Experts believe that bovine spongiform encephalopathy (BSE) is spread through contaminated feed. A rendering plant that had been implicated in previous BSE investigations was linked to the two feed manufacturers identified as having supplied contaminated feed in this case.
Both of the feed manufacturers had procedures in place to maintain compliance with the 1997 ban on cattle feed containing rendered protein from cattle, sheep, goats and other ruminants. However, the CFIA said one of the facilities failed to "document a flush of equipment" that was used to make feed for non-ruminants -- using materials legal for other animals but banned from cattle feed -- before it was subsequently used to supply a commercial ration of cattle feed to the affected animal's farm.
"The procedural error associated with the 16 percent heifer grower ration makes that feed the most likely source of infection," the CFIA report said, but added that cross-contamination during transportation could not be ruled out. The infected cow was born five years after the 1997 ban was implemented, and is the youngest case in Canada so far.
While the seventh case prompted the participation of the U.S. government in the investigation and a halted a proposal to allow cattle older than 30 months to be imported from Canada, U.S. Department of Agriculture Secretary Mike Johanns said he did not expect a negative affect on trade between the two countries.
"We have said we will look at all of the events in Canada and try to factor that in," he said.
An eighth mad cow case, found in Alberta, was announced Wednesday by the CFIA.
In June, the agency announced it was striving to eliminate BSE within 10 years by banning cattle tissues that can transmit the disease from all pet and livestock feed.
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