F01002 (CS0118): Effects of commercial-scale processing on the integrity of DNA in animal feed
Monday 27 September 2004
This project aims to assess the effects of commercial-scale processing on the integrity of DNA in animal feeds.
Study Duration: January 1999 to December 2000
Contractor: Agricultural Development and Advisory Service (ADAS)
Background
The project examined the effect of commercial-scale processing on the degree of DNA fragmentation in conventional animal feed materials. Since any fragment of DNA smaller than 500 base pairs (bp) is very unlikely to contain a functional gene, this fragment size was taken as the criterion for estimating the effect of processing on animal feed DNA.
Transgenes per se were not investigated and no genetically modified feeds were included for study.
Research Approach
Approximately 41 animal feed samples were studied which included unprocessed feeds (generally used as control samples in order to demonstrate the effect of the processing method), samples from sequential points within a given process and finished animal feed products.
Results and findings
Introduction
A key question in assessing new genetically modified crops is whether it is possible for novel genetic material present in animal feed materials to transfer to bacteria in the gastro-intestinal tract of animals fed such material. The Advisory Committee on Novel Foods and Processes (ACNFP, 1996) concluded that the likelihood of transfer is low, but could not be ruled out altogether.
In order for foreign DNA to transfer from animal feed and become expressed in a bacterium a number of steps must occur. The first step involved in facilitating such a phenomenon is that feed material must contain fragments of DNA large enough to contain the potentially functional gene.
The wide range of feed materials included in the diets of animals may be subject to various methods of processing involving, for example, heat, pressure and grinding. These physical and chemical processes may have the effect of fragmenting feed DNA to sub-optimal units. However, the degree to which this occurs during commercial-scale processing of animal feeds is not known.
The present project therefore examined the effect of commercial-scale processing on the degree of DNA fragmentation in conventional animal feed materials.
Results
The extraction of DNA from unprocessed feed ingredients (including some samples used as controls which would not otherwise be fed to animals without processing, e.g. whole soya beans) resulted in DNA fragments of approximately 23 kb in length. This fragment size is also the typical length of DNA yielded from undamaged plant cells. Therefore, the possibility was eliminated that DNA degradation in processed samples might be as a result of the laboratory extraction procedure, rather than the commercial-scale processing regime itself.
DNA extracted from the processed feed samples was either non-degraded (approximately > 12 kb) and/or fragmented to varying degrees. Samples which produced fragmented DNA (soya bean meal (extracted), rapeseed (expeller), flaked maize, wheat feed, cotton seed meal, rice bran and sunflower meal (extracted)) all contained DNA fragments large enough to contain a potentially functional gene.
Dissemination information
Final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency tel: 020 7276 8181/8182 or email: library&info@foodstandards.gsi.gov.uk
Contact: For any enquiries concerning this research project, please contact the relevant Programme contact or email science@foodstandards.gsi.gov.uk