The Metabolism of Red Clover Isoflavones in the Rumen of Dairy Cows
[Objective]The purpose of this experiment was to study the stability and metabolism of red clover isoflavones in rumen.[Methods]In in vivo experiment,3 fistulated Holstein cows were selected and fed 2 g of red clover extract(isoflavone content 22.91％)into the rumen before morning feeding.Rumen fluid was collected at 0,0.5,1,2,4,8,12 and 14 h,respectively,and HPLC was used to analyze the isoflavone contents.In in vitro rumen fermentation,3 treatment groups were set up,0.1 g/120 mL(high-dose group),0.01 g/120 mL(low-dose group),and no red clover extract group(control group),with 5 replicates in each group,and fermented at 39 ℃.Rumen fluid was collected at 0,0.5,1,2,4,8,12 and 14 h,respectively.HPLC was used to analyze the contents of isoflavones.[Results]In in vivo experiments,biochanin A and formononetin were metabolized at 14 and 8 h,respectively.After 2 h,the metabolite S-equol was present in the rumen.The half-lives of biochanin A and formononetin were 1.02 and 2.25 h,respectively,while those of daidzein and genistein were 3.38 and 0.77 h,respectively.In in vitro experiment,the half-lives of the four isoflavones in the high-dose group and the low-dose group were different.In the high-dose group,the half-lives of biochanin A,formononetin,daidzein and genistein were 2.45,0.70,12.62 and 5.74 h,respectively.In the low-dose group,the half-lives of biochanin A,formononetin,daidzein and genistein were 2.82,0.87,13.11 and 3.45 h,respectively.[Conclusion]Red clover isoflavones were unstable in the rumen of dairy cows and could be catabolized by microorganisms.The half-lives of the main isoflavones,biochanin A and formononetin were all less than 4 h.It was speculated that the metabolic end products of the two isoflavones were S-equol and ethylphenol,respectively.
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