BSE controls final report, 20 December 2000, section 5, BSE

18. Most experts consider that, whatever the origin of the epidemic, the major route of transmission of BSE in cattle was through ruminant-derived meat-and-bone meal (MBM) in animal feed contaminated with the BSE agent. Epidemiological investigations in 1987-1988 identified the feeding of concentrate feed which contained MBM as a protein supplement as a common factor in all affected herds. It has since been substantiated by the dramatic decline in cases of BSE which followed the introduction of the ban on feeding MBM, with a lag of about five years (the average incubation period for the disease in cattle). The difference between dairy and beef suckler herds provides further evidence. Dairy animals were fed much greater quantities of MBM than were sucklers, and correspondingly have had a higher incidence of BSE: 61% of dairy herds have been affected as opposed to 16% of suckler herds. Most of the cases in beef suckler herds originated from dairy herds and were therefore weaned early and fed concentrates. It has also been shown that the disease can be transmitted to cattle in experimental conditions by feeding them infected brain material¹³. It has therefore been concluded that dietary MBM route was the major means of transmission to cattle. An independent study of the origin of the BSE epidemic is to be commissioned by the Government following publication of the BSE Inquiry report.

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13 - Wells et al, Infectivity in the ileum of cattle challenged orally with bovine spongiform encephalopathy Veterinary Record, 135, 40-41 (1994)