The United States has answered the Canadian Food Inspection Agency by requiring a test for avian influenza on all cows destined for Canada.
The testing becomes mandatory today.
The U.S. Department of Agriculture earlier announced testing would be required for all cattle crossing state borders.
Thirty-four herds in nine states have tested positive for the virus which has been responsible for the death of millions of chickens and turkeys in the United States and Canada. Infected poultry flocks are killed and quarantine zones restrict traffic around those farms.
There are no similar slaughter and quarantine-zone orders for cattle.
The U.S. has now begun to test ground beef from retail stores. Milk testing has turned up the virus in 20 per cent of samples.
