Ranchers will have to slaughter about 10,000 cattle in the wake of the discovery of tuberculosis on one Alberta herd housed on three sites.
Dr. Harpeet Kochhar, chief veterinary officer with the Canadian Food Inspection Agency, said the animals are from some of the ranches that are under quarantine in southeastern Alberta.
"Roughly, if I was going to make an estimate of the number, it would be in the range of around 10,000 probably," he said Monday.
The agency said these animals are considered "high risk" for contracting or transmitting the infectious disease, even though only six cattle have tested positive for bovine TB since the first case was confirmed in September.
That cow was discovered at a slaughter plant in the United States.
The CFIA last week declared six properties among those considered as high risk for transmission.
Kochhar said the CFIA has added 12 more farms to the expanding list, bringing the total to 18.
So far, quarantine orders have been issued at more than 40 cattle operations in southeast Alberta and southwest Saskatchewan, affecting more than 22,000 animals.
He warned the number could increase again.
Ranchers and Tory politicians are complaining that the federal government's compensation for affected ranchers is too slow.