Study On Reducing Methane Production In The Rumen Of Dairy Cows By Fermented Total Mixed Ration

Ruminant methane emissions are huge,accounting for 73% of animal husbandry.Methane production in ruminants will not only cause energy loss,but also cause environmental pollution.Therefore,this experiment was conducted to study the effect of fed total mixed ration(FTMR)on rumen methane production in dairy cows.In Experiment 1,the effects of CO fermentation of Lactobacillus plantarum and cellulase on nutritional characteristics and bacterial composition of total mixed ration(TMR)were studied.In Experiment 2,the effects of fermented total mixed diet on rumen microbial diversity and methane production were studied in vitro.In Experiment 3,the effects of FTMR on production performance and methane production of dairy cows were evaluated.The results are as follows:Experiment 1: Effects of fermentation treatment on fermentation quality,bacterial diversity and rumen degradation rate of TMR with two concentrate to roughage ratiosThe experiment was designed as four treatments:(1)TMR group with 40:60 ratio of concentrate to roughage(TMR HF);(2)TMR group with 60:40 ratio of concentrate to roughage(TMR HC);(3)TMR group with 40:60 ratio of concentrate to roughage was used for fermentation(TMR FHF);(4)TMR group with 60:40 ratio of concentrate to roughage was used for fermentation(TMR FHC).Five replicates were processed in each group,Anaerobic fermentation at room temperature for 30 days.The fermentation quality,bacterial diversity and rumen degradation rate of TMR were determined.The results showed that fermentation could significantly reduce the p H of TMR(P<0.05),and increase the concentration of ammonia nitrogen and the molar ratio of acetic acid and lactic acid(P<0.05).The results showed that fermentation could significantly increase the relative abundance of Lactobacillus and decrease the relative abundance of Acetobacter(P<0.05).In addition,the rumen degradation rates of TMR dry matter,crude protein and neutral detergent fiber were significantly increased by fermentation(P<0.05).Experiment 2: Effects of two concentrate to roughage ratios of TMR on in vitro fermentation parameters,methane production and rumen microbial diversityThe experiment group was the same as experiment 1.The real-time in vitro fermentation system(Jilin Academy of Agricultural Sciences,model: Qtfxy-6)was used.Four groups of TMR were used as the fermentation substrate.Each group had three replicates,and the experiment was repeated three times.Methane concentration was measured and recorded every 6 minutes,and p H,ammonia nitrogen,bacterial protein,volatile fatty acid concentration and rumen protozoa,bacteria and archaea diversity were measured at 24 hours of in vitro fermentation.The results showed that rumen ammonia nitrogen concentration,cell protein concentration and propionic acid molar ratio were significantly increased by fermentation;The p H,acetic acid molar ratio,ethylene propylene ratio and methane concentration were significantly decreased(P<0.05).The order of methane production from low to high was TMR FHC group<TMR FHF group<TMR HC group<TMR HF group.Principal component analysis of protozoa showed that there were differences between TMR FHC group and TMR HC group.The protozoa species of TMR FHF group and TMR HF group were similar.The results showed that the main position of TMR HF group was Dasytricha(34.04%),followed by Endodinium(7.73%),Isotricha(3.66%),Metadinium(1.81%)and Cephalospolix(0.87%).The dominant protozoa was Dasytricha(17.49%)and Endodinium(2.61%)in TMR FHF group;The majority of TMR HC group was Dacytricha(56.59%),followed by Endodinium(11.39%)and Isotricha(9.21%).The dominant protozoa was Dasytricha(12.21%),Endodinium(9.18%)and Isotricha(2.97%)in TMR FHC group.Principal component analysis of bacteria showed that there were differences in bacterial species between TMR FHF group and TMR HF group.The bacteria species of TMR FHC group and TMR HC group were similar.The relative abundance of four groups of bacteria was detected,Compared with TMR HF group,Pseudobutyrivibrio and Butyrivibrio in TMR FHF group decreased from 22.98% and6.11% to 13.31% and 2.62% respectively,and Succinicasticum increased from 1.08% to 1.34%(P<0.05).Compared with TMR HC group,Pseudobutyrivibrio and Butyrivibrio in TMR FHC group decreased from 40.80% and 4.63% to 14.28% and 3.71% respectively,and Succinicasticum increased from 0.54% to 1.14%(P<0.05).In addition,the Chao index,observed species index and Shannon index of bacterial community in fermentation TMR group were significantly higher than those in TMR group,while the Simpson index was significantly lower than that in TMR group(P<0.05),indicating that fermentation can increase the species and quantity of rumen bacteria.Principal component analysis of Methanogens showed that there were differences in methanogenic bacteria between TMR group and TMR group.In TMR HF group,Methanobrevibacter(88.38%)was the main methanogenic bacteria,followed by Methanoplanus(3.73%)and Methanosphaera(1.41%).In TMR FHF group,Methanobrevibacter(55.18%)and Methanoplanus(33.26%)were the dominant methanogens;In TMR HC group,Methanobrevibacter(77.34%)was the main methanogenic bacteria,followed by Methanoplanus(9.95%).In TMR FHC group,Methanobrevibacter(92.54%),Methanoplanus(2.04%)and Methanosphaera(0.97%)were the dominant methanogens.The abundance of Methanobrevibacter in TMR HF group was significantly lower than that in other groups(P<0.05).In addition,the observed species index and Shannon index of methanogens community in TMR group were significantly lower than those in TMR group(P<0.05),indicating that fermentation can reduce the number and species of methanogens.Experiment 3: Effects of fermented TMR on performance and methane production of dairy cowsOn the basis of Experiment 1 and Experiment 2,20 Holstein cows with 40:60 concentrate to roughage ratio were selected for feeding experiment.According to the lactation days and milk yield,they were divided into two groups:(1)TMR group(feeding cow TMR)and(2)FTMR group(feeding cow FTMR).After two weeks of adaptation period,the feeding experiment was conducted for 8 weeks.The results showed that compared with TMR group,milk yield,energy corrected milk yield,standard milk yield,milk fat percentage and feed efficiency of ftmr group were significantly increased(P<0.05),while methane yield,rumen p H,acetic acid molar ratio,butyric acid molar ratio and ethylene propylene ratio were significantly decreased(P<0.05).In addition,rumen ammonia nitrogen concentration,total volatile fatty acid concentration and molar ratio of propionic acid in ftmr group were significantly higher than those in TMR group(P<0.05)To sum up,the conclusions of this study are as follows:(1)Fermentation can improve the rumen degradation rate of crude protein and neutral detergent fiber by changing the bacterial composition of TMR,thus improving the nutritional value of the diet.(2)TMR fermentation can change the rumen fermentation type from acetic acid type to propionic acid type,and reduce the species and quantity of rumen protozoa and methanogenic bacteria,thereby reducing methane production.(3)TMR fermentation can improve production performance and reduce methane production.