OTTAWA – The Canadian Food Inspection Agency is blaming pre-feed ban ruminant meat or bone meal exposure as the source of bovine spongiform encephalopathy, or mad cow disease.
The investigation included trace-back, trace-forward and feed investigations that spanned four provinces and included some 2,700 animals.
Feed investigation. The agency’s feed investigation was designed to identify all feeds that the index case consumed and determine if any contained ruminant meat and bone meal.
Feeding of ruminant meat and bone meal to ruminants is believed to be the most likely means of transmission of BSE. Regulations now prohibit this practice in Canada.
The on-farm investigation of the birth herd identified two feeds of interest, a dairy ration and a protein supplement.
Feed mill compliance. Review of the feed mill inspection records indicated that the feed mill that produced the dairy ration had a good Health of Animals Act compliance history.
The feed mill’s formula showed that ruminant meat and bone meal was used in the ration until July 1997 and discontinued when the Canadian feed ban was implemented in August 1997.
It was unlikely that the protein supplement was the source of exposure, since it would probably have been consumed before the index case had access.
The feed investigation concluded that meat and bone meal exposure, through feed, occurred prior to implementation of the Canadian feed ban.
Animal investigation. The agency’s animal investigation was designed to determine the herd of origin of the BSE-positive cow found in Washington state.
Through the Canadian health of animals ear tag, herd and registration records, it was determined that the animal was born April 9, 1997, on a farm in Alberta.
The herd records identified the index case’s sire, dam and Canadian born calves. Neither the dam nor the Canadian born calves were located in Canada.
The DNA of the brain of the index case, its hide (located by Canadian investigators working in Washington State with their U.S. counterparts), semen from its sire and DNA of one its offspring (born in the US) were compared. The results confirmed the identification of the animal.
Herd dispersal. The infected cow was part of a herd of 113 dairy animals that was dispersed. Seventeen were moved in September of 2001 to multiple destinations; one went to auction; three were slaughtered for the owner’s use; 11 went to a dairy farm; and 81, including the index case, were exported in September, 2001 to a heifer breeding operation in Wash.
At the heifer breeding operation, three animals were kept, eight animals were moved to a heifer raising operation in Wash., and 70 animals, including the index case, were moved to Mabton, Wash., where the case of BSE was found.
Twelve killed. In total, 12 animals were destroyed and tested in Canada and test results for all 12 were negative for BSE.
In the May 2003 BSE case, approximately 2,700 animals from the investigations in Alberta and Saskatchewan were destroyed.
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