Effects Of Functional Oligosaccharides From Different Sources On Rumen Fermentation And Microbial Diversity In Vitro

This experiment adopts in vitro fermentation method,Three healthy Chinese Holstein cows with permanent rumen fistula were selected as rumen fluid donors and alfalfa as fermentation substrate.Three functional oligosaccharides from different sources（soybean oligosaccharide,chitosan oligosaccharide and mannan oligosaccharide）were selected as additives.Each functional oligosaccharide was added at different levels（0,0.5%,1.5%and 3.0%）to simulate rumen fermentation of dairy cows;The experiment was conducted in batches with 3 replicates per sample in each batch;To study the effects of functional oligosaccharides from different sources on rumen gas production index,rumen fermentation and rumen bacterial flora diversity in vitro.The test results are as follows:Experiment 1:Effects of functional oligosaccharides from different sources on gas production and nutrient degradation rate of rumen fermentation in vitro.With the increase of the dosage of soybean oligosaccharide and mannan oligosaccharide,the gas production,organic matter digestibility and feed metabolic energy increased linearly（P<0.01）;The rapid gas production part（a）decreased linearly（P<0.01）or significantly（P<0.05）;The slow gas production part（b）showed a very significant（P<0.01）secondary increase.With the increase of chitosan oligosaccharide dosage,the gas production of in vitro fermentation increased first and then decreased,and the quadratic curve（P<0.01）changed.The digestibility of organic matter in vitro decreased significantly（P<0.05）;The rapid gas production part（a）increased linearly（P<0.05）;The gas production rate（c）decreased linearly（P<0.01）.Experiment 2:Study on the effect of functional oligosaccharides from different sources on rumen fermentation parameters in vitro.With the increase of the addition level of functional oligosaccharides from three different sources,the pH of in vitro fermentation broth increased significantly（P<0.05）or very significantly linearly（P<0.01）;The concentration of NH3-N decreased linearly（P<0.05）,and the concentrations of acetic acid,propionic acid and total volatile fatty acids increased linearly（P<0.05）or very significantly（P<0.01）;With the increase of soybean oligosaccharide addition level,the ratio of acetic acid and propionic in fermentation broth decreased significantly（P<0.05）;With the increase of chitosan oligosaccharide level,butyric acid increased first and then decreased in a quadratic curve（P<0.05）.Experiment 3:Study on the diversity of rumen bacterial flora in vitro by adding functional oligosaccharides from different sources.On the basis of Experiment 1 and Experiment 2,the effect of adding 3%functional oligosaccharides from different sources on the diversity of bacterial flora in rumen was studied;At the phyla level,the dominant phyla were Firmicutes,Proteobacteria and Bacteroidetes.At the genus level,the addition of 3%soybean oligosaccharide significantly increased Acinetobacter,Streptococcus and Ruminococcaceae_UCG-005（P<0.01）,significantly decreased Prevotella₁（P<0.01）,Prevotellaceae_UCG-003,Christensenellaceae_R-7_group,Kurthia and Enterococcus.The addition of 3%chitooligosaccharide significantly（P<0.01）increased Kurthia and Ruminococcaceae_UCG-005.The bacteria added with 3%mannan oligosaccharide increased significantly（P<0.01）:Streptococcus and Christensenellaceae_R-7_group,Ruminococcaceae NK4A214_group;The bacteria decreased significantly（P<0.01）:Kurthia and Enterococcus;The three functional oligosaccharides significantly（P<0.05）reduced the abundance of Escherichia-Shigella and Ruminococcus₁（P<0.01）.In conclusion,the addition of functional oligosaccharides from different sources can improve the rumen fermentation state and increase the rumen fermentation efficiency in a dose-dependent manner.The addition of 3%soybean oligosaccharide,chitosan oligosaccharide and mannan oligosaccharide under in vitro conditions increased the abundance of some fiber-degrading bacteria and starch-degrading bacteria,which was conducive to increasing the concentration of acetic acid and propionic acid in fermentation broth and improving energy utilization efficiency.The abundance of some harmful bacteria was reduced,indicating that the addition of functional oligosaccharides played a certain role in regulating rumen fermentation and flora balance.