Effect Of Different Levels Of Tannin In Diets On Ruminal Bacteria Number And Methanogens Diversity In Sheep

In this study,fifteen 1.5-year-old sheep(45kg initial BW)were randomly divided into 3 groups with 5 sheep in each group.The basal diet supplemented without condensed tannin(CT)or with 2%CT and 4%CT constituted the group ?(control group),group ? and group ?,respectively.Tannin in the diet was originated from Caragana korshinskii.All treatments diets were is on itrogenous and isocaloric(concentrate:forage ratio of 4:6).The first 14 days of experiment were for adaptation and the official trial period is 20 days.The rumen fluid was collected at 0h(before morning feeding)and 6h(after the morning feeding)in 17 days and 18 days during the official trial period using rumen fluid oral sampler to extract the microbial DNA.The number of General bacteria,R.albus,R.flavefaciens,F.succinogenes,B.fibrisolvens,S.bovis,Prevotella,Anaerobic fungi,Methanogens,methaneobrevibacterium of sheep,as well as the expression of mcrA gene of sheep at 0h(before morning feeding)and 6h(after morning feeding)were detected using real-time quantitative PCR.Additionally,the diversity of methanogens and archaea in rumen fluid of 6 hours after morning feeding was measured by using the 16S rRNA high-throughput sequencing technology.The aim of the study was to explore the mechanism of tannin how to affect the rumen methane production in sheep from the perspective of the number of rumen microflora and the diversity of methanogens and to provide scientific basis for the exploitation and utilization of tannin-rich forage resources such as Caragana korshinskii as well as for the regulation of greenhouse gas emissions in ruminant production.The results showed that:(1)At 0h before morning feeding,the 2%tannin in the diet significantly reduced the number of R.flavefaciens(P ?0.05),and significantly increased the number of prevotella(P ?0.05).It also had a tendency to reduce the number of general bacteria,S.bovis,B.fibrisolvens,methanogens,methaneobrevibacterium.(P? 0.05).The 4%tannin in the diet significantly reduced the number of general bacteria,methanogens,methaneobrevibacterium,R.albus,S.bovis,B.fibrisolvens and F.succinogenes(P ?0.05).It also had a tendency to reduce the number of Prevotella.No significant difference was observed on the number of anaerobic fungi for group ? and ? as compared with control group(P? 0.05).(2)At 6h after morning feeding,the 2%tannin in the diet significantly reduced the number of general bacteria,R.albus,R.flavefaciens,B.fibrisolvens and F.succinogenes(P ?0.05).It also had a tendency to reduce the number of anaerobic fungi,S.bovis,methanogens,methaneobrevibacterium.The 4%tannin in the diet significantly reduced the number of General bacteria,R.albus,S.bovis,B.fibrisolvens,anaerobic fungi,F.succinogenes,methanogens,methaneobrevibacterium(P ?0.05),It also had a tendency to reduce the number of R.flavefaciens.No significant difference was observed on the number of Prevotella for group ? and ? as compared with control group(P? 0.05).(3)At 0h before morning feeding,The 2%and 4%tannin in the diet significantly reduced the expression of mcrA gene(P ?0.05).At 6h after morning feeding,The 4%tannin in the significantly reduced the expression of mcrA gene(P ?0.05).(4)At 0h before morning feeding and 6h after morning feeding,The 4%tannin in the diet significantly reduced the number of rumen protozoa in sheep(P ?0.05).It also had a tendency to reduce the number of protozoa in group ?.(5)The 4%tannin in the diet significantly reduced the abundance and community diversity of ruminal methanogens in sheep(P ?0.05).At the phylum level,the Euryarchaeota are dominant microorganism in the control group and group ?,the uncultivated bacteria is dominant microorganism in the group ?;At the family level,the Methanobacteriaceae are dominant microorganism in the control group and group?,the uncultivated bacteria is dominant microorganism in group III;At the genus level,uncultivated bacteria is the control group,methaneobrevibacterium are dominant microorganism in group? and ?.(6)The 2%and 4%tannin in the diet significantly reduced the abundance and community diversity of rumen archaea in sheep(P ?0.05).The Euryarchaeota is predominant phylum of each group,the Methanobacteriaceae is predominant family of each group and the methaneobrevibacterium is predominant genus of each group.