Daniel E Wachenheim

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An in vitro assay was used to examine biotransformation of toxic Senecio jacobaea pyrrolizidine alkaloids (PA) in ovine, bovine, and caprine rumen contents. Pyrrolizidine alkaloids were analysed by high performance liquid chromatography, and the rates of the alkaloid biotransformation were determined. The microbiological "Most Probable Numbers" technique(More)
Ingestion of pyrrolizidine alkaloids, naturally occurring plant toxins, causes illness and death in a number of animal species. Senecio jacobaea pyrrolizidine alkaloids cause significant economic losses due to livestock poisoning, particularly in the Pacific Northwest. Some sheep are resistant to pyrrolizidine alkaloid poisoning, because ovine ruminal(More)
Ruminococcus flavefaciens strain C94, a strictly anaerobic, cellulolytic ruminal bacterial species, was grown either in batch or continuous cultures (cellobiose limited or nitrogen limited) at various dilution rates. Washed cell suspensions were incubated anaerobically at 39 degrees C without nutrients for various times up to 24 h. The effects of starvation(More)
Anaerobic production of extracellular polysaccharide (EP) was examined, using a previously uncharacterized, obligately anaerobic rumen isolate, Butyrivibrio fibrisolvens nyx, which produced an EP that was rheologically similar to xanthan gum. The main objectives were to determine the nutritional requirements and conditions which promoted EP production by(More)
Titanium citrate (TC) or L-cysteine-sodium sulfide was added as a reducing agent to buffers and agar media used for enumeration of bacteria from rumen contents of high-forage-fed steers. Approximately equal colony counts were found on TC and L-cysteine-sodium sulfide-reduced media with rumen contents taken 8 h postfeeding, when active bacterial growth was(More)
Mathematical models are useful for describing microbial growth, both in natural ecosystems and under research conditions. To this end, a rate expression that accounted for depletion of nutrients was used to derive the logistic function model for batch cultures. Statistical analysis was used to demonstrate the suitability of this model for growth curve data.(More)
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