Effects Of Active Dry Yeast On Production Performance,Ruminal Fermentation And Bacterial Community Of Lactating Holstein Dairy Cow

The objective of the present study,using three active dry yeast levels in the total mixed ration?TMR,60:40?was to evaluate the effects of active dry yeast?live cell number?2.0×10¹11 CFU/g?on production performance,nutrients digestibility,serum indices,ruminal fermentation and bacterial community of lactating Holstein dairy cow.This study will supply guidance for the reasonable application of live yeast in practice.The first experiment:This experiment was conducted to investigate the effects of dietary supplementation of different active dry yeast levels on production performance,nutrient digestibility,serum indices and ruminal fermentation of lactating dairy cows.A total of Forty-five healthy Chinese Holstein lactating dairy cows were randomly assigned into 3 groups with 15 cows in each group based on the similar weight,parity,milk yield,lactation days and the content of milk,namely the control group Y₀ without ADY supplementation,trial group Y₂with 2 g/d and trial group Y₅with 5 g/d respectively,All diets were provided as TMR.The feeding trail period was 60 d,the pre-experimental period was 1 week.The results showed as fellows:1)compared with the control group Y₀,the dry matter intake,milk yield,4%fat correction milk production in trial group Y₅increased 1.23 kg/d,0.99 kg/d and 1.92 kg/d respectively?P<0.05?,The benefit per cow per day improved 3.25 yuan;2)compared with the control group Y₀,the content of propionate in rumen fluid of trial group Y₅significantly increased?P<0.05?,while the ration of acetate and propionate decreased?P<0.05?;3)compared with the control group Y₀,The dry matter intake and milk yield in trial group Y₂ was slightly increased?P>0.05?,milk composition and rumen fermentation parameters had no significant difference?P>0.05?,The benefit per cow per day improved 1.69 yuan;4)There was no remarkable effects of feeding active dry yeast on nutrients digestibility and serum indices of Holstein dairy cow?P>0.05?.Therefore,Adding 5g/?head/d?of active dry yeast could improve the function of ruminal fermentation,feed intake and production performance of lactating Holstein dairy cow.The second experiment:The effects of active dry yeast on rumen bacterial community diversity and composition were measured with high throughout sequencing technology in the second part of the study.The experimental animals and design are the same to the first part of the study.At the last day of the experimental period,three group total selected 38 head dairy cows,rumen liquid sample was taken before feeding,kept in-80?to preserve,then completed the total DNA extraction and PCR amplification.Sequencing of bacteria 16SrRNA was performed on the Illumina MiSeq,a total of 1679 OTUs and 784543Sequences were produced.The results showed as fellows:1)compared with the control group Y₀,adding ADY tended to increased Chao1 and Shannon index,which represent the rumen microbial richness and diversity?P>0.05?;2)On the levels of phylum,Bacterodetes,Firmicutes and Proteobacteria were the dominant microorganisms;on the levels of genus,Prevotella-1,Succinivibrionacea_UCG-001 and Prevotella-7 were the main dominant microorganisms;3)compared with the control group Y₀,the relative abundance of rumen Firmicutes in trial group Y₅increased,the relative abundance of rumen Proteobacteria decreased?P>0.05?;while Succinivibrionacea_UCG-001 significantly decreased?P<0.05?;4)compared with other groups,the relative abundance of rumen fiber degrading bacteria Marvinbryantia in trial group Y₅ and rumen Succinivibrio in trial group Y₂ increased?P<0.05?.The results show adding ADY could increased the rumen microbial richness and diversity,adding 5 g/d ADY through increased the relative abundance of rumen Firmicutes semi-fiber degrading Marvinbryantia,decreased the relative abundance of Proteobacteria lactic acid producing bacteria Succinivibrionacea_UCG-001 to affect ruminal fermentation and production performance of lactating Holstein dairy cows.In conclusion,adding 2 g/d active dry yeast in TMR had a slight influence on dairy cows.While adding 5 g/d could promoted the nutrients digestibility and increased the rumen propionate,the ration of acetate and propionate significantly decreased,the dry matter intake and milk yield significantly increased,which had an considerable economic benefit.Meanwhile,The changes of active dry yeast on ruminal fermentation and production performance of dairy cow are associated with rumen bacterial community.