Truckloads of Canadian beef have crossed the border into the US for the first time since May when a single case of mad cow disease was discovered in Alberta.

Following the discovery of a case of bovine spongiform encephalopathy, or mad cow disease, in a cow in Canada on 20 May, Canadian beef shipments have been banned to more than 30 countries, including the US.

The US Department of Agriculture is now allowing imports of boneless meat from Canadian cattle under 30 months old, reported AP Online.

Imports of live cattle from Canada are still banned, but the USDA is reportedly preparing to accept live cattle imports from Canada, a move which may cause trade problems between the US and Japan.

Japan is currently only allowing imports of US beef that carries an assurance that it is not derived from Canadian cattle.

Chandler Keys, a vice president of the US National Cattlemen's Beef Association, said he expects the USDA to be ready to open the border to Canadian live cattle imports in around six months time, but negotiations with Japan will have to begin sooner to ensure trade is not disrupted, reported Dow Jones Commodities Service.

A USDA official said it was easy at the moment to ensure that all the beef from US slaughterhouses is of US origin, because no Canadian cattle are currently being slaughtered in the US. That would change, however, when the US begins accepting imports of Canadian live cattle.