Silage Fermentation Quality Of Italian Ryegrass And Napier Grass Harvested At Various Times On Sunny Day

Italian ryegrass(Lolium multiflorum Lam.)and Napier grass(Pennisetum purpureum Sch.)is an important temperate and tropical grass,respectively.They are widely distributed throughout temperate and tropical or subtropical regions of the world and are two of China's major forage crops used either as fresh green-chop or as hay or silage for ruminants.The objective of the present study was to determine the effect of diurnal changes on chemical composition and epiphytic microorganisms and their effects on fermentation quality of Italian ryegrass and napier grass silages,this study was also analyse the decisive factors for the fermentation quality of the silages and provide a theoretical basis for the production of grass silage.1 Silage fermentation characteristics of Italian ryegrass harvested at various times on sunny dayThe aim of this experiment was to determine the effect of diurnal changes on chemical composition and epiphytic microorganisms and their effects on fermentation quality and in vitro digestibility of Italian ryegrass silages.Primary growth of Italian ryegrass(heading stage)was harvested with hand clippers at 08:00(AM),13:00(M)and 18:00 h(PM)on 27 April 2011(experiment 1),5 May 2011(experiment 2)and 5 May 2012(experiment 3).A pre-ensiled forage sample was collected and the silages were made,followed by sealing with a screw top and stored at ambient temperature for 30 days(experiment 1),1,3,5,7,14 and 30 d(experiment 2)and 1,3,5,7 and 30 d(experiment 3),respectively.Then their fermentation quality and in vitro digestibility was analyzed.Bacterial community was determined by denaturing gradient gel electrophoresis(DGGE)on pre-and post-ensiled forage samples,which were harvested on cutting day 2.The results showed that concentration of water soluble carbohydrates(WSC)in fresh forage increased,whereas concentrations of neutral detergent fiber(NDF)and acid detergent fiber(ADF)reduced from sunup to sundown.The counts of epiphytic lactic acid bacteria(LAB),aerobic bacteria,mold and yeast were higher(P<0.05)for fresh forage cut in AM as compared to those of M-and PM-cut forages.After 30 days of fermentation,the concentrations of dry matter(DM),residual WSC and lactic acid and the ratio of lactic acid to acetic acid(LA/AA)were higher(P<0.05)and the concentrations of ammonia-N(NH3-N),butyric acid and total volatile fatty acids(VFAs)and silage pH were lower(P<0.05)for silage made with PM-cut forage as compared to those made with AM-and M-cut forages.Furthermore,the in vitro dry matter digestibility(DM-D)and neutral detergent fiber digestibility(NDF-D)were higher(P<0.05)for silage made with PM-cut forage as compared to those made with AM-and M-cut forages.The M-cut silage failed to establish the jarless lactic acid bacteria fermentation.The failure of silage fermentation at the end of ensiling was due to the absence of L.plantarum,but was found Clostridium sp.In summary,the results indicated that Italian ryegrass cut in the afternoon(about at 18:00 h)of a sunny day was associated with good silage fermentation attributes and higher in vitro digestibility,and the failure of silage fermentation for Italian ryegrass cut in the noon(about at 13:00 h)due to the lower epiphytic microbial species and activity.2 Silage fermentation characteristics of napier grass harvested at various times on sunny dayThe aim of this experiment was to determine their effect of diurnal changes on chemical composition and epiphytic microorganisms and these effects on fermentation quality and in vitro digestibility of napier grass silages.The primary growth of napier grass(vegetative stage)was harvested with hand clippers at 08:00(AM),13:00(M)and 18:00 h(PM)on 30 July 2011(experiment 1),19 July 2012(experiment 2)and 25 July 2012(experiment 3).A pre-ensiled forage sample was collected and the silages was made,followed by sealing with a screw top and stored at ambient temperature for 1,3,5,7,14 and 30 days(experiment 1),1,3,5,7 and 30 d(experiment 2)and 30 d(experiment 3),respectively.Then their fermentation quality and in vitro digestibility was analyzed.Bacterial community was determined by denaturing gradient gel electrophoresis(DGGE)on pre-and post-ensiled forage samples,which were harvested on cutting day 1.The results showed that the concentration of DM and WSC in fresh forage increased,whereas concentrations of NDF and ADF reduced from sunup to sundown.The counts of epiphytic LAB and aerobic bacteria were higher(P<0.05)for fresh forage cut in AM as compared to those of M-and PM-cut forages.After 30 days of fermentation,the concentrations of DM,residual WSC and lactic acid and LA/AA were higher(P<0.05)and the concentrations of ammonia-N(NH3-N),silage pH and LAB counts were lower(P<0.05)for silage made with PM-cut forage as compared to those made with AM-and M-cut forages.Furthermore,the in vitro DM-D was higher(P<0.05)for silage made with PM-cut forage as compared to those made with AM-and M-cut forages.All the silages could establish the jarless lactic acid bacteria fermentation and L.plantarum,E.mundtii and L.lactis was the dominant bacteria on end of ensiling.In summary,the results indicated that delayed cutting of napier grass at the end of a sunny day was associated with higher WSC concentration and obtain a good silage fermentation attributes.3 Characterization and identification of lactic acid bacteria isolated from silageThe LAB was isolated from 5 and 30-d after the fermentation of silages,which were made of Italian ryegrass and napier grass harvested on 5 May 2011 and 30 July 2011,respectively.A total of 24 LAB strains were isolated average from Italian ryegrass and napier grass silages.According to phenotypic characteristics,growth at different temperatures,salt concentration and pH,carbohydrate fermentation and acid-production rate tests,these LAB strains were identified,and then choose eight of these strains for the future identified by 16S rRNA sequence.The results showed that strains R5-1,R5-2,R5-5 and R5-9 were E.faecium,L.pentosus,E.mundtii and L.mesenteroides,respectively.Strains R30-1,N30-1,N30-3 and N30-6 were L.plantarum.Strains R5-1,R5-2,R5-5,R30-1 and N30-6 were homofermentative LAB and were used for the future research.4 Lactic acid bacteria influence on silage fermentation of Italian ryegrass and napier rass harvested at various times on sunny dayThis part included two experiments.The experiment 1 was conducted to investigate the effect of E.faecium R5-1,L.pentosus R5-2,E.mundtii R5-5 and L.plantarum R30-1 on the fermentation and nutritive quality of Italian ryegrass cut at vary times on sunny day.A pre-ensiled forage sample was collected and the silages were made,followed by sealing with a screw top and stored at ambient temperature for 1,3,5,7 and 30 days.The results showed that the concentration of DM,lactic acid,WSC and LA/AA were higher(P<0.05)and the concentrations of NH3-N and silage pH were lower(P<0.05)for LAB inoculated silage as compared to uninoculated silage made with M-cut forage,and the silages inoculated with bacillis improved fermentation quality were better than coccis.The concentration of NH3-N and silage pH were lower(P<0.05)for L.plantarum R30-1 inoculated silage as compared to uninoculated silage made with AM-cut forage,but other treatments were not improve the silage quality.In PM-cut silages,L.pentosus R5-2 and L.plantarum R30-1 were improve the silage quality significantly,but E.faecium R5-1 and E,mundtii R5-5 were not.The experiment 2 was conducted to investigate the effect of E.faecium R5-1 and L.plantarum N30-6 on the fermentation and nutritive quality of napier grass cut at vary times on sunny day.A pre-ensiled forage sample was collected and the silages were made,followed by sealing with a screw top and stored at ambient temperature for 1,3,5,7 and 30 days.The results showed that L.plantarum N30-6 inoculated silage had a slightly improvement on silage quality,the concentration of acetic acid,NH3-N and silage pH were slightly lower(P>0.05),LA/AA were higher(P<0.05)as compared to uninoculated silage made of forages cut at vary times.E.faecium R5-1 inoculated silage had a slightly improvement on silage quality,the NH3-N concentration and silage pH were slightly lower(P>0.05),the WSC concentration and LA/AA were higher(P>0.05)as compared to uninoculated silage made of M-and PM-cut forages.However,E.faecium R5-1 inoculated silage made of AM-cut forage failed to improve the silage quality,this silage has slightly higher(P>0.05)NH3-N and acetic acid concentrations and lower(P>0.05)WSC concentration and LA/AA.In summary,the homofermentative LAB inoculated on silage quality was ranked in the following order:M>PM>AM.The silages inoculated with bacillis improved fermentation quality were better than coccis,which failed to improve the quality of silage made with AM-cut forage.The results indirectly indicated that the activity of epiphytic LAB was ranked in the following order:AM>PM>M.