The Study Of Different NDF Level Diet On The Apparent Nutrients Digestibility And The Structure And Composition Of Rumen Microorganisms In Goats

This experimentwas mainly studiedthat the effects of dietary neutral detergent fiber?NDF?on apparent digestibility,rumen fermentation and microbial structure and composition of goats.The experiment adopted 3*3 Latin square design,six healthy male Nubian black goats with an average age of about 6 months and an average body weight?28.33 ± 3.77 kg?were selected as experimental animals in this study.The experiment was divided into three treatment groups according to NDF level,that were Low NDF level group?LN group:NDF value=35.01%?,medium NDF level group?MN group:NDF value=40.10%?and high NDF level group?HNgroup:NDF value=45.16%?,respectively.Each treatment group had six sheep,each sheep was a repeat.In the guarantee of feeding conditions under the equal nitrogen and equal energywere fed under the three NDF levels of diets.The experiment is divided into three periods,each experiment period last 20 days,including adaption period?14days?,metabolic trial?6days?.The effect of dietary NDF level on feed utilization rate was assessed by metabolic experiment.At the end of each metabolic test,the rumen fluid of each goat was sampled,individually.And then extracted the total rumen microbial DNA.The universal primers for bacteria?515F:5'-GTGCCAGCMGCCGCGGTAA-3';806R:5'-GGACTACHVGGGTWTCTAAT-3'?and the specific primers for archaea?Arch519F:5'-CAGCCGCCGCGGTAA-3';Arch915R:5'-GTGCTCCCCCGCCAATTCCT-3'?were used to amplify the bacteria V4 region and the archaea V4-V5 region of 16SrRNA gene.We carried out sequencing of the amplified products of bacteria and archaea by using the modified Illumina HiSeq 250PE sequencing platform.The results were analyzed by bioinformatics software such as QIIME.The difference of production performance,apparent digestibility of nutrients,rumen fermentation parameters,and the relative abundance of microbes at different levels was analyzed by using the Latin square mathematical model method.The experiment results are as follows:1.The effects of dietary NDF levels on growth performance and apparentdigestibility of nutritional components in goats:There was no significant effects?P>0.05?on initial body weight?IBW?,final body weight?FBW?,average daily gain?ADG?and dry matter intake?DMI?of goats between in three treatment groups?P>0.05?.The ADG ofLN and MN groups were significantly higher than that of HN group?P<0.05?,but there no significant difference between LN group and MN group?P>0.05?.The weight ratio of LN and MN groups were significantly lower than that of HN group?P<0.05?,but there was no significant difference between the LN group and MN group?P>0.05?.There were no significant differences in GEI,DEI,UE,ME and DE/GE,ME/GE,ME/DE between the three treatment groups?P>0.05?.However,the excretion of manure?FE?in MN group was significantly higher than that in the other two groups?P<0.05?.There were no significant differences in the apparent digestibility of DM,OM and CP between the three treatment groups?P>0.05?and decreased with the increase of NDF level.The apparent digestibility of EE in LN group was significantly higher than that in MN group and HN group?P<0.05?.The apparent digestibility of CF and NDF in HN group was significantly higher than that in LN group and MN group?P<0.05?.2.The effects of dietary NDF level on rumen fermentation parameters of goats:The pH value of goat rumen fluid between the three treatment groups varied between 6.50-7.00 and the difference was not significant?P>0.05?,but increased with the increase of NDF level.Rumen NH3-N concentration,HN group was significantly lower than the LN group and MN group?P<0.01?,and decreased with the increase of NDF level.There was no significant difference in rumen acetic acid,propionic acid,butyric acid and total VFA concentration between the treatment groups?P>0.05?.Except for the acetic acid with increasing NDF level increases,the other was with the increase of NDF levels decreased.The ratio of acetic acid to propionic acid increased with the increase of dietary NDF level,and the LN group was significantly lower than that of HN group?P<0.05?.There was no significant difference between the MN group and the other two groups?P>0.05?.3?The effects of dietary NDF level on the structure and composition of rumen bacteria and archaea in goats:?1?.At the phylumlevel of bacteria,there was no significant difference in the relative abundance of all species between the three treatment groups?P>0.05?,and the first three dominant bacteria were Bacteroidetes,Firmicutes and Proteobacteria.At the genus level,the first two dominant genera in the three treatment groups were Prevotella₁ and Rikenellaceae_RC9_gut_group,respectively.At genus level,the relative abundance of Prevotellaceae_UCG-001,Prevotellaceae-UCG-003,Ruminococcaceae_NK4A214_group,Ruminococcaceae_UCG-005 and Ruminococcaceae_UCG-014 showed an increased changes with the increase of NDF level,and the HN group was significantly higher than the other two groups?P<0.05?,but there was no significant difference betweenthe other two groups?P>0.05?.The relative abundance of SP3-e08 and Lachnoclostridium₁0 showed a decrease with the increase of NDF level,and the HN group was significantly lower than the other two groups?P<0.05?,but there was no significant difference between the other two groups?P>0.05?.The relative abundance of Succiniclasticum in LN group was significantly higher than that in the other two groups?P<0.05?,but there was no significant difference between the other two groups?P>0.05?.The relative abundance of[Eubacterium]_ruminantium_group in LN group was significantly higher than that in HN group,but there was no difference compared with MN group.The relative abundance of Lysinibacillus,Bacillus and Phyllobacterium in MN group was significantly higher than that in the other two groups?P<0.05?,the relative abundance of Victivallis was very significantly higher than that of the other two groups?P<0.01?,but there was no difference between the other two groups.There was no significant difference in the relative abundance of other strains between the two groups?P>0.05?.There was no significant difference in Chao1 and Shannon index between the treatment groups?P>0.05?,but the Observed species index of LN group was significantly higher than that of the other two groups?P<0.05?.?2?.Atthe phylumlevel of archaea,there was no significant difference in the relative abundance of all species in the three treatment groups?P>0.05?,and the dominant phylum was Euryarchaeota.Atgenus level,Methanobrevibacter,Candidatus_Methanomethylophilus and Candidatus Methanoplasma were the dominant genera of the three treatment groups.The relative abundance of Methanobrevibacter in LN group was very significantly lower than that in the other two groups?P<0.01?,but the relative abundance of Candidatus_Methanomethylophilus and Candidatus_Methanoplasma was significantly higher than that of the other two groups?P<0.05?,these archaea were no significant difference between the other two groups.There was no significant difference between the three treatments in the other genera?P>0.05?.The Chaol,Shannon and Observed_species indices of LN group were significantly higher than those of the other two groups?P<0.05?,but there was no significant difference between the other two groups?P>0.05?.In summary,when the NDF level varied from 35%to 45%,the average daily gain,feed utilization rate,apparent digestibility of EE and ammonia nitrogen concentrationwere significantly decreased with increasing NDF concentration,the apparent digestibility of CFand NDFand rumen acetic acid propionic acid ratio were significantly increased.The dominant archaea in the rumen of goats was the Euryarchaeota,and the dominant bacteria were Bacteroidetes,Firmicutes and Proteobacteria.When the level of NDF in diets varied between 35%and 45%,the structure and composition of goat rumen flora at the phylum level were not significantly affected,but the relative abundance of certain bacteria and major archaea were significantly affected.