Contribution of cobalamin analogues to plasma vitamin B12 concentrations in cattle
Halpin, C.G.; Harris, D.J.; Caple, I.W.; Petterson, D.S.
Research in Veterinary Science 37(2): 249-251
1984
ISSN/ISBN: 0034-5288 PMID: 6438747 Document Number: 232250
Plasma vitamin B-12 concentrations in cattle were analysed by a radioisotope dilution assay using pig intrinsic factor and a microbiological assay using Euglena gracilis. Both assays provided similar results for samples of cattle plasma containing vitamin B-12 concentrations ranging from 0.07 to 3.60 mu g/litre (r = 0.95, P<0.001). The addition of excess cobinamide in the radioisotope dilution assay to block non-specific binding in the intrinsic factor preparation due to the presence of R-type binders, was used to determine the presence of cobalamin analogues. Cobalamin analogues accounted for up to 50% of the total vitamin B-12 concentration in samples of plasma from cows but were virtually undetectable in plasma from sheep.