Rumen microbial population characteristics and detection of transgenic DNA in rumen bacteria from sheep fed Bt176 maize for three years.

The use of genetically modified feeds and the level of public concern are increasing worldwide. One concern is the gene transfer to the rumen bacteria, but there is a lack of studies on this matter. Forty-four Bergamasca x Appenninica ewes were used in this 3-year study. Animals were divided in two groups and received hay ad libitum and either nontransgenic or Bt176 maize. Twelve, 20 and 12 ewes during the first, second and third year of the trial, respectively, were slaughtered 90 d after lambing and approximately 12 h after feeding. Rumen contents were collected and microbial populations were numerated. The presence of endogenous and transgenic DNA was searched for in DNA extracted from bacterial sub-populations grown for 7 (total and amylolytic) or 14 d (cellulolytic) in vitro. No difference was found between control and Bt176-fed ewes as far as bacterial numbers and protozoal genera distribution were concerned. Nor the 211 bp fragment from the CryIA(b) transgene or the 226 bp fragment of maize invertase gene was detected by PCR in the bacterial cultures. As expected, the rrs bacterial gene (1485 bp), used as a control, was found in all samples. These results show that a long time exposure to transgenic feed does not affect the rumen microbial populations tested and that the conditions of the gene rumen environment are likely to prevent bacteria from integrating recombinant DNA.