| The key microorganisms in the rumen of ruminants are directly related to the host’s growth,development and immune status.However,the rumen flora is complex and diverse,and the individual differences of ruminants are large,so the key microorganisms in each study are not completely consistent,and there are few studies on the mechanism of the flora regulating host growth performance.Therefore,it is necessary to search for the key microbes in the rumen that promote the growth and development of young dairy goats through bacterial flora transplantation,and to explore their mechanism of action.This paper verifies the feasibility of rumen fluid as a microbiota transplantation carrier,as well as the mechanism of changing the rumen dominant microflora and regulating host rumen fermentation and lipid metabolism.Experiment 1 Microbial transplantation in rumen fluid of dairy goats with different daily gains improves the structure and fermentation pattern of recipient sheepIn this study,5 young dairy goats with the highest average daily gain(147.4 ± 2.19 g)were selected from 110 healthy 6-month-old young dairy goats as rumen fluid donors,and those with lower daily gain(107.8 ± 3.58 g)were selected as rumen fluid donors.Twelve sheep were rumen juice receptors and were randomly divided into 2 groups with 6 sheep in each group.The control group(GC group)was orally administered 50 m L of sterile normal saline,and the experimental group(GR group)was administered with the same amount of donor sheep rumen fluid,once a day,for a 30-day experimental period.Weekly changes in body weight of dairy goats were recorded,rumen fluid and blood samples were collected,rumen fermentation parameters and blood biochemical indexes were determined,and the effect of microflora transplantation on rumen microflora was detected by 16 S r RNA sequencing technology.The results showed: 1)The rumen flora transplantation did not significantly change the average daily gain of young sheep(P > 0.05);2)The ratio of valeric acid in the rumen fluid of the experimental group was significantly increased(P < 0.05),and the ratio of acetate and isovaleric acid was significantly decreased(P < 0.05),the proportion of propionic acid had an increasing trend(0.05 < P < 0.10),and the ethylene-propylene ratio had a decreasing trend(0.05 < P < 0.10);3)There were significant differences in the rumen flora structure of young sheep between the two groups(P < 0.05),while the flora composition and abundance were not significantly different(P > 0.05).Giving donor sheep rumen fluid can significantly reduce the relative abundance of bacteria(Prevotella 1,Prevotellaceae UCG-003)that were significantly negatively correlated with average daily gain(P < 0.05),and significantly increased the bacteria that were positively correlated with average daily gain(P < 0.05).(Candidatus Saccharimonas,Ruminococcus 2,Ruminococcus gauvreauii group)(P < 0.05),but Streptococcus,Succinivibrionaceae UCG-001 were not significantly different(P > 0.05).4)In the experimental group,plasma total cholesterol,low-density cholesterol and high-density cholesterol were significantly increased(P < 0.05),but triglyceride and plasma glucose had no significant effect(P > 0.05).The results of this experiment show that rumen juice can be used as a carrier for bacterial flora transplantation to change the structure of the recipient flora,increase the bacterial abundance that is positively correlated with average daily gain,reduce acetic acid fermentation,and change in the direction of propionic acid fermentation.Experiment 2 Dairy goat key rumen microbes colonize rats and promote colonic fiber fermentationIn experiment 1,the abundance of bacteria positively correlated with average daily gain increased significantly,but the average daily gain of dairy goats in the GR group did not change significantly.In order to further observe whether the changes in the structure of the alimentary canal flora affect the growth performance of the recipient animals and the possible mechanism of action,the following experiments were carried out using mature model animals-SD rats.Ten dairy goats with the highest average daily gain and the lowest average daily gain at 6 months were selected,rumen fluid was collected and then suspended and centrifuged to obtain rumen fluid microorganisms,and 20% glycerol was frozen for future use.Twenty 3-week-old female SD rats(50 ± 10 g)were randomly divided into two groups.After pre-fed for 3 d,they were continuously fed with antibiotics for 7 d,and then entered the positive test period(21 d).The two groups of rats were fed with the rumen flora of low-dairy goats(RS group)and the rumen flora of high-dairy goats(RF group),1 m L per day,for 14 days and every other day.Irrigation once.Feed intake and weekly body weight changes were recorded,the content of short-chain fatty acids in the colonic chyme was detected,and the effect of bacterial transplantation on the colonic microflora was detected by16 S r RNA sequencing technology.The test results showed: 1)There was no significant difference in the average daily weight gain between the two groups of rats after feeding for21 days(P > 0.05),and the average daily feed intake of the RF group showed an increasing trend compared with the RS group(P = 0.085);2)The concentrations of propionic acid,butyric acid and total volatile acid in colonic fermentation products of rats in the RF group were significantly increased(P < 0.05),and the concentration of acetic acid had a tendency to increase(P = 0.094);3)The RF group and the RS group were rich in flora There was no significant difference in degree and diversity(P > 0.05),but there was a significant difference in the bacterial community structure at the genus level(P < 0.05).The RF group was positively correlated with the average daily weight gain(Bifidobacterium,Christensenellaceae R-7 group).The relative abundance of Candidatus Saccharimonas increased significantly(P < 0.05),the relative abundance of Candidatus Saccharimonas had a trend of increase(P = 0.066),and the relative abundance of bacteria(Ruminococcaceae)that was significantly negatively correlated with average daily gain had a trend of decrease(P = 0.095).In conclusion,the rumen flora of young sheep with different daily weight gain significantly changed the colonic flora structure of SD rats.The key microorganisms in the rumen successfully colonized SD rats and promoted the fermentation of propionic acid in the colon.It is feasible to use the rat model for mechanism verification.Experiment 3 Effects of rumen microbial fermentation products on lipid metabolism in SD ratsOn the basis of Experiment 2,the regulation mechanism of key rumen microorganisms on the growth and development of dairy goats was revealed by analyzing blood biochemistry,liver lipid metabolism-related gene expression,and adipose tissue HE staining in SD rats.The results showed: 1)The content of triglyceride in the plasma of the rats in the RF group was increased(P < 0.05),and there was no significant difference in the content of triglyceride and total cholesterol in the liver(P > 0.05);2)The expression of LXRα in the liver of the rats in the RF group Significantly increased(P < 0.05),while the expressions of fatty acid β-oxidation genes PPAR-α and CPT-1α had no significant changes(P > 0.05);the expression of fatty acid de novo synthesis gene SCD-1 was significantly increased(P < 0.05),ACC,FAS expression had no significant change(P > 0.05);3)Transplantation of high daily gain dairy goat rumen microbes promotes white adipose tissue deposition in rats.The results show that rumen microorganisms and their metabolites affect lipid deposition in the body by regulating the de novo synthesis of fatty acids in the liver.In conclusion,rumen juice microbial transplantation can improve the host’s digestive tract microflora,promote rumen propionic acid fermentation and liver fatty acid de novo synthesis,improve energy utilization efficiency,affect lipid deposition in the body,and regulate the growth and development of young dairy goats. |
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