Effects Of Yeast Culture On Rumen Fermentation,metabolites And Rumen Microorganisms In Rations With Different NSC Compositions

Non-structural carbohydrates(NSC)include starch and sugar,which are important components of ruminant diet.The ratio of starch and sugar will affect rumen fermentation,metabolite group and rumen microorganism.Yeast culture is a kind of green and pollut-free microecological agent.The metabolites contained in it can regulate the balance of gastrointestinal microecological flora of ruminants through synergistic effect,reduce the number of harmful bacteria and increase the number of beneficial bacteria,thus promoting rumen fermentation and improving feed conversion rate.In this study,rumen in vitro culture test was used to study the effects of yeast culture added to diets with different starch and sugar ratio levels on rumen fermentation,metabolite groups and rumen microorganisms,and to reveal the mechanism of yeast culture in diets with different NSC structure.The experiment was divided into two parts:Experiment 1: Ten small-tailed Han sheep RAMS(180-190 days old)with good body condition and similar body weight(37±2.5kg)and qualified quarantine were selected as test animals.In vitro rumen fermentation was carried out with Ankom RFS gas production device and Dairy II incubator.4*3 test design,the diet the NSC level 33,the ratio of sugar and starch respectively,so,so,if the rovers,groups of fodder were added to the dry matter basis foods 0 g/kg(c),0.1075 g/kg(n)and 0.215 g/kg(h)three levels of yeast cultures,a total of 12 groups,each group of four repeat,in vitro cultivation of 24 h after sampling,the determination of p H,ammonia nitrogen,volatile fatty acid,gas production rate,dry matter degradation rate.The results showed that the ratio of starch and sugar and the addition dosage of yeast culture had no significant effect on p H value.The dry matter degradation rate increased with the increase of carbohydrate level,and the dry matter digestibility was the highest when carbohydrate level was 12(P < 0.05).With the increase of dietary sugar level,gas production,ammonia nitrogen and volatile fatty acids showed a decreasing trend.The dry matter digestibility,gas production,ammonia nitrogen concentration and volatile fatty acids of normal yeast culture supplemental dose group(0.1075 g /kg,DM)were higher than those of the other two groups(P < 0.05).Experiment 2: rumen metabolite groups and rumen microbiome of two groups with large difference in sugar and starch ratio(sugar and starch ratio was 6:27 in group A and 12:21 in group D)were determined.Results show that the rumen metabolites metabolic pathways are involved in carbohydrate metabolism,metabolism of cofactors and vitamins,amino acid metabolism,metabolic terpenoids and ketones and other amino acid metabolism,energy metabolism,chitosan biosynthesis and metabolism,lipid metabolism and other secondary metabolites biosynthesis,nucleotide metabolism,biodegradation and metabolism,etc.In the experimental group without yeast culture,the dietary differences between groups A and D were D-alose,lactic acid and hexadecanoic acid,which were involved in carbohydrate metabolism and lipid metabolism,indicating that different proportions of starch and sugar in the diet mainly affected carbohydrate metabolism and lipid metabolism.In the normal dose of yeast cultures add YC(0.1075 g/kg,DM)in the experimental group,two groups A and D diet differences metabolites of lactic acid,glycerin(glycerol),benzene acetic acid,2-methyl butyric acid,hexadecanoic acid,caproic acid and valeric acid,involved in the metabolic pathways of carbohydrate metabolism,amino acid metabolism,lipid metabolism,digestive system.The addition of yeast culture in different NSC structure diets had certain influence on rumen microbial composition.The Chao index and Shannon index of diet in group D tended to be higher than that in group A,and the Chao index of diet in group D with normal yeast culture supplemental level(0.1075 g /kg,DM)tended to be higher than that in other groups,indicating that rumen microbial diversity was the highest in diet and yeast culture with normal supplemental level in group D with low glucose and high starch.The number of Bacteroidetes in the high carbohydrate and low starch diet tended to be higher than that in the low carbohydrate and high starch group,and the supplemental level of yeast culture in normal dose(0.1075 g /kg,DM)was lower than that in the other supplemental dose groups(P <0.05).The number of RC9 in the high carbohydrate and low starch diet tended to be higher than that in the low carbohydrate and high starch diet.Although there were differences in other bacteria genera among the experimental groups,the differences were not significant.Conclusion:Different NSC structure diets and yeast culture supplemental levels had different effects on rumen fermentation,metabolite group and rumen microorganism.Moreover,there was significant interaction between NSC structure and YC supplementation on rumen function.The supplementation of yeast culture(0.1075 g /kg,DM)in the high carbohydrate and low starch diet had the greatest effect on in vitro rumen fermentation,rumen metabolite group and rumen microorganism.The results of this study indicate that the application of YC in NSC diet should be differentiated and scientifically added according to the structure of NSC.