In Great Britain the use of animal-derived protein in animal feeds has recently been subject to restrictions (The Bovine Spongiform Encephalopathy Order 1988 and subsequent orders), including a prohibition on the use of animal protein produced from ruminant carcases in feed given to ruminants. More generally, livestock producers are increasingly demanding more detailed information about the ingredients included in the compound feeds they purchase, and may stipulate that meat and bone meal derived from particular animal species is not used in their feed. In order that compliance with these legal and commercial requirements can be monitored and enforced, it is important that feed manufacturers, their customers and the regulatory authorities should have recourse to a means of identifying the species from which animal protein, when present in a feed, is derived.