| In this experiment,sweet sorghum straw was selected as the raw material to study the effect of rumen fluid pretreatment and anaerobic fermentation time on sweet sorghum straw’s nutritional composition,feeding value,fermentation quality,microbial quantity,aerobic stability and microbial diversity and other related indicators.and provide data support for the rational development and utilization of grass-fed livestock forage resources.The experiment adopted a two-factor completely random design with 3×4(fermentation days×rumen fluid addition amount)factor treatment structure.One control group(CK,0%rumen fluid,0 m L/100g)and three rumen fluid groups(R1,10%rumen fluid,10 m L/100g;R2,20%rumen fluid,20 m L/100g;R3,30%rumen fluid,30 m L/100g),3 replicates for each experimental group.Sterile distilled water and rumen fluid were mixed evenly and then added to the straw to adjust the moisture content to about 75%,and anaerobic fermentation was continued for 45 d.Samples(3 time points×4treatments×3 replicates,36 bags in total)were sampled and analyzed on the 0th,15th and 45th days after fermentation,respectively.The test results are as follows:Experiment 1:Eeffects of rumen fluid treatment on nutritional components and feeding value of sweet sorghum strawOn the 0 d,15 d and 45 d,the quality of sweet sorghum straw before and after anaerobic fermentation was weighed,and samples were taken after opening the bag and mixing.Take about 200 g of fermented sweet sorghum straw from each bag,put it in an oven at 65°C,dry it for 48 h,calculate the moisture content,pulverize it,pass through a 40-mesh sieve,put it in a plastic tank,seal and store it,and use it to determine the nutritional composition,feeding value,effective energy value and other relevant indicators.The results showed that:1)With the prolongation of anaerobic fermentation time and the increase of rumen fluid addition,the dry matter(DM)content,ether extract(EE)content and organic matter(OM)content of sweet sorghum straw showed an overall downward trend,while crude protein content decreased.(CP)content,crude ash content(Ash)content,non-fibrous carbohydrate(NFC)content and dry matter loss rate(DML)showed an overall upward trend,with significant differences(P<0.05).2)With the extension of anaerobic fermentation time and the increase of rumen fluid addition,the content of neutral detergent fiber(NDF),acid detergent fiber(ADF),cellulose(CL),hemicellulose(HC)and total cellulose(TC)of sweet sorghum straw showed a downward trend,and the biodegradation potential(BDP)showed an upward trend,with significant differences(P<0.05).3)With the prolongation of anaerobic fermentation time and the increase of rumen fluid addition,the dry matter intake(DMI),digestible dry matter(DDM),total digestible nutrients(TDN),relative feed intake of sweet sorghum straw The overall value(RFV)and relative forage quality(RFQ)showed an upward trend,with significant differences(P<0.05).4)With the prolongation of anaerobic fermentation time and the increase of rumen fluid addition,the digestible energy(DE),metabolizable energy(ME),maintenance net energy(NE_m),weight gain net energy(NE_g)and milk production of sweet sorghum straw The overall net energy(NE_L)showed an upward trend,with significant differences(P<0.05).Experiment 2:Effects of rumen fluid treatment on the fermentation quality and aerobic stability of sweet sorghum strawOn the 0 d,15 d and 45 d,the anaerobic fermented sweet sorghum straw was bagged and mixed,and then sampled.Carry out on-site sensory quality analysis,fermentation quality analysis,microbial quantity analysis and aerobic stability analysis.The results showed that:1)With the extension of the anaerobic fermentation time and the increase of the amount of rumen fluid,the smell,structure,color and total score of the sweet sorghum straw showed an overall upward trend,and the difference was not significant(P>0.05),and with the extension of the anaerobic fermentation time,the difference between the odor and the total score was significant(P<0.05).2)The p H,ammonia nitrogen(AN)content,ammonia nitrogen/total nitrogen(AN/TN)and water-soluble carbohydrate(WSC)content of sweet sorghum straw showed an overall downward trend with the prolongation of anaerobic fermentation time and the increase of rumen fluid addition.The difference was significant(P<0.05).3)With the prolongation of anaerobic fermentation time and the addition of rumen fluid,the lactic acid(LA)content and acetic acid(AA)content of sweet sorghum straw showed an overall upward trend,and the overall lactic acid/acetic acid(LA/AA)showed a downward trend.The difference was significant(P<0.05).4)With the prolongation of anaerobic fermentation time and the addition of rumen fluid,the content of lactic acid bacteria(LAB)in sweet sorghum straw showed an overall upward trend,while the content of yeast and mold showed a downward trend,the content of lactic acid bacteria was significantly different(P<0.05).5)On the 0 d,3 d,6 d,and 9d of aerobic exposure,the p H showed an overall upward trend,and the differences were all significant(P<0.05).The addition of rumen fluid effectively slowed down the increase of p H;DM content The overall trend was decreasing,and the differences were all significant(P<0.05).The addition of rumen fluid effectively accelerated the decline rate of DM.6)With the prolongation of fermentation time and the increase of rumen fluid addition,the days of aerobic stability were prolonged,the days of aerobic stability were in the order of 45 d of fermentation more than 15 d of fermentation more than 0 d of fermentation,and the days of aerobic stability in the R3 group were more than 9 d.Experiment 3:Effects of rumen fluid treatment on microbial diversity of sweet sorghum strawOn the 0 d,15 d and 45 d,high-throughput sequencing analysis of bacterial microorganisms from anaerobic fermentation of sweet sorghum straw was performed.The results showed that:1)with the extension of fermentation time and the increase of rumen fluid concentration,the number and species of bacterial microbiota in each treatment could be significantly increased,and the alpha diversity of bacterial microorganisms was significantly different(P<0.05).2)At the phylum level,the relative abundance of dominant flora in each treatment group was the highest,Firmicutes(4.25%～98.95%),and the abundance of Firmicutes in R3 group was higher than that in other groups(P<0.05).3)At the genus level,the highest relative abundance of dominant bacteria in each treatment group was Lactobacillus(0.81%～29.26%),and the abundance of Lactobacillus in R2 and R3 groups was higher than that in CK group(P>0.05).In summary,with the extension of fermentation time and the increase of rumen fluid addition,on the 45d of fermentation,R3 group(30%rumen fluid,30 m L/100 g)can significantly reduce the fiber content of sweet sorghum straw,improve the nutritional composition,improve the feeding value,increase the effective energy value,effectively improve the fermentation quality,prolong the aerobic stability time and increase the microbial diversity of beneficial bacteria,It can provide theoretical and experimental basis for the rational development and utilization of sweet sorghum straw and other crop straw. |
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