| Corn,forage sorghum,napier and sudan grass are cultivated in tropical and subtropical areas of the world in autumn and summer and are usually preserved as silage for livestock feeding and biofuel production.Epiphytic lactic acid bacteria(LAB)on the surfaces of standing crops as well as during natural ensiling perform a vital role in silage acidification by conversion of water-soluble carbohydrates(WSC)into organic acids resulting in pH decline and inhibition of undesirable microorganisms.The number and species of epiphytic LAB are generally variable among different crops,even under the same growing conditions.Previous studies reported higher fermentation efficacy of epiphytic LAB compared to commercial LAB inoculants.The fermented juice of epiphytic LAB comprises of multiplied native LAB of plants.Selective harnessing and transferring of epiphytic LAB from healthy crops could induce positive fermentation attributes observed on the donor crop to the receipt crop.However,information concerning the direct transfer of epiphytic microbiota between different tropical forages as well as the resulting microbial and fermentation transformation of recipient forage is limited.The present study aimed to evaluate the effects of epiphytic microbiota from tropical forages on the fermentation quality and microbial community dynamics of silage.1.Evaluation of chemical composition and epiphytic microbial community of wholecrop corn,napier grass,sudan grass and forage sorghumThe present study aimed to evaluate the chemical composition and epiphytic microbial community of the four tropical forages,whole-crop corn,napier grass,sudan grass and forage sorghum.Napier grass,sudan grass,forage sorghum and whole-crop corn were harvested and were chopped into 2-3 cm of length to determine their chemical composition and epiphytic microbial community.Epiphytic microbiota was extracted from the plant surfaces of napier grass(NAP),sudan grass(SUD),whole-crop corn(WCC)and forage sorghum(FS)to evaluate their composition and abundance.The forage sorghum and whole-crop corn have significantly higher(p<0.05)dry matter(DM)and water soluble carbohydrates(WSC)contents compared to napier and sudan grasses.The buffering capacity of whole-crop corn was lower(p<0.05)among the four forages.The phylum Proteobacteria was highly dominant in all of the four epiphytic microbiota source.In the present study,Enterobacter were the dominant genera in WCC(32.8%)and FS(35.9%)microbiota,while Acinetobacter were the dominant genera in NAP(37.4%)and SUD(25.6%)microbiota.Among the LAB genera,Lactococcus was the most dominant genera in all of the four forage epiphytic microbiota,however their proportion varies among the different forage type.The higher DM and WSC contents were strongly positively correlated with Rosenbergiella and Enterobacter genera.The genera of Acinetobacter,Paenibacillus and Brucella had higher positive correlations with pH,neutral detergent fiber(NDF),acid detergent fiber(ADF)and crude protein(CP)contents.It is concluded that different tropical forages vary in their chemical composition and inhabit different proportion and types of epiphytic microorganisms.2.The feasibility and effects of exogenous epiphytic microbiota on the fermentation quality and microbial community dynamics of whole-crop cornThis study analyzed the feasibility and effects of exogenous epiphytic microbiota on the fermentation quality and microbial community dynamics of whole-crop corn.Gamma irradiated chopped whole-crop corn was ensiled with distilled water(STR),extracted microbiota of whole-crop corn(WCC),napier grass(NAP),forage sorghum(FS)and sudan grass(SUD),respectively.Inoculation of WCC to whole-crop corn significantly increased lactic acid(LA)concentrations and decreased the pH during early ensiling.The WCC inoculated silage have significantly higher LA accumulation during 7 days of ensiling compared to the rest of the treatments;however.the concentration of LA decreased with advance ensiling.The FS inoculated silage maintained lower pH throughout the ensiling and have higher(P<0.05)LA content in relation to other treatments during the terminal stage of ensiling.Inoculation with NAP caused higher pH,acetic acid(AA)contents and ammoniaN with higher dry matter losses during ensiling,followed by SUD silage.The NAP inoculated silage has the lowest ratio of LA/AA throughout ensiling in relation to other inoculated silages.After 3 days of ensiling WCC inoculated silage were dominated by Lactobacillus while FS silage was dominated by Lactococcus genera.The NAP and SUD treated silages were dominated by genera of Weissella during 3 days of ensiling.Terminal silages with FS were dominated by Lactobacillus,Lactococcus,Leuconostic,and Weissella,while NAP silage was dominated by genera of Acinetobacter,Sphingobium and Lactobacillus.The genera of Lactobacillus,Sphingobium,Acinetobacter and Acetobacter dominated SUD inoculated terminal silage.The prominent bacterial genera in WCC inoculated final silage were Lactobacillus,Acinetobacter,Sphingobium and Acetobacter respectively.The study demonstrated that forage sorghum microbiota transplantation positively influenced the microbial community and fermentation quality of whole-crop corn silage compared to other forage microbiota.3.Effect of epiphytic microbiota inoculation on the fermentation quality and microbial community dynamics during the ensiling of sterile napier grassThe study aimed to evaluate the effect of epiphytic microbiota inoculation on the fermentation quality and microbial community during the ensiling of napier grass.Gamma irradiated chopped napier grass was ensiled with distilled water(STR),extracted microbiota of napier grass(NAP),sudan grass(SUD),whole-crop corn(WCC)and forage sorghum(FS),respectively.Inoculating napier grass with WCC significantly increased lactic acid(LA)concentrations during the initial ensiling period followed by a decline after 30 days.Relative to other silages(except STR)inoculation with NAP resulted in lower LA and greater pH,acetic acid(AA),ammonia-N and dry matter(DM)losses.Silage inoculated with FS and SUD maintained lower pH as well as higher(P<0.05)LA concentrations after 60 days of ensiling.Inoculation with NAP caused a significantly lower ratio of LA/AA throughout the ensiling as compared to the rest of the microbiota treatments.In comparison to other treatments the yeast numbers were lower and below the limit of detection(<102 cfu/g FW)in the terminal NAP silage.During day 3 of ensiling.WCC,NAP and SUD inoculated silage were dominated by bacterial genera of Lactobacillus while Lactococcus dominated the FS silage.Final silages of the FS and SUD were dominated by Lactobacillus and Lactococcus,while NAP inoculated silage have predominant bacterial genera of Lactobacillus and Enterobacter.The terminal WCC silage were dominated by genera of Lactobacillus and Acetobacter.The study revealed that inoculation of epiphytic microbiota of forage sorghum and sudan grass positively influenced the microbial community and fermentability of napier grass silage.4.Dynamics of microbial community and fermentation quality during ensiling of sterile sudan grass inoculated with different epiphytic microbiotaTo investigate the dynamics of epiphytic microbiota of forages and their effects on fermentation of sudan grass was performed.Gamma irradiated chopped sudan grass material were ensiled with distilled water(STR),extracted microbiota of sudan grass(SUD),forage sorghum(FS),napier grass(NAP)and whole-crop corn(WCC).The FS inoculated silage had significantly low lactic acid(LA)concentrations and high pH value during early ensiling.However,the LA concentration gradually increased with the progression of ensiling and was the highest(P<0.05)after 60 days of ensiling in relation to other treatments.Inoculation of sudan grass with NAP resulted in lower LA and higher acetic acid(AA)concentrations,pH,ammonia-N and dry matter losses during the terminal ensiling period,followed by SUD silages.Silage inoculated with WCC microbiota significantly increased LA production and pH decline during early ensiling periods and had high LA concentration and pH than NAP and SUD silages during 60 days of ensiling.The NAP inoculated silage resulted in lower(P<0.05)LA/AA ratio and ethanol concentration during the ensiling.The early fermentation stage of SUD silage was dominated by the genus of Pediococcus.The genera of Lactobacillus were predominant in WCC and NAP inoculated silages during three days of ensiling,while Weissella dominated initial microbial community of FS silage.The terminal silages of NAP were dominated by Enterobacter and Rosenbergiella,while Enterobacter and Lactobacillus were the prominent bacterial community of the terminal SUD inoculated silages.The final silage of FS inoculated microbiota was dominated by Lactobacillus,Weissella and Pediococcus.The bacterial genera of Lactobacillus and Acetobacter were dominant in terminal WCC silage.Thus forage epiphytic microbiota transplantation can be a potential practice to enhance silage fermentation quality of less readily fermentable forages.5.Fermentation quality and microbial community dynamics of forage sorghum silage inoculated with epiphytic microbiotaThis study aimed to evaluate the effects of epiphytic microbiota inoculation on the fermentation quality and microbial community dynamics of sterilized forage sorghum silage.Gamma irradiated chopped forage sorghum material were ensiled with distilled water(STR),extracted microbiota of sudan grass(SUD),forage sorghum(FS),napier grass(NAP)and whole-crop corn(WCC).Inoculation of WCC to forage sorghum resulted in higher(P<0.05)pH and lower(P<0.05)LA and AA concentration compared to other treatments,during 3 days of ensiling.The NAP and SUD inoculated silages have statistically similar pH,LA and AA contents during 3 and 60 days of ensiling.After 60 days of ensiling the FS and WCC inoculated silage have lower(P<0.05)pH and higher(P<0.05)LA concentration compared to NAP and SUD silages.The NAP and SUD inoculated silages had higher(P<0.05)concentration of AA and lower(P<0.05)DM contents during terminal ensiling compared to the rest of the microbiota treatments.The genera of Weissella and Lactobacillus dominated FS silage during 3 days of ensiling,while NAP and SUD inoculated silages dominated by Weissella,followed by Lactococcus genera.Bacterial genera of Lactococcus were largely dominated in WCC silages during 3 days of ensiling.The genera of Lactobacillus were predominant in all inoculated silages,followed by Lactococcus genera after 60 days of ensiling.In summary,this study showed that the four inoculated microbiota declined the silage pH and dominated by LAB genera.However,the NAP and SUD inoculated silages resulted in comparatively higher acetic acid contents which could have a positive effect on the aerobic stability of forage sorghum silage.Finally,we concluded that forage dry matter and water soluble carbohydrate contents have a significant influence on the colonization of epiphytic microorganisms.Inoculation of napier grass microbiota(NAP)caused heterofermentation during the ensiling of the four crops.Furthermore,it has the lowest LA concentrations as well as the highest ammonia-N contents in whole-crop corn,napier and sudan grass silages compared to other treatments of the corresponding crop.On the other hand,the inoculation of sudan grass microbiota(SUD)to napier grass resulted in higher LA,lower pH compared to NAP and WCC inoculated napier grass silages.In addition to that,the application of WCC and FS microbiota resulted in a homolactic fermentation pattern in the silages of the four forages.The WCC and FS inoculated silages of the four crops resulted in terminal silages with lower pH values and highest LA concentrations than the NAP and SUD inoculated silages.Relative to WCC,the FS treatment of the whole-crop corn,napier and sudan grass silages resulted in significantly higher LA concentrations and a higher abundance of LAB genera. |
