§ Mr. Ron Davies
To ask the Minister of Agriculture, Fisheries and Food on what scientific basis he has decided that beef from animals slaughtered over the age of 30 months should not be offered for human consumption; and what other considerations underlay his decision to select 30 months as a critical age for this purpose. 
§ Mrs. Browning
[holding answer 22 April 1996]: In the absence of detectable infectivity in tissues of clinically affected cattle other than brain, spinal cord and retina, the Spongiform Encephalopathy Advisory Committee considered that the greatest risk to consumers of clinically normal animals would be associated with exposure to central nervous tissue. This is precisely why these tissues are designated as specified offals. Nevertheless, after giving further consideration to the slaughtering/butchering process, it was felt that risk of exposure could be reduced further by requiring changes to certain procedures, such as removal of bones so that in doing so tissues contaminated with spinal cord were also removed, as would visible nerves and lymph nodes. It was, however, unnecessary to apply this to all cattle. This decision was partly based on the pathogenesis of scrapie in sheep and mice, where infectivity is only detectable in the central nervous system approximately half-way through the incubation period, subsequently rising to a peak at the time of clinical disease. That evidence is increasingly supported by the on-going pathogenesis experiment of cattle, where infectivity has so far not been detected in CNS up to 18 months post-infection. The mean incubation period of BSE in naturally infected animals is five years and the appropriate mid-point would therefore be 30 months. Clearly in cattle older than 30 months there will be increasing levels of infectivity in the CNS of infected animals, and more of them are likely to be approaching the onset of clinical disease prior to slaughter.
The use of 30 months as a watershed was originally introduced in relation to exports of bone-in beef in 1995 under EC rules and was taken up by the Spongiform Encephalopathy Advisory Committee in its advice to Ministers on 20 to 24 March respectively that the meat from animals over 30 months of age should be deboned in licensed premises and the obvious nervous and lymphatic tissue removed and treated as specified bovine offal. In view of the concern expressed by the committee about the meat from animals above this age and the difficulties of introducing an immediate requirement for all of this meat to be deboned, it was decided during the consultation period that a ban should be introduced on the use of this meat for human consumption until such time as the consultation period was ended and suitable arrangements for deboning were introduced. Subsequently, it was decided a European Union level that, in view of the collapse of demand for beef from older cattle, the prohibition on the use of 145W meat from older animals in the human and animal feed chains should be maintained.