Effects Of Phenolic Acid And Lignin Monomer On Rumen Degradation Of Feed

Ferulic acid and p-coumaric acid are linked to the lignin monomer through an ester bond or an ether bond,and the content of ferulic acid and p-coumaric acid and the form thereof and the proportion of the lignin monomer directly affect the degradation of the feed.In this experiment,ten kinds of feeds of whole soybean,rice husk,bran,alfalfa,pine needle powder,bromegrass,oats,leymus,wild barley and corn stover were collected,and their conventional nutrients and rumen degradation were measured.As well as the cell wall structure components phenolic acid(ferulic acid and p-coumaric acid)and lignin monomer,the content of dry matter,organic matter,neutral detergent fiber,acid detergent fiber,and acid detergent lignin in the feed were determined by reference to AOAC.The total ferulic acid and total p-coumaric acid in the feed were extracted by 4 mol·L-1 NaOH at 170℃ for 2 h;the ester bond ferulic acid and ester bond were used to extract coumaric acid.The mol·L-1 NaOH was subjected to alkaline hydrolysis at a constant temperature of 39℃ for 24 h;the lignin monomer was extracted by nitrobenzene oxidation.The phenolic acid and lignin monomers were quantified by high performance liquid chromatography.The rumen-fed cows were used to determine the degradation rate of the feed in the rumen at 3,6,12,24,30,48 and 72 h and the 288 h poorly soluble neutral detergent fiber content.This study aimed to provide a theoretical basis for the prediction of feed degradation in the rumen by exploring the correlation between conventional nutrients and their cell wall components and the degradation rate of feed in the rumen.The test results were as follows:1 Rumen degradation rate of phenolic acid in cell wallIn terms of effective degradation rate,the average of the ester bond in the feed to coumaric acid(41.56%)and total p-coumaric acid(49.91%)was lower than that of the ester bond ferulic acid(54.80%)and total ferulic acid.(53.24%).The content of phenolic acid in pine needle powder,alfalfa and soybean was lower(251.45 mg·kg-1,728.5 mg · kg 1 and 403.54 mg · kg-1),but the degradation rate of alfalfa and whole plant soy phenolic acid was higher.The degradation rate of pine needle powder phenolic acid was low.2 The effect of lignin and cell wall components on feed degradation rateThe lignin content of two legume forages(11.73%/DM)was significantly higher than that of several grasses(7.24%/DM),while the content of phenolic forage(33377.79 mg·kg-1)was significantly higher.For legume forage(930.27 mg·kg-1),the degradation rate of leguminous forage components was higher than that of gramineous forage(dry matter,72.75%vs.57.41%;organic matter,62.76%vs.51.65%,neutral detergent fiber 54.31%vs.47.55%,acid detergent fiber 46.2%)Vs.42.40%).3 Regression model for predicting feed degradation rate(1)The rumen degradation rate(DMD and OMD)of the dry matter and organic matter of the feed were both neutral detergent fiber(NDF),acid detergent fiber(ADF),acid washed lignin(ADL),acid-insoluble ash(AIA),and there was a significant negative correlation between the content of coumarin/ferulic acid(Pca/FA)and lignin monomer(S,G or H).The multiple regression equation was:DMD=88.06+0.42ADL-0.54Ash-4.66AIA-4.24(Pca/FA)-0.002S(R2=0.994,P<0.01).OMD=125.58+0.22NDF-1.23Ash-3.83AIA-0.003Pcaeth-15.32(S/G)-0.004G(R2 = 0.998,P<0.01).(2)The rumen degradation rate(NDFD,ADFD and ADLD)of NDF,ADF and ADL in feed were significantly negatively correlated with their AIA,Pca/FA and S monomer contents.The multiple linear regression equation was:NDFD=62.09-3.86AIA-0.007H(R2=0.911,P<0.01)ADFD=89.99+0.48ADF-7.57Ash+1.03ADL-0.009Pcaest+25.77(Pca/FA)-24.38(S/G)-0.084H-0.015G+0.017S(R2=0.996,P<0.01),ADLD=23.04-1.26Ash+0.48HL+0.30CL-0.0008Pcaest-0.001S(R2=0.974,P<0.01).(3)NDF(iNDF)with no rumen degradation in feed 288 h was significantly positively correlated with Ash,AIA and ADL.The multiple regression equation was:iNDF=7.18+0.81Ash+3.85AIA+2.2ADL-13.31(Pca/FA)-0.001 FAest + 0.009 Pcaeth(R2 =0.9967,P<0.01).The results showed that the degradation of feed in the rumen was affected by the ratio of acid-insoluble ash,acid-washed lignin,co-dosic acid to ferulic acid and H-cell content in lignin monomer composition.