Effects Of Age And Diarrhea On Intestinal Flora Of Boer Goats And Screening Of Intestinal Probiotics

The intestinal flora of animal plays a great role in promoting body's nutrition metabolism and growing development,improving the intestinal microenvironment and stimulating intestinal mucosal immunity.The imbalance of the intestinal flora can cause some intestinal diseases.Furthermore,it can make animal diarrhea,immune function and growth index reduced,which will bring huge economic losses to the breeding industry.As an excellent breed of meat goats,Boer goat has the characteristics of large size,fast growth,high rate of reproduction and high slaughter rate,so the scale of breeding in China is expanding continuously.However,intestinal diseases have been criticized for the development of sheep industry,especially in lambs.Because of the poor development of intestinal flora and body's low immunity,the intestinal tract is invaded by pathogenic bacteria easily,which can also cause diarrhea and other intestinal diseases.Intestinal microbes play an important role in maintaining animals' health,but there are few studies reported on the intestinal flora of Boer goats,the composition and structure of intestinal microflora are also not understood accurately.In addition,with the improvement of food safety requirements at home and abroad,the methods of treatment based on antibiotic have gradually been replaced by other methods,like Microecologic preparations.Microecologic preparations have many advantages,such as high efficiency,no residue,non-toxic effects.Recently,it has become the first choice for intestinal diseases.However,there is no specific microecological preparation for Boer goat,and we have not enough knowledge about the gut microflora.Therefore,this experiment was used to analyze the intestinal microflora structure of Boer goat by high throughput sequencing technology,and explore the changing rule of the intestinal flora under the influence by age and diarrhea.The composition,diversity,sample clustering and STAMP of the rectal samples were analyzed by high throughput sequencing.The results showed that the composition of intestinal flora was different under the influence by the age and diarrhea.The main manifestation was that the age factor had a great influence on the type of intestinal flora and the proportion of the bacteria groups,while the diarrhea factor had a great influence on the intestinal flora's composition and type of the intestinal dominant bacteria group.At the phylum level,Proteobacteria,Saccharibaacteria,Fusobacteria,Tenericutes in the adult sheep samples showed higher abundance than the lamb.Firmicutes and Actinobacteria in the diarrhea lamb samples were higher than the healthy lamb.At the family level,the species diversity of the intestinal flora in adult groups was higher than the lamb groups.In addition to Bacteroidales_S24-7_group,Succinivibrionaceae appeared in the adult sheep intestinal tract,and there were also differences between the two groups in the proportion of the bacteria groups.The changes of Rikenellaceae,Bacteroidaceae,Lachnospiraceae,Peptostreptococcacea and Fibrobacteraceae were also obvious.Although the bacterias in the gut of the lamb are gradually similar to adult sheep in their species and structure,there was still a difference in the proportion of the bacteria,which may be the reason why the lamb is infected by intestinal pathogenic bacteria more easily than adult.The difference between the healthy group and the diarrhea group was more obvious.The higher abundance in diarrhea group included Bacteroidales_s24-7_<sub>group,Lactobacillaceae,Clostridiaceae,Peptostreptococcaceae and Enterobacteriaceae.There was no significant difference in the composition of intestinal microflora between adult sheep and lamb.Compared with the healthy group,the abundance of Turicibacter_sp._H121,Bacteroides_uniformis,Bacteroides_sp.₃₁₁3,Lactobacillus_amylovorus,Escherichia_coli,Bacteroides_massiliensis and Corynebacterium_maris in the diarrhea group showed an obvious increasing phenomenon.Therefore,we concluded that diarrhea factor can cause or aggravate diarrhea by altering the structure of intestinal flora and destroying the balance between intestinal floras.In alpha diversity analysis,adult sheep intestinal flora had the highest species diversity,followed by the healthy lamb group and diarrhea group was the lowest.The analysis of beta diversity showed that the microbial community composition of intestinal tract between adult sheep and the healthy lamb had a certain similarity,and the diversity of the microbial community between the diarrhea sheep and the healthy lamb was distinct.The results of alpha diversity analysis and beta diversity analysis were coincided with the results of previous bacterial community analysis.Based on the results of high throughput sequencing analysis,the normal bacterial flora of Boer goat was isolated and identified.The 5 strains included Lactobacillus plantarum,Lactococcus lactis,Streptococcus thermophilus,Bacillus licheniformis and Bacillus spore.Then the isolated strains and Lactobacillus casei which was preserved in laboratory were screened by some experiments,including the growth curve,acid and bile salt resistant test,antibacterial test,intestinal peristalsis,and cell adsorption test.Next,the dominant strains were mixed to make a microecological preparation,and intervention test of the diarrhea rats was carried out.The results showed that the microecologic preparation could not only inhibit or reduce the damage of intestinal pathogenic bacteria to intestinal mucosa effectively,but also inhibit the proliferation of pathogenic bacteria in the intestinal tract.In this study,we conducted a preliminary study on the changes about intestinal microflora of Boer goats by high throughput sequencing technology.4 strains probiotics were isolated and screened.And related indicators?the probiotic characteristics,the prevention and treatment effects of diarrhea?were tested.These results provide some data and theoretical support for development of the diagnosis and treatment of Boer goat intestinal diseases,as well as the development of intestinal microecological preparations.