Conventional and real-time polymerase chain reaction assessment of the fate of transgenic DNA in sheep fed Roundup Ready®rapeseed meal

Abstract

Conventional and real-time PCR were used to detect transgenic DNA in digesta, faeces and blood collected from six ruminally and duodenally cannulated sheep fed forage-based (F) or concentrate-based (C) diets containing 15 % Roundup Ready®(RR) rapeseed meal (n3). The sheep were adapted for 14 d to F or C diets containing non-GM rapeseed, then fed the RR diets for 11 d. On day 12, they were switched back to non-GM diets for a further 11 d. Ruminal and duodenal fluids (RF, DF) and faecal samples were collected at 3 or 4 h intervals over the 4 d immediately following the last feeding of GM diets. DNA was isolated from whole RF and DF, from the cell-free supernatant fraction, and from culture fermentation liquid. Blood was collected on days 1, 5 and 9 of feeding the RR rapeseed meal. The 1363 bp 5-enolpyruvylshikimate-3-phosphate synthase transgene (epsps) was quantifiable in whole RF and DF for up to 13 h, and a 108 bpepspsfragment for up to 29 h. Transgenic DNA was not detectable in faeces or blood, or in microbial DNA. Diet type (Fv.C) did not affect (P>0·05) the quantity of transgenic DNA in digesta. More (P < 0·05) transgenic DNA was detected in RF than in DF, but there was an interaction (P < 0·05) between sample type and collection time. In supernatant fractions from RF and DF, three different fragments of transgenic DNA ranging in size from 62 to 420 bp were not amplifiable.