Exclusive-Senate Democrats question USDA about data errors, staff losses

By Karl Plume CHICAGO, Aug 20 (Reuters) - U.S. Senate Democrats asked the Department of Agriculture late on Wednesday to explain what caused the agency to vastly overstate beef export sales last month and what role department staff losses played in the mistake. Six senators, led by Amy Klobuchar, a Democrat from Minnesota and ranking member of the Senate Committee on Agriculture, Nutrition and…