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The use of transgenic crops as feeds for ruminant animals has prompted study of the possible uptake of transgene fragments by ruminal micro-organisms and/or intestinal absorption of fragments surviving passage through the rumen. The persistence in buffered ruminal contents of seven different recombinant DNA fragments from GM rapeseed expressing the5-enolpyruvylshikimate-3-phosphate synthase(EPSPS) transgene was tracked using PCR. Parental and transgenic (i.e. glyphosphate-tolerant; Roundup Ready®, Monsanto Company, St Louis, MO, USA) rapeseed were incubated for 0, 2, 4, 8, 12, 24 and 48 h as whole seeds, cracked seeds, rapeseed meal, and as pelleted, barley-based diets containing 65 g rapeseed meal/kg. The seven transgene fragments ranged from 179 to 527 bp and spanned the entire 1363 bp EPSPS transgene. A 180 bpribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) small subunit fragment and a 466 bp 16S rDNA fragment were used as controls for endogenous rapeseed DNA and bacterial DNA respectively. The limit of detection of the PCR assay, established using negative controls spiked with known quantities of DNA, was 12·5 pg. Production of gas and NH3was monitored throughout the incubation and confirmed activein vitrofermentation. Bacterial DNA was detected in all sample types at all time points. Persistence patterns of endogenous (Rubisco) and recombinant (EPSPS) rapeseed DNA were inversely related to substrate digestibility (amplifiable for 48, 8 and 4 h in whole or cracked seeds, meal and diets respectively), but did not differ between parental and GM rapeseed, nor among fragments. Detection of fragments was representative of persistence of the whole transgene. NoEPSPSfragments were amplifiable in microbial DNA, suggesting that transformation had not occurred during the 48 h incubation. Uptake of transgenic DNA fragments by ruminal bacteria is probably precluded or time-limited by rapid degradation of plant DNA upon plant cell lysis.

Subacute ruminal acidosis (SARA) is a common digestive disorder in dairy cows characterized by prolonged periods of undesirably low rumen pH (5.8) and is caused by the accumulation of volatile fatty acids in rumen. This disorder damages the ruminal mucosa, causes diarrhea, reduces dry matter intake (DMI), and can result in anorexia and death. In this study, nonlactating dairy cows were fed diets predisposing them to a high risk (HR; n = 6) or a low risk (LR; n = 6) for experiencing SARA. The goal was to investigate differences in antimicrobial resistance selection, proliferation, and characterization of Escherichia coli strain types among the two treatment groups. Fecal samples were used to isolate total, tetracycline-resistant (Tet(r)), and ampicillin-resistant E. coli, and selected isolates were examined. We found reduced total (1.2-fold) and Tet(r) (1.4-fold) E. coli in HR cows. Low ampicillin-resistant E. coli shedding was detected from both HR (0.22 colony forming unit/g) and LR (0.46 colony forming unit/g) cows. Overall, 39 pulsed-field gel electrophoresis (PFGE) profiles and 13 antibiotic resistance profiles (phenotypes) were identified from the total isolates examined (n = 144). The LR cows exhibited diverse genotypes (22 PFGE profiles) clustering into seven restriction endonuclease digestion pattern clusters (REPCs) within total and Tet(r) E. coli. In comparison, isolates from HR animals showed increased genotypic relatedness (16 PFGE profiles and 13 REPC with comparable phenotypes). From both HR and LR cows, no significant differences in the detection of a particular phenotype were observed (p0.05), and tet(A) allele was frequently detected among isolates from HR (45.2%) and tet(B) from LR (36.6%) cows. Changes in fecal E. coli genotypes should be explored further for its usefulness as an indicator for SARA since dairy cows are a reservoir of diverse E. coli strain types. Our results elucidate phenotypic and genotypic differences in fecal E. coli shed between HR and LR cows.

The aim of this study was to examine the prevalence and distribution of Escherichia coli O157:H7 lineage-specific polymorphism assay (LSPA) 6 genotypes from cattle (n = 313) and clinical human (n = 203) isolates from northern and southern Alberta, Canada, to understand possible associations of genotypes with host and geographic location. The majority of cattle isolates (feedlot and dairy) typed as LSPA-6 111111 (72.2%), with proportionately higher LSPA-6 222222 (19.4%) than other LSPA-6 genotypes (10.7%). Clinical human isolates also typed primarily as LSPA-6 111111 (90.1%), but a higher percentage of genotypes (6.8%) other than LSPA-6 222222 (3.1%) was observed. A significantly higher frequency of LSPA-6 111111 in southern Alberta cattle (P < 0.0001) and a significant difference in LSPA-6 genotypes between human versus feedlot cattle from northern Alberta (P < 0.0001) were detected. LSPA-6 211111 genotype was third and second most common in cattle and humans, respectively, and several new LSPA-6 genotypes (n = 19) were also discovered. Despite avoiding over-representation of isolates from specific farms or outbreaks, higher strain diversity among cattle by pulsed-field gel electrophoresis (PFGE; 50 genotypes) in contrast to human (9 PFGE genotypes) isolates was observed. The majority of cattle (74.4%) and human (90.6%) isolates were susceptible to the antimicrobials tested. Within resistant cattle isolates, sulfisoxazole-tetracycline resistance was common (62.5%) and was accounted for by the presence of sul1 and sul2, and tet(A) and tet(B) determinants. An association between LSPA-6 and PFGE genotypes but not between geographic location and PFGE genotype for both hosts was evident.