[en] The global area of GM crops has increased from 2 million ha in 1996 to 59 million ha in 2002. The principal crops modified for agronomic input traits such as herbicide tolerance and/or insect resistance are soyabean, maize, cotton, and canola. These crops are all used extensively in livestock production rations as either energy and/or protein feed resources. They are included either in the form of whole crop, (eg. maize silage); a specific crop component (eg.maize grain); or as co-products (eg. oilseed meals, or maize stover). One of the main concerns expressed over the use of GM feed ingredients arose from the fact that some GM crops contained genes coding for antibiotic resistance which were used as markers in the initial plant selection process. The other main concern was linked to the possible accumulation of transgenic DNA and protein in milk, meat and eggs derived from animals receiving diets containing GM feed ingredients and over possible human and animal health risks. These concerns resulted in renewed interest in the fate of DNA and protein in the gastrointestinal tract. Key issues in this debate will be addressed in the paper