青贮前后水稻秸秆非结构性碳水化合物的变化及添加剂对发酵和微生物群落结构的影响OA

Modern breeding techniques have developed rice varieties with straw rich in non-structural carbohydrates(NSC),including glucose,fructose,sucrose,and starch.However,in the high temperature and humidity conditions of southern China,such straw decomposes rapidly,leading to significant loss of available sugars.Ensiling offers a solution by converting NSC into organic acids.Nevertheless,direct ensiling of rice straw proves ineffective due to dominant Clostridium fermentation.This experiment investigated the changes in NSC of rice straw between before and after ensiling and evaluated the impacts of additives on fermentation quality,nutritive value,microbial community composition and mycotoxin load after 90 d of ensiling.Four treatments were used in this experiment:1)Control group(CK);2)Lactic acid bacteria inoculants mixed with Lactiplantibacillus plantarum and Lacticaseibacillus paracasei(HLAB);3)Calcium propionate(PACA);4)Mixture of two additives(HLAB_PACA).Three replicates per treatment.The addition rates of HLAB and PACA groups were 5×105 CFU·g-1 and 4 g·kg-1 of fresh materials,respectively.After 90 days of fermentation,all groups exhibited significant reductions in glucose,fructose,and starch(P<0.05).HLAB,PACA and HLAB_PACA groups preserved higher(P<0.05)residual glucose levels than the control group.These three additive groups also had significantly lowered pH,acetic acid,butyric acid,and ammonia nitrogen(P<0.05),with increased lactic acid production(P<0.05).Neutral detergent fiber and acid detergent fiber contents were notably decreased by additives(P<0.05).PACA and HLAB_PACA groups had increased bacterial community diversity as measured by Ace and Chao1 indices(P<0.05).The HLAB and HLAB_PACA groups comprised natural fermentative lactic acid bacteria,initially composed of 8 zero-radius operational taxonomic units(ZOTU)belonging to Ligilactobacillus,Lactiplantibacillus and Lacticaseibacillus,which evolved into a Lacticaseibacillus-dominant bacterial community(ZOTU1/ZOTU318).All additives suppressed the relative abundance of Clostridium.Fungal diversity metrics showed elevated Simpson and reduced Shannon indices(P<0.05)in HLAB_PACA group versus HLAB and PACA groups.Although the use of additives significantly increased the relative abundance of Aspergillaceae and total mould counts(P<0.05)compared to the CK,it did not cause a significant increase in mycotoxin levels,such as aflatoxin and zearalenone,which remained extremely low.Therefore,the use of lactic acid bacteria and calcium propionate additives plays an important role in improving the NSC structure,fermentation quality,and microbial community structure of rice straw silage.These data provide scientific information relevant to the efficient production of rice straw silage.