Forty-five cows suspected of having mad cow disease will be destroyed. The cows are from a farm in Japan's northern island of Hokkaido, where a cow died in January from the disease. It was Japan's 22nd case of mad cow disease.After the death of the cow, the Hokkaido government banned the farm from moving any of its more than 400 cows. The dead cow posed no danger to Japan's beef supply since it was not raised for food.The cows to be destroyed include 43 adults; and two calves which are the offspring of the cow that died last month. Japan guidelines on handling infected cattle requires that any cattle given the same feed and raised in the same pen for the first year of life with a cow that tests positive for mad cow disease must be destroyed as an infected animal. Calves born within two years of a mad cow disease outbreak among their herd are also considered as suspected infectious animals.The announcement came a month after Japan halted all imports of U.S. beef following the discovery of backbones in a shipment of American veal. The bones are said to be a mad cow disease risk and are banned under a deal that reopened the Japanese market to U.S. beef in December.The import halt was a harsh development for the U.S. beef business in Japan. In December 2003, Tokyo banned U.S. beef after the first American case of mad cow disease. The embargo was lifted in December 2005.