultry. Wool (greasy) production in 2001 was estimated at 15,900 tons. Mulberry trees have been grown for silkworm breeding since the 4th century; some 1,200 tons of silk were produced in 2001.