Fermentation Characteristics And In Vitro Amino Acid Digestibility Of Alfalfa Silage Ensiled At Half Moisture Content With Different Varieties Of Lactic Acid Bacteria

This study was conducted to investigate the effects of lactic acid bacteria(LAB)addition on fermentation quality,nutritional value,bacterial diversity and in vitro amino acid digestibility of wilted alfalfa silage(50% moisture content).In this experiment,a single factor completely random design was adopted.Alfalfa was cut at the early flowering stage and dried in the field until the dry matter content was about 50%,which was used as silage material.Experiment 1: Without LAB addition as control group(C),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)treatment groups.All inoculants were applied at a rate of1.0×106 cfu/g fresh weight(FW).After 7,15 and 60 days of ensiling,the silage were sampled and determined CNCPS components,fermentation parameters and bacterial diversity.The results showed as follows: compared with C group,LCO,LCA,LPE and PL groups decreased p H and increased the content of lactic acid(LA).The p H of LPE group was significantly lower than that of the other seven LAB groups,and the content of LA was significantly higher than that of the other seven LAB groups(P<0.05).The dominant bacteria in the LPE group were Lactobacillus,followed by Pediococcus,and the dominant bacteria in the PL and PP groups were Pediococcus,followed by Lactobacillus.Compared with C group,the proportion of medium degradable protein(PB2)in LPL,LPE,EF,ST and PL groups was significantly increased(P<0.05),and the proportion of binding protein(PC)in LCO,LCA,LPL,EF,PL and PP groups was significantly decreased(P<0.05).LCO,LPL,LCA,EF and LPE groups could effectively reduce the decomposition of Met and Lys in silage by microorganisms.Experiment 2: The effects of eight LAB species inoculation on rumen fermentation parameters,enzyme activities and bacterial diversity of silage were studied by in vitro gas production method.The results showed that the NH3-N content of PL and PP groups was significantly lower than that of C group(P<0.05).The activities of β-glucosidase,pectinase and α-amylase and the proportion of Butyrivibrio fibrisolvens in ST group were increased compared with that in C group.Experiment 3: The effects of eight LAB species inoculation on amino acid digestibility of silage were studied in vitro.The results showed that the rumen degradability of Met was significantly decreased when silage inoculated with LAB(P<0.05),and the rumen degradability of Lys was significantly decreased when silage inoculated with LCA(P<0.05).Silage inoculated with LAB significantly increased the Met content of rumen nondegradable protein(P<0.05),while PL,ST and LCA inoculation significantly increased the Lys content of rumen nondegradable protein(P<0.05).ST,LCO,LCA and EF groups had significantly higher Met absorption(P<0.05),while PL and LCA groups had significantly higher Lys absorption in small intestine(P<0.05)compared with those of C group.In addition,addition of PL and LCA could significantly increase the absorption of total amino acids in small intestine(P<0.05).Summary,L.pentosaceus could significantly improve the quality of wilted alfalfa silage.L.casei and P.lactis could significantly increase the absorption of total amino acids of wilted alfalfa silage in the small intestine and provided more amino acids for ruminants.