Chicago, Feb 10: A ban on US chicken by big overseas buyers due to a case of bird flu in Delaware sent shares of major US poultry companies lower on Monday in the latest shock to the livestock industry over food safety. Shares of Tyson Foods Inc., Pilgrim's Pride Corp. and Sanderson Farms fell after Japan and South Korea banned US chicken. Russia, the top buyer of US chicken, banned only chicken from Delaware. US livestock and grain markets were also jolted by the shock of yet another meat safety threat after December's first US case of mad cow disease and a virulent but different form of bird flu now decimating poultry flocks in Asia. At the Chicago Mercantile Exchange, live cattle prices fell as much as the 1.50-cent-a-pound daily limit early on concern that US poultry blocked from export markets would enter domestic markets and pressure all meat prices. But cattle prices later recovered to end mostly higher. Some 12,000 chickens were destroyed at a Delaware farm on Saturday after two birds tested positive for the H7 avian influenza virus, which is different from the H5 strain that has killed more than a dozen people and decimated poultry stocks in 10 Asian countries. Fast-food chain McDonald's Corp. said it does not use Delaware poultry, and Yum Brands Inc., owner of the KFC chicken restaurants, said it has no relationship with the Delaware farm. Bureau Report