These findings agree with results from a wild boar study where cry1Ab fragments of up to 420 bp were detected in gastric contents but no fragments greater than 211 bp were found further down the GIT. In the same study, a small rubisco gene fragment was found throughout the GIT and a small fragment of cry1Ab was found at very low frequency in the jejunal contents. The smallest fragment we chose to detect in our study was 149 bp; therefore, smaller cry1Ab fragments may have been Y-27632 dihydrochloride ROCK inhibitor present in digesta distal to the stomach but remain undetected. Similar to Wiedemann et al., and Chowdhury et al., we detected a small rubisco fragment in small intestinal, cecal and colon digesta. Chowdhury et al., also detected a small cry1Ab fragment in 40 kg pigs fed Bt maize for 28 days. The majority of studies, both in monogastric and ruminant species, have failed to detect transgenic DNA beyond the gastrointestinal barrier. Furthermore, our group were previously unable to detect a 211 bp fragment of the transgenic cry1Ab gene in the organs or blood of pigs fed Bt maize for 31 days. In agreement with these findings, a longer feeding period of 110 days did not influence the ability of cry1Ab to translocate across the intestinal barrier of pigs, as neither the 211 or 149 bp cry1Ab fragments were detectable in the blood, liver, muscle, or kidneys in the present study. Mazza et al., however, detected a 519 bp cry1Ab fragment in the plasma, liver, kidney and spleen of piglets fed Bt maize for 35 days, although the gene��s smallest functional unit was never detected. Likewise, a 278 bp fragment of the cp4epsps transgene from Round-up Ready canola was found in the liver and kidneys of pigs, however, the prevalence was extremely low. The transfer of endogenous plant DNA from the GIT into blood and organs appears to occur spontaneously in nature. Our findings are similar to those reported in calves and fallow deer where small fragments of the multiple copy endogenous chloroplast rubisco gene were detected in liver, kidney and spleen. Guertler et al. and Mazza et al. also detected fragments of the multiple copy endogenous chloroplast zein gene in organs of deer and pigs fed Bt maize, respectively. We were previously unable to detect fragments of the single copy endogenous chloroplast sh2 gene in the organs or blood of pigs fed Bt maize for 31 days and similar results were found when pigs were fed Bt maize for a longer duration in the present study. These findings suggest that copy number is the rate limiting step in the traceability of transgenic DNA. Also, the low detection frequency of the cry1Ab gene in the ileum and the absence of cry1Ab gene detection distal to the ileum may SB431542 company account for the lack of detection of the single copy cry1Ab gene in animal tissues and blood. Similar to our findings in weanling pigs, the Bt toxin was detected in the stomach, cecum and colon digesta but not in the organs or plasma of pigs fed Bt maize for 110 days.