The Detection of Animal Derived DNA in Stockfeed Existing Test Improvement and Screening Test Evaluation

Summary

Bovine spongiform encephalopathy (BSE) is a fatal degenerative disease affecting the central nervous system of cattle. The disease was first reported in the UK in 1986, with up to 100,000 cattle affected by 1993. The practice of feeding meat and bone meal (MBM) to cattle has been implicated in the spread of BSE through the cattle population. More than 80 cases of a variant of the fatal Creutzfeldt-Jakob disease (nvCJD), which affects humans, have been reported in the UK. This human disease has been linked etiologically to BSE.

In 2000, the Scientific Steering Committee advising the European Commission on BSE-related issues rated Australia in the lowest risk category for having cattle infected with the BSE agent (GBR level 1). However, an important component of the risk management measures required for Australia to maintain such a status is the ability to monitor and audit for the presence of animal-derived tissue in stockfeed. Compliance with Australia's ruminant feed ban needs to be monitored at a number of levels from imported stockfeed through to domestic stockfeed production. In each case, it is desirable to have a testing regime that is 'fit-for-purpose' as the testing requirements for imported stockfeed differ slightly to those for domestic stockfeed.

Currently, the only animal material that may be fed to ruminants is tallow, gelatin and milk or milk products of Australian or New Zealand origin. Importation of animal-derived stockfeed material, other than fishmeal, is currently only permitted from New Zealand. This study involved further validation of the PCR method previously developed by the Australian Government Analytical Laboratories (AGAL). The assay was assessed against stockfeed ingredients that are excluded from the current Australian ban such as tallow, gelatin and milk powder and against MBM that has been rendered to the stringent conditions required of the European Union (EU). Rapid screening tests for detecting animal protein in stockfeed have been evaluated and a procedure developed to monitor for inhibitory substances in stockfeed that could give rise to a false negative result.