Effect Of Lactic Acid Bacteria On Alfalfa Silage Quality And In Vitro Rumen Fermentation

The purpose of this study was to investigate the effects of lactic acid bacteria(LAB)addition on alfalfa silage fermentation quality,nutritional value(based on Cornell’s net carbohydrate protein system,CNCPS)and microbial diversity,and the effects of LAB addition and addition ways on rumen microbial function.Experiment 1: Eight strains of LAB were isolated and screened from alfalfa silage with favorable fermentation quality,and identified by biochemical and 16 Sr DNA sequencing.The result were Lactobacillus coryniformis(LCO),Lactobacillus casei(LCA),Lactobacillus plantarum(LPL),Lactobacillus pentosus(LPE),Enterococcus faecium(EF),Streptococcus thermophilus(ST),Pediococcus acidilactici(PL),and Pediococcus pentosaceus(PP).Experiment 2: Alfalfa in the budding stage was selected for the ensiling,and it was wilted to a dry matter(DM)content of 350 g / kg fresh weight(FW).The experiment was set as 9 treatment groups: a control group(C)and the above-mentioned 8 kinds of LABs at 106 cfu / g FW,and the fermentation parameters,CNCPS components and microbial diversity were analyzed after ensilig of 7,15 and 60 days.The results showed that LPE and PP groups had the best fermentation quality,and compared with group C,they could significantly reduce(P<0.05)the p H and ammonia nitrogen(NH3-N)content,xylose content,and PB2 and PC components of alfalfa silage,but significantly increased(P<0.05)the content of lactic acid(LA),PA and PB3 components.The relative abundance of Lactobacillus in the LPE group was the highest,followed by Pediococcus,but the relative abundance of Pediococcus in the PP group was the highest,followed by Lactobacillus.Experiment 3: The effects of 8 different LAB addition ways(silage-added and rumen-added)on rumen fermentation parameters,in vitro dry matter digestibility(IVDMD),ruminal microbial populations and enzyme activity were studied.The results showed that LPE and PP added to silage had significantly higher 48 h in vitro gas production than their rumen-added(P<0.05);the IVDMD of the silage-added PL group was significantly higher than its rumen-added group(P<0.05).The xylanase activity of the silage-added PL group was significantly higher than that of its rumen-added(P<0.05).In addition,when each LAB was added to the rumen,the number of total bacteria,R.albus and B.fibrisolvens was significantly higher than that of silage-added(P<0.05),and the number of methanogens was lower(P<0.05).In summary,Lactobacillus pentosus and Pediococcus pentosus are effective for silage fermentation,which indirectly affects in vitro digestion by improving the fermentation quality of alfalfa silage;in addition,Pediococcus lactis is effective in improving the in vitro digestion efficiency from direct effects of Pediococcus lactis in the rumen.