Document Detail

Factors that determine rates of cyanogenesis in bovine ruminal fluid in vitro.
MedLine Citation:
PMID:  2166729     Owner:  NLM     Status:  MEDLINE    
Strained ruminal fluid was collected from cattle fed five diets at two locations to determine in vitro rates of cyanogenesis from the glycosides amygdalin, prunasin and linamarin. Rates of dissociation for the corresponding aglycones, benzaldehyde cyanohydrin and acetone cyanohydrin, also were determined. Hydrogen cyanide (HCN) in ruminal fluid was determined with a modified method of HCN analysis that independently measured the overall rate of cyanogenesis and the nonenzymatic dissociation of cyanohydrins, the intermediate products in the degradation of cyanogenic glycosides to HCN. Rate of dissociation of cyanohydrins in ruminal fluid was pH-dependent, with high rates of dissociation (as expressed by the rate constant or half-life of the reaction) occurring at pH greater than 6 and slower rates at pH 5 to 6. Cyanohydrin dissociation was most rapid when cattle were fasted for 24 to 48 h and ruminal pH was high; rate of dissociation was much slower during feeding and digestion. When the glycosides were examined, highest rates of cyanogenesis (mg HCN.liter-1.s-1) were observed after a 24-h postprandial period. Hence, cattle are most susceptible to poisoning by cyanogenic plants when the pH of ruminal fluid is elevated (for rapid dissociation) and also when the activity of microbial beta-glucosidase is adequate for rapid hydrolysis of glycosidic bonds. Rates of cyanogenesis were higher when ruminal inocula were from cattle fed fresh alfalfa or cubed alfalfa hay rather than grain or long hay. Rates of HCN production were slowest using inocula from cattle fed grain; rates for the three glycosides were negligible at the 3 and 6 h postprandial sampling times.(ABSTRACT TRUNCATED AT 250 WORDS)
W Majak; R E McDiarmid; J W Hall; K J Cheng
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  Journal of animal science     Volume:  68     ISSN:  0021-8812     ISO Abbreviation:  J. Anim. Sci.     Publication Date:  1990 Jun 
Date Detail:
Created Date:  1990-09-18     Completed Date:  1990-09-18     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8003002     Medline TA:  J Anim Sci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1648-55     Citation Subset:  IM    
Agriculture Canada Research Stations.
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MeSH Terms
Amygdalin / metabolism
Cattle / metabolism*
Glycosides / metabolism*
Hydrogen Cyanide / metabolism*
Hydrogen-Ion Concentration
Nitriles / metabolism
Plants, Toxic
Rumen / metabolism*
Reg. No./Substance:
0/Glycosides; 0/Nitriles; 0/cyanogenic glycosides; 138-53-4/prunasin; 29883-15-6/Amygdalin; 554-35-8/linamarin; 74-90-8/Hydrogen Cyanide

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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