The U.S. Department of Agriculture proposed a new, mandatory system Tuesday for tracking cattle, poultry and other farm animals to pinpoint the origin of diseases that can spread through herds and halt exports.

Ranchers and farmers under the rules would be required to affix a unique identification number to animals transferred between states or tribal areas. The tracking system would allow federal officials to more quickly find the source of an outbreak and isolate the diseased animals, reducing the economic and public-health impacts, the USDA said.

U.S. Agriculture Secretary Tom Vilsack in a conference call said the tracking system would help reassure foreign meat buyers, some of whom have been critical of the U.S. system for disease control. The lack of a more rigorous system became an issue in December 2003 when the first U.S. case of mad-cow disease was discovered