Effects Of Interfacial Physical Properties Of Straw And Fermentation Broth On Nutrient Degradation And Rumen Microbial Adhesion

This study investigated the relationship between the specific surface area of straw and the surface tension of fermentation broth on the rumen microbial adhesion and nutrient degradation characteristics.The two specific surface area levels of corn stover were SSA1(0.664 m~2/g)and SSA2(1.135 m~2/g)respectively.Experiment 1:The effect of corn straw specific surface area on the dynamic degradation rate of nutrients at 6,12,24,36,48,72 h was studied by nylon bag method.Experiment 2:On the basis of the experiment 1,the effects of specific surface area on the microbial adhesion process were studied at 1,4,8,12,24,48 h.Experiment 3:Three surface tension levels ST1(56.17 mN/m),ST2(48.10 mN/m),and ST3(37.19 mN/m)were constructed.The method of vitro fermentation was used to study the effects of degradation and fermentation characteristics of surface tension on nutrients.Experiment 4:The method of vitro fermentation was used to study the surface tension levels of the fermentation broth of experiment 3,and the adhesion law of microorganisms at 2,6,12,and 24 h was studied.The main findings are as follows:1 The specific surface area of straw and its effect on the degradation characteristics in the rumenIncreasing the specific surface area of corn stover significantly(P<0.05)increased the rumen effective degradation rate of dry matter of corn stalk,neutral detergent fiber,crude protein,and the rapid degradation fraction of dry matter and crude protein.The degradation rate of acid detergent fiber was significantly(P<0.05)decreased.Specific surface area does not significant(P>0.05)the slow degradation fraction and rate constant of dry matter,neutral detergent fiber,crude protein,acid detergent fiber.2.The specific surface area of straw influenced microbial adhesionCompared to the SSA1 group,the chao1 index,the observed_species index,the PD_whole_tree index,the relative abundance of the Fibrobacter succinogenes genus,the Protozac_Negativicutes genus,the Selenomonadales genus,the Succiniclasticum genus,the Acidaminococcaceae family,the Deltatopoteobacteria genus,the Desulfovibrionaceae family,the Desulfovibrionales genus,the Bacilli family,the Lactobacillales order was significantly reduced(P<0.05)in the SSA2 group.Adhesion copies of Ruminococcus albus,Selenomonas ruminantium,Prevotella spp,Ruminobacter amylophilus,Genus metanobrevibacteria and microbial membrane size at the beginning of fermentation significantly increased(P<0.05)in the SSA2 group.The relative abundances of Fibrobacter,Fibrobacterales,Fibrobacteria,Fibrobacteres,Fibrobacteraceae,Spirochaetes,Spirochaetaceae,Spirochaetales,Spirochaetia,Treponema and Gammaproteobacteria were significantly increased(P<0.05).The specific surface area had no significant(P>0.05)effect on the copies of simpson,shannon and Total bacteria,Fungi,Ruminococcus flavefaciens,Methanogen,and Order methanobacteriales.3.Effect of surface tension of fermentation broth on in vitro fermentation characteristics and nutrient degradation rateThe dry matter degradation rate,neutral detergent fiber,acid detergent fiber degradation rate,and 72 h potential maximum gas production in ST3 group were extremely significant(P<0.01)lower than ST1 group and ST2 group.The shape parameters,gas production rate and initial substrate degradation rate of the ST3 group were extremely significant(P<0.01)higher than those of the ST2 group and the ST1group.The content of propionic acid,isobutyric acid,isovaleric acid,butyric acid,valeric acid and pH increased(P<0.01)with the decrease of surface tension.The total volatile fatty acid content decreased firstly and then decreased with the change of surface tension(P<0.05).The surface tension had no significant(P>0.05)effect on the acetic acid content and ammonia nitrogen concentration.4.Effect of surface tension of fermentation broth on microbial adhesionWith the decrease of surface tension,the copies of Total bacteria,Ruminococcus albus,Fibrobacter succinogenes and Fungi increased first and then decreased(P<0.05).The copies of Ruminococcus flavefaciens,Prevotella spp,and Prevotella ruminicola was decreased(P<0.01).The copies of Selenomonas ruminantium,Ruminobacter amylophilus and Methanogen had no significant(P>0.05)effect.PCA analysis showed that surface tension is an important factor affecting bacterial diversity.With the decrease of surface tension,bacterial diversity(chao1 index,observed_species index and PD_whole_tree index,Shannon index and simpson index)showed a decrease(P<0.05).The relative abundance of Bacteroidetes,Fibrobacteraceae,Fibrobacteria,Fibrobacterales,Fibrobacter,Fibrobacteres and Ruminococcaceae in the ST3 group were significantly lower(P<0.05)than in the ST1and ST2 groups.The relative abundance of the Firmicutes,Clostridia,Clostridiales,Lachnospiraceae,Lactobacillales,Bacilli,Streptococcaceae,Streptococcus,Proteobacteria,Gammaproteobacteria,Pseudobutyrivibrio,Butyrivibrio and Succinivibrionaceae in the ST3 group was significantly higher(P<0.05)than the ST1and ST2 group.The relative abundance of Paraprevotella,Ruminococcus and Prevotella was significantly(P<0.05)or extremely significant(P<0.01)with a decrease in surface tension and prolonged fermentation time.The relative abundance of Streptococcus,Pseudobutyrivibrio,Butyrivibrio and Succinivibrio was significantly increased(P<0.01)with a decrease in surface tension.5 Rumen microbial adhesion law in goat(in vivo VS in vitro)The copies of Ruminococcus albus,Ruminococcus flavefaciens,Fibrobacter succinogenes,Selenomonas ruminantium,Prevotella spp,Ruminobacter amylophilus,Methanogen,Genus metanobrevibacteria,Order methanobacteriales,Total bacteria and Fungi adhering to the surface of the straw was extremely significant(P<0.01).increase.The copies of Protoza showed a significant(P<0.01)reduction.From 1 h to 48 h,bacterial?-diversity index(chao1 index,observed_species index,and PD_whole_tree index)in vivo showed a significant(P<0.05)decrease.From 2-24h,the bacterial?-diversity index(chao1 index,observed_species index and PD_whole_tree index)in vitro was significantly decreased(P<0.01)with a prolonged fermentation time.At the level of the phylun,Bacteroidetes,Firmicutes,Fibrobateris,and Proteobacteris are the dominant bacteria in the in vivo and in vitro tests,accounting for more than 95%.The relative abundance of Fibrobateris in vitro was higher than that in vivo,while the relative abundance of Proteobacteris was lower than in vivo.At the genus level,the five dominant bacteria account for about 80%of the total bacteria.In vivo tests include Prevotella,Succiniclasticum,Butyrivibrio,Ruminococcus,and Fibrobacter.In vitro tests mainly include Prevotella,Fibrobacter,Streptococcus,and Pseudobutyrivibrio,Butyrivibrio.In vitro,except for the first increase and the decrease of Fibrobacter,the genus Prevotella,Streptococcus,Pseudobutyrivibrio and Butyrivibrio had no significant(P<0.05)changes.In vivo tests Ruminococcus and Fibrobacter increased(P<0.05),Prevotella first increase and then decreased,Succiniclasticum decreased,and Butyrivibrio first decrease and then increase.Prevotella,Fibrobacter,and Butyrivibrio are the dominant genus in vitro and in vivo.The in vivo tests of Succiniclasticum and Ruminococcus are higher than in vitro tests.The in vitro tests of Streptococcus and Pseudobutyrivibrio are higher than in vivo.In summary,increasing the specific surface area of straw can increase the rumen degradation rate of straw by increasing the adhesion of some nutrient-degrading bacteria and the rate of formation of microbial membranes.Decreasing the surface tension of the fermentation broth helps to increase the initial adhesion of microorganisms on the straw surface.When the surface tension of the fermentation broth is reduced from ST1(56.17 mN/m)to ST2(48.10 mN/m),the microbial and rumen fermentation characteristics of the straw surface can be improved.The rumen degradation rate of the fiber,when the surface tension of the fermentation broth is reduced to ST3(37.19 mN/m),can increase the number of initial adhesion microorganisms on the straw surface,but inhibits its growth and reduces the rumen degradation rate of the fiber.The initial microbial adhesion in vitro was lower than in vivo,and the vivo and the vitro tests were similar,but there were some differences in the number of dominant microorganisms.