| Ferulic and p-coumaric acids are widely distributed in graminaceous plant cell wall, they account80%of total phenolic acids, including mainly ester and ether forms.phenolic acids in the plant cell wall might limited the degradation of cell wall. The present study mainly focused on the degradation and metabolism of plant cell wall by lacting cows.Experiment One, The present study esteablished the HPLC method to tested the ester and ether linked ferulic acid,p-coumaric acid in the feed. The result showed that the content of both acids differed among the feeds by testing the feeds commonly used in the dairy farm, even in the same feeds. The contents of ether linked ferulic acid (FAeth), ester linked p-coumaric acid (PCAest), ether linked p-coumaric acid (PCAeth) and p-coumaric/ferulic ratio was positively correlated with feed ADL content, indicating they could reflect the cell wall ligninfication extent.Experiment Two, Rumen fluid was collected via rumen cannulae after feeding to research the variation of ester linked and free form of ferulic acid,p-coumaric acid in the rumen fluid. The result showed that the concentration of ester linked p-coumaric was far higher than that of free form, the concentration of p-coumaric acid was higher than ferulic acid in both ester and free form. The average concentration of FAest, PCAest, free FA and free PCA was0.53ug/ml,1.81ug/ml,0.02ug/ml and0.05ug/ml, respectively. It could speculated that the release of FAest in the primariy cell wall began2h after feeding, while the release of PCAest in the second cell wall might begin4h after feeding, and the release of ferulic acid by microorganism was slower than that of p-coumaric acid.Experiment Three, This research studied the in vitro dry matter disappearance (IVDMD), gas production and dynamic of gas production, FAest and PCAest disappearance and their metabolize, the correlation between feed phenolic acid content and disappearance of feed or ester phenolic acids in12feeds. The result showed that FAeth content and PCA/FA were negatively correlated with IVDMD, gas production, rate of gas production, digestibility of FAest and PCAest. At the same time, FAeth content hand negative effect on the rate of gas production.The digestibility of FAest (0.502～0.966) was higher than PCAest digestibility (0.195-0.880) in each feed. The released FA and PCA from feeds were nearly all metabolized by rumen microorganisms. The contents of phenolic acids in the culture fluid were very low, and existed mainly in ester and free form, contrary to the ester form, the content of FAest in the culture fluid was far lower than free FA.Experiment Four,64milking Holstein dairy cows were chose and divided into4groups, each feed different TMR:typical ration used in scale dairy farm, replaced Chinese wild ryegrass with alkali treatment corn stover,50%corn saliage and7%concentrate. The research was to research the digestibility of ester linked phenolic acids in total digestive tract. The digestibility of DM, NDF, ADF, FAest and PCAest were significantly difference among the TMR. Unlike in vitro study, the FAeth concentration in the ration was positively correlated with FAest digestibility, the concentration of PCAest was positively correlated with DM, NDF and ADF digestibility. PCAeth content was also positively correlated with FAest digestibility. PCA/FA ratio was positively correlated with DM, PCAest digestibility, but it was negatively correlated with FAest digestibility. This might due to the difference of the microorganism caused by forage, and this influence was greater for PCAest digestion than that of FAest.Five,45milking Holstein dairy cows were chosed and divided into three groups, and feed different TMRs, in which the forages were corn stover, rice stover and alfalfa hay to research the transform of ester linked phenolic acids from feed to milk. The results showed that most of ferulic acid and p-coumaric acid were metalized in the rumen, only trace ester linked ferulic acid (1.9×10-3%) and p-coumaric acid (1.0×10-3%) could be transform into the milk. And the content of FA and PCA in the milk was only22.9ng/ml and32.5ng/ml for ferulic acid and p-coumaric acid. |
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