Transgenic plants in poultry nutrition

Abstract

Studies on genetically modified (GM) feedstuffs for poultry (and other livestock species) have not added any substance to public concerns in Europe about their safety for human or bird health. The compositions of maize lines engineered for insect resistance (Bt-maize) or herbicide tolerance (glyphosate) and herbicidetolerant soybean have all proved to be essentially indistinguishable from their conventional counterparts. Consequently, and not surprisingly, comparative feeding studies with broilers and layers in which conventional maize (50 to 78%) or soybeans (27%) were replaced in feeds by transgenic varieties, also have failed to show differences of any significance in production parameters. These data indicate that feeding studies with target livestock species contribute very little to the safety assessment of crops engineered for input traits that have little or no detectable effect on chemical composition. However, comparative growth studies made with broiler chicks, particularly sensitive to any change in nutrient supply or the presence of toxic elements in their feed, can be used to screen for any unintended adverse consequence of the recombinant event not detected by compositional analysis. This does, however, depend on whether the GM plant can be matched to a parental line or another suitable control and its suitability for inclusion in broiler diets. The discovery that DNA fragments from the digestive tract can be found in the tissues of animals evoked interest in the fate of ingested transgenes. Plant DNA derived from feed has been detected in the muscle, liver, spleen and kidneys of broilers and layers, although not in eggs. However, no fragments of transgenic DNA or its expressed protein have been found to date in poultry meat or eggs or in any other animal tissues examined.