Canadian cattle owners are holding their breath after a third Alberta-raised cow was diagnosed with bovine spongiform encephalopathy (BSE), or mad cow disease, on 11 January.

The US Department of Agriculture had earlier indicated its intention to lift a ban on Canadian beef cattle on 7 March, but this latest case has thrown that decision into doubt.

Canadian officials speculate that because the cow was born after a 1997 feed ban removing the use of ruminants in feed, it likely contracted the disease from contaminated surplus feed. They say no part of the animal has entered the human or animal feed system.