Assessment Of Fiber Digestibility And Energy Metabolizability Of Boer Goats' Diet And Research On The Relationships Among Structure Of The Rumen Microorganism From Boer Goats And Them

Utilization of nutrients in ruminants has significant differences across individual animals,which is closely associated with structure and composition of rumen microorganism.In order to compare rumen microbial diversity of Boer goats with the different digestibility of crude fiber(CF)and energy metabolic rate,the two experiments were perfonned as follow.Exp.1:Assessment of crude fiber digestibility of Boer goats' diet and study on relationships between rumen microbial structure of Boer goats and CF digestibilityBoer goats(n=19)with similar live body weight and physiological condition were fed with the same diet.The entire test session lasted 20 days including 14-day pre-treatment period and the digestion phase for 6 days.During digestion period,all feces and urine were collected and then preserved in low temperature freezer.Finally,rumen liquid was sampled for DNA extraction in the next morning of experiment finished.After analysis of the digestibility of CF and calculation of their mean and standard deviation(SD),screening of high fiber digestibility(HFD,HFD>0.5 SD above the mean,n=5)and low fiber digestibility(LFD,LFD<0.5 SD below the mean,n=5)groups were performed.Results showed that the digestibility of CF between HFD and LFD was extremely significant difference(P<0.01).DNA extraction of microbial communities from rumen content per sample was performed according to the protocols of DNA Extraction Kit(TIANamp Stool DNA Kit),regarding the DNA extract as template DNA.The universal primers for bacteria were used to amplify the V4-V5 regions of 16S rRNA gene.And subsequently the PCR-based amplification,high-throughput sequencing on the Illumina MiSeq 300PE sequencing platform and bioinformatics analysis were performed.The results indicated that:1)At phylum level,Bacteroidetes?Firmicutesand and Proteobacteria were the dominant bacteria phyla between HFD and LFD,but they had no significant difference,respectively(P>0.05).The relative abundances of Chloroflexi and Crenarchaeota were significantly higher in LFD than HFD(P<0.05),respectively.2)The relative abundance of Acidobacteria-6?Actinobacteria.Anaerolineae?Gammaproteobacteria and Bacilli at class level showed greatly lower in LFD than HFD(P<0.05).While there are extremely significant differences(P<0.01)in Thaumarchaeota between groups;3)There were significantly higher trend(P<0.05)in the four order-level bacteria(iiil-15?SBR1031?Enterobacteriales and Lactobacillales)of LFD than HFD.And there were greatly significant differences(P<0.01)in Nitrososphaerales and WD2101(higher in LFD than HFD).4)Prevotellaceae was the most dominant bacteria at family level in the two groups and significant differences(P<0.05)were also found with Enterobacteriaceae and Piscirickettsiaceae,Nitrososphaeraceae,Bacteroidaceae,Enterococcaceae,Lactobacillaceae and Veillonellaceae between groups(higher in LFD than HFD).5)69 genus-level bacteria with more than 0.1%average relative abundance in two groups were detected among 857 genera from two groups.And Prevotella which had no significant differences between groups was the most dominant genus in the two groups.However,the six genus-level bacteria were detected(*Enterobacteriaceae,Bacteroides,5-7N15,Other belonging to Enterococcus,Lactobacillus and Veillonella)with significant differences(P<0.05)in two groups(higher in LFD than HFD).In addition,*Piscirickettsiaceae and Candidatus Nitrososphaera belonging to Crenarchaeota showed remarkably significant differences between the groups(higher in LFD than HFD)(P<0.01).Regression analysis between CF digestibility and the relative abundance of microorganism demonstrated that there was a positive correlation between CF digestibility per sample and the relative abundance of Bacteroidaceae(Family)?Lactobacillus(Genus)?Bacteroides(Genus)?5-7N15(Genus)and Kaistobacter(Genus),individually.However,the negative relationship had been built between CF digestibility per sample and the relative abundance of Crenarchaeota(Phylum)?Thaumarchaeota(Class)?Nitrososphaerales(Order)?Lactobacillaceae(Family)?N itrososphaeraceae(Family)?*Enterococcaceae(Genus)?Veillonella(Genus)and*Piscirickettsiaceae(Genus),respectively.Exp.2:Assessment of energy metabolic rate of Boer goats' diet and research on relationships between rumen microbial structure of Boer goats and energy metabolic rateBoer goats(n=19)with similar live body weight and healthy body were fed the same diet.The test lasts 24 days covering 14-day pre-test period,6-day test period and 4 days for calorimetric trials.Feed intakes were recorded,and all feces and urine were collected during metabolism trial.Then methane and carbon dioxide migration and oxygen consumption were measured during the last 4 days of the test.In the next morning finishing the test,rumen content was sampled.After analysis of the energy metabolic rate and calculation of their mean and standard deviation(SD),screening of high energy utilization(HEU,HEU>0.5 SD above the mean,n=5)and low energy utilization(LEU,LEU<0.5 SD below the mean,n=5)groups were performed.Results showed that energy metabolic rate of the diet between HEU and LEU had significant difference(P<0.05).The analysis method of microbial flora diversity between HEU and LEU was the same as the Exp.1.The results showed that the relative abundances of 1 class-level bacteria(Bacilli),3 order-level bacteria(Lactobacillales,Bacillales and RB41),7 family-level bacteria(Enterococcaceae,Lactobacillaceae,Bacillaceae,Clostridiaceae,Sinobacteraceae,Shewanellaceae and Bacteroidaceae)and 5 genus-level bacteria(*Enterococcaceae(other,Lactobacillus,Bacillus Clostridium and Ruminococcaceae)belonging to the Firmicutes,Shewanella of the phylum-level Proteobacteria and 3 genus-level bacteria(Bacteroides,Bacteroidaceae,Prevotella)attaching to Bacteroidetes were higher in LEU than HEU,respectively(P<0.05).However,there were no significant differences between two groups and no correlations between energy metabolic rate and the relative abundances of all bacteria,individually.In conclusion,some bacteria from rumen content of goats with different CF digestibility and energy metabolic rate have significant differences,some of which(including 1 phylum-level bacteria,2 class-level bacteria,3 family-level bacteria and 7 genus-level bacteria)have significant correlations with CF digestibility per sample.However,no significant correlations have been found between the relative abundance of bacteria and energy metabolic rate per sample.