Studies On Effects Of Sorghum Tannin Extract On Sorghum Nutrient Degradation Efficiency And Application Of Polyethylene Glycol Complexing Tannin In Vitro

The development and application of sorghum as animal feed sources is of urgent practical significance.In this study,an in vitro method was used to simulate the digestive process of the pig intestines digestive enzyme（pepsin and pepsin–pancreatin）and gut microbes.Effects of the sorghum tannin extract on the nutrient degradation efficiency and the application effect of polyethylene glycol（PEG）complexing tannin were studied.First,different gradients（0,0.25,1,3,5%）of sorghum tannin extracts were added into low tannin sorghum to explore the lowest dose of negative effects on nutrient enzymatic hydrolysis efficiency（Experiment 1）.On this dose basis,the effects of sorghum tannin extract on nutrient enzymatic hydrolysis efficiency and microbial fermentation parameters were investigated（Experiment 2）.Secondly,different gradients of PEG（0,0.25…..）were added to high tannin sorghum and the dose effects of PEG complexing sorghum tannin on nutrient enzymatic hydrolysis efficiency was investigated（Experiment 3）.On this dose basis,the effects of PEG on nutrient enzymatic hydrolysis efficiency and microbial fermentation parameters by complexing sorghum tannin were investigated（Experiment 4）.1.Effects of tannin extract on in vitro enzymatic hydrolysis efficiency and microbial fermentation parameters of sorghum nutrientsExperiment 1:Sorghum tannin extract（tannin content 95%）was added to low tannin sorghum（tannin content 0.35%）by 0%,0.25%,0.5%,1%,3%and 5%,respectively.The results showed that in both the pepsin and pepsin–pancreatin digestion prossess,the disappearance rates of ADM,N and GE were decreased linearly with the increased proportion of sorghum tannin extract（P<0.05）.And 0,0.25%,0.5%,and 1%sorghum tannin extract had no significant difference in nutrient（ADM,N,GE）disappearance,but is significantly higher than 3%and 5%supplementation（P<0.05）.Experiment 2（Part 1）:Low tannin sorghum grain supplemented with or without sorghum tannin extract（3%）were enzymolyzed,and then the residues were fermented by microorganisms from pig cecal chyme.The results showed that sorghum tannin extract decreased the disappearance rate of ADM,GE and N by pepsin or pepsin-pancreatin degradation and microbial fermentation,and decreased the total gas production of microorganisms and the concentrations of total volatile acid,acetic acid and propionic acid in fermentation broth（P<0.05）.In addition,sorghum tannin extract decreased the relative abundance of Firmicutes,Proteobacteria,Succinovibrio,Lachnospiraceae AC2044 and NK4A136 in fermentation broth（P<0.05）.The relative abundance of Fusobacteria and Fusobacterium was increased（P<0.05）.（Part 2）:Ileal digesta of pigs fed low tannin sorghum supplemented with or without sorghum tannin extract（3%）were fermentated in vitro by cecal chyme microorganism.The results showed that sorghum tannin extract decreased the ADM,GE and N disappearance rates,total microbial gas production,and the concentrations of total volatile acid,propionic acid and ammonia-nitrogen in fermentation broth（P<0.05）.In addition,sorghum tannin extract decreased the relative abundance of Fusobacteria,Fusobacterium,Lachnospiraceae AC2044 and NK4A136 in fermentation broth（P<0.05）,and increased the relative abundance of Proteobacteria and Bacteroidetes（P<0.05）.2.Effects of PEG on in vitro enzymatic hydrolysis efficiency and microbial fermentation parameters of sorghum nutrientsExperiment 3:Polyethylene glycol（PEG:Tannin=0:1,0.5:1,1:1,2:1,5:1）was added to high tannin sorghum（tannin content 4.5%）.The results showed that the disappearance rates of ADM,N,and GE by pepsin and pepsine-pancreatin degradation were linearly increased with the increased PEG supplementation（P<0.05）,and the nutrient disappearance rates were significantly increased when the PEG:tannin was 0.5-5:1（P<0.05）.Experiment 4（Part 1）:The high tannin sorghum was enzymolyzed supplemented with or without PEG（PEG:tannin=1:1）,and the residue was fermented by microorganism from pig cecal chyme.The results showed that PEG increased the enzymatic hydrolysis（pepsin,pepsin–pancreatin）and microbial degradation efficiency of nutrients（P<0.05）,total microbial gas production（P<0.05）and the concentrations of total volatile acid,acetic acid,propionic acid and butyric acid（P<0.05）in sorghum fermentation broth.In addition,PEG increased the relative abundance of Firmicutes and Proteobacteria,Succinovibrio,Roseburia,Lachnospiraceae AC2044 and NK4A136 in fermentation broth（P<0.05）,and decreased the relative abundance of Fusobacteria and Fusobacterium in fermentation broth（P<0.05）.（Part 2）:The ileal digesta of pigs fed high tannin sorghum grain with or without PEG（Tannin:PEG=1:1）was fermentated by microorganism from pig cecal chyme.The results showed that PEG increased the disappearance rates of DM,GE and N in ileal digesta of sorghum（P<0.05）.And the total gas production of fermentation broth was increased（P<0.05）.PEG increased the concentrations of total volatile acid,propionic acid,NH₃and MCP,and decreased the p H value of fermentation broth（P<0.05）.PEG increased the relative abundance of Fusobacteria,Fusobacterium and Lachnospiraceae AC2044（P<0.05）,and decreased the relative abundance of Succinovibrio and Roseburia（P<0.05）.In conclusion,the supplemental level of sorghum tannin extract by no more than 1%had no negative effects on the efficiency of sorghum nutrient enzymatic hydrolysis in vitro.More than 3%of sorghum tannin extract significantly reduced the efficiency of sorghum nutrient enzymolysis and microbial degradation in vitro.The PEG（PEG:tannin ratio=1:1）could improve the efficiency of sorghum nutrient enzymolysis and microbial degradation,and had the potential to alleviate the anti-nutritional characteristics of sorghum tannin.