US beef producer Excel Corp, a subsidiary of agribusiness Cargill, has said it has laid off up to 7% of its workforce at five US beef plants in response to lower beef demand caused by the discovery of a case of BSE, or mad cow disease, in Washington state in December.

"A number of countries have banned US beef, and there are some products we will not now be processing for export. That has led to the layoffs," Bill Rupp, Excel's executive vice president, was quoted by Reuters as saying.  

Excel said it would lay off between 100 and 150 people at each of its five US beef processing plants.

More than 20 countries, including top buyers Japan, Mexico and South Korea, banned imports of US beef after the discovery of the first US case of BSE in December.