Study On Relationship Between Degradation Characteristics Of Carbohydrates And Proteins And Their Molecular Structure And Lignin Monomers Of Several Feed

The production performance of ruminants is affected by many reasons such as the quality of roughage.At present,the research on the quality of roughage mainly focus on chemical components,there is few researches on the effect of molecular structure of feed components on quality.Lignin is the most difficult part of roughage to be digested and used by animals.The monomer structure of lignin may affect the degradation rate of roughage.Fourier transform infrared spectroscopy?FTIR?analysis technology is a fast,direct,non-destructive and non-invasive detection method which can be used to analyze the molecular structure of roughage.In this study,firstly,high boiling alcohol solvent method was used to e xtract lignin from different gramineae and legume roughages.Fourier transform infrared spectroscopy to analyze the extracted high boiling alcohol lignin,comparing gramineae and beans Differences in the lignin structure of the roughages,especially the ratio of the relative content of syringyl to guaiacyl unit?S/G?.Then,Then the traditional nutrient analysis method,nylon bag method,improved three-step in vitro method and Fourier transform infrared spectroscopy analysis were used to c ompare the nutrition composition,rumen degradation,protein intestinal digestion characteristics,and protein and carbohydrate molecular structures of gramineae and legume roughages.Finally,a protein and carbohydrate molecular structure and lignin monomer composition?S/G?were used to predict the nutrient composition and digestion characteristics of roughage.The experiment methods and results are as follows:The first part was the extraction and structural characterization of roughage lignin.Lignin of twenty-two roughage?11 grasses and 11 legumes?was extracted by high boiling alcohol solvent method.Fourier transform infrared spectroscopy?FTIR?analysis was used to characterize the structure of high boiling solvent lignin in roughage.The characteristic absorption peaks of each functional group of HBSL in feed samples mainly appeared in the fingerprint region of 1800-800cm^-1.The results showed that the HBSL of the sample showed the characteristics of lignin absorbance.Among the materials,the present absorption peaks could be preliminarily determined that the lignin of samples in this study were G-S-H type lignin.The infrared spectra of HBSL of the grass samples were observed in the bands around 1332 cm^-1 and 1258 cm^-1,respectively,which were typical absorptions of syringyl and guaiacyl units.The typical absorption at 1366-1317 cm^-1and 1258 cm^-1 can also be observed as syringyl and guaiacyl units.The S/G value of Elymus was significantly lower than the S/G values of other grass feed?p<0.05?.Except Lucerne,there was no significant difference in S/G value of HBSL among other varieties of Lucerne?p?0.05?,but it was higher than that of other legume materials.The second part of this trial was traditional nutrition analysis of roughage.In this study,traditional methods were used to determine the chemical composition of the grass and legume roughage.The results showed that the range of the dry matter?DM?content of legumes was wider than that of grasses.The crude protein?CP?content of legumes,especially the CP content of several lucerne,was higher than the CP content of grasses.The neutral detergent fiber?NDF?content of the grass feed is higher than that of most legume feed stuffs.The acid detergent fiber?ADF?content of legumes was slightly larger than that of grasses.There had difference among the acid detergent lignin?ADL?content of feeds of roughages.The neutral detergent insoluble protein?NDIP?and acid detergent insoluble protein?ADIP?content of gramineae was slightly higher than the NDIP and ADIP content of legume feedstuffs.The third part was the comparison of rumen degradation characteristics and protein intestinal digestibility of roughage.The in situ nylon bag method was used to determine the rumen degradation parameters of DM,CP,NDF and ADF of roughage,and the small intestine digestibility of rumen non-degradable protein was determined by an improved three-step in vitro method.The dry matter soluble fraction?S?of TFL2007 lucerne was the highest.The dry matter insoluble but potentially degradable fraction?D?of Leymus chinensis was the highest.The dry matter undegradable fraction?U?of Leymus chinensis was the lowest,while the undegradable fraction of soybean straw was the highest.The dry matter degradation rate of D fraction?Kd?of Leymus chinensis was the lowest.The dry matter degradation rate of D fraction of lucerne was the highest.Generally,there was no significant difference in the S,D and U fraction of the dry matter between Gramineae and legumes?p?0.05?.The Kd and EDDM fraction of legumes was significantly higher than that of Gramineae?p<0.05?.The crude protein soluble fraction of soybean stalk was the highest,but not significantly different from most materials?p?0.05?.The crude protein insoluble but potentially degradable fraction of TFL2007 lucerne was the highest.The crude protein insoluble but potentially degradable fraction of soybean stalk was the lowest.The D fraction of the legumes was significantly higher than the gramineous feed?p<0.05?.The rumen undegradable fraction of crude protein?RUP?of gramineous feed was significantly higher than that of legumes,while the rumen effectively degradable fraction of crude protein?EDCP?of gramineous feed was significantly lower than that of legumes.The soluble fraction of NDF of Leymus chinensis was the lowest.The insoluble but potentially degradable fraction of soybean stalk NDF was the lowest,which was significantly lower than other feedstuffs?p<0.05?.For the undegradable fraction of NDF,soybean stalk is the highest and oat grass was the lowest.The S and U fraction and degradation rate of D fraction of neutral detergent fiber of gramineous was significantly lower than legumes,but the D fraction and rumen effectively degradable fraction of neutral detergent fiber?EDNDF?was significantly higher than legume feed?p<0.05?.The highest ADF soluble fraction was Quanneng lucerne,and the lowest was soybean stalk.The ADF insoluble but potentially degradable fraction of Leymus chinensis was the highest and the lowest was red bean straw.The undegradable fraction of ADF of Elymus was the lowest.The ADF undegradable fraction of soybean stalk was the highest.The ADF effective degradation fraction of Bromegrass was the highest,and soybean stalk had the lowest ADF effective degradation fraction.Generally,except for the D fraction,which was significantly lower than the Gramineae,the S,U fraction and Kd were higher than the Gramineae,and the difference was significant?p<0.05?,but rumen effectively degradable fraction of acid detergent fiber?EDADF?was not significantly different from the Gramineae?p?0.05?.The rumen undegradable protein of Leymus chinensis had the highest intestinal digestibility?Idg?.The small intestine digestibility of rumen undegradable protein from Glycyrrhiza uralensis was the lowest.The small intestine digestibility of rumen undegradable proteins in legumes varies widely.The results showed that the small intestine digestible protein of legume feeds had a wider range than that of gramineae,and the difference between feedstuffs were obvious.The fourth part was the comparison of protein and carbohydrate structure of roughage.FTIR analysis was used to determine the protein and carbohydrate structures of roughages.Spectral analysis results showed that:within the region of the relevant spectral band of the protein(ca.1705-1472 cm^-1),the highest peak area of the amide I band was Peanut vine.Comparing to the gramineae,the difference in the area of the amide II band among legume feedstuffs was more obvious.The area ratio of amide I to amide II band of Millet straw was significantly higher than that of other feeds except peanut vine?p<0.05?and the area ratio of Amide I to Amide II of Tumu was the lowest.The height ratio of amide I to amide II band of peanut vine was significantly higher than that of other feedstuffs.The spectral of secondary structure of protein,?-helix and?-sheet,showed that height of the?-helix of lucerne was the highest,and the height of?-sheet of peanut vine was the highest.The height ratio of?-helix to?-sheet of wild barley and Leymus chinensis was the highest,and the height ratio of?-helix to?-sheet of Tumu was the lowest.The area of cellulosic compounds of corn stalk was the highest and area of cellulosic compounds of TFL2007 lucerne was the lowest.The area of struc tural carbohydrate of peanut vine was the highest.The total carbohydrate peak area and the height of three sub-peaks(cr.1150cm^-1,1100 cm^-1,and 1060 cm^-1)of corn stalk had the highest peak height.The area ratio of cellulosic compounds to total carbohydrate of soybean stalk was significantly higher than other feedstuffs?p<0.05?,and the area ratio of rice straw was the lowest.The ratio of area of structural carbohydrates to total carbohydrates of rice straw was the lowest,and that of Glycyrrhiza pallidiflora was the highest.The peak area ratio of legumes is higher than that of grasses.The peak area ratio of the fiber complex to structural carbohydrates of wild barley is the highest,and that of peanut vine was the lowest.Last part of this trial was analysis of relationship between molecular structure of roughage and nutrition composition and digestive characteristics.This study used the PROC CORR procedure of SAS9.4 to perform correlation analyses,and then used the stepwise method of the PROC REG procedure to perform multiple regression analysis.The area of amide I,area and height ratio of amide I to amide II band and the peak height of the?-helix of the protein structure could predict protein insoluble but potentially degradable fraction of gramineae.The NDIP content of legumes can be predicted by the area of amide I band,the height of amide II band,the area ratio of amide I to amide II band,and the height of?-sheet?predicting coefficient was 0.66?.The S/G ratio of gramineae showed positive correlation with the dry matter content of the feed and negative correlation with the ADL content of the feedstuffs.The S/G ratio was negatively correlated with the content of DM,NDF,ADF and ADL of Legumes.S/G showed a negative correlation with the soluble fraction of feed dry matter,a negative correlation with the dry matter undegradable fraction of feedstuffs?r=-0.782,p<0.0001?and a positive correlation with the dry matter insoluble but potentially degradable fraction?r=0.798,p<0.0001?of Legumes.S/G was positively correlated with insoluble but potentially degradable fraction of legume NDF?r=0.753,p<0.0001?and negatively correlated with undegradable fraction?r=-0.748,p<0.0001?.The area of total carbohydrate showed a positive correlation with the ADF degradation rate of D fraction in gramineae,while S/G was negatively correlated with the ADF soluble fraction of gramineae?r=-0.683,p<0.0001?.S/G had negative correlation with undegradable fraction?r=-0.812,p<0.0001?,and positive correlation with the insoluble but potentially degradable fraction of legume feed ADF.The area ratio of cellulosic compounds,structural carbohydrates and total carbohydrates to each other and the S/G could be used to estimate the NDF conte nt of legumes.The area ratio of cellulosic compounds to structural carbohydrate and S/G can be used as important parameters in ADF content estimation model?determination coefficient was 0.68?.The area of cellulosic compounds and structural carbohydrate,ADL content and S/G could be used as predictors to predict rumen degradation parameters(S_DM,Kd _DM,S_NDF,Kd _NDF,S_ADF and Kd _NDF)of some gramineae.The area ratio of cellulosic compounds to structural carbohydrate and ADL contents could be used to estimate the dry matter rumen soluble fraction of legume.The area ratio of cellulosic compounds to structural carbohydrate,ADL and S/G can be used as predictors in the D_DM,U_DM and U_ADF prediction models of legumes.The coefficients of determination are 0.85,0.87and 0.90.Therefore,this study concluded as:After analysis,the extracted high boiling alcohol lignin retains the basic structure of lignin in the feed.The high boiling alcohol lignin of the 22 roughages in the experiment are all GSH type lignin,but the relative content ratio of syringyl and guaiacyl between the feeds is different.In this experiment,the nutritional value of the feed was different,and the legume roughage nutrients had a higher digestibility.The differences in the molecular struct ure of protein and carbohydrates of roughages reflect the nutritional value of the feed to a certain extent and affect the digestion characteristics.The ratio of the relative content of syringyl and guaiac yl based monomers of lignin can be used as a parameter to predict the digestibility of roughage to a certain extent,and it will affect the degradation of carbohydrates in feed.The nutritional value and digestion characteristics of feed can be evaluated by using Fourier transform infrared spectroscopy to quickly determine the molecular structure of roughage.