| With the rapid development of China’s economy,people have a higher demand for healthy food,especially livestock and poultry products.The purpose of livestock and poultry breeding is to provide healthy and nutritious meat for human beings.Amongst highly consumed meat,chicken is regarded as a healthy meat with low fat content,high protein percentage and lean meat content.At present,the development of poultry industry in China shows a trend of rapid growth,the important goal of the whole industry is the production of high quality poultry products which are healthy and harmless to consumers.So far,enteritis is still one of the most important diseases that threatening early life development in young chicken by causing poultry diarrhea and highly mortality,eventually leading to huge economic loss.At present,antibiotics are used to prevent and treat enteritis in farms,but the abuse of antibiotics leads to drug resistance and even mutation of pathogenic bacteria.In addition,the Ministry of Agriculture and Rural Affairs of the People’s Republic of China issued a notice banning the use of antibiotics in animal feed,which may be harmful to humans.As an alternative treatment choice for antibiotics,probiotics can regulate the balance of intestinal flora,enhance intestinal mucosal barrier,improve immunity of livestock and poultry,and resist pathogenic bacteria and virus infection.Traditional probiotics,such as Lactobacillus and Bifidobacterium,have strict requirements on environmental conditions.They cannot survive in high temperature environment and gastric acid,and are difficult to exert their functions after entering the intestinal tract through feed.Different from other probiotics,Bacillus coagulans has strong heat resistance and gastric acid resistance,and its spores can survive in high temperature and continue to grow and reproduce in the intestines after being activated by gastric acid,making it a good choice for feed additives,however,the screening of fine Bacillus coagulans and its role in regulating intestinal health of poultry is still unclear at present.Therefore,the purpose of this study was to explore the mechanism of Bacillus coagulans as feed additive in broiler chicken breeding in order to provide warranted theoretical basis for its application in breeding practice in the future.1 Screening and identification of Bacillus coagulansAt present,the research of probiotics has been specifically focused on the level of bacterial strains,different strains of the same kind of probiotics have different biological functions.Because the Bacillus coagulans has the characteristics of good heat resistance and fast production of acid,they are widely used in production practice.However,the number of viable bacteria,heat resistance,acid production rate and germination rate of bacterial powder produced by different companies are greatly different which directly affects the performance of strains and resulting in significant difference in the effect of livestock and poultry breeding terminals,therefore,the screening of Bacillus coagulans with more significant probiotic function is very important to ensure the eco-friendly environment for breeding of livestock and poultry.In this experiment,Bacillus coagulans produced by five different companies were selected,including Company A,B,C,D and E.Firstly,the characteristics of bacterial powder were compared,such as uniformity of powder,color,odor and solubility.The results showed that the Bacillus coagulans powder produced by Company A,B and E were fine and smooth,had no pungent smell and good solubility.The Bacillus coagulants powder produced by Company C and D were rough and contains impurities,the Bacillus coagulans powder produced by Company D has pungent odor and large dust.Secondly through microscopic examination and colony morphology observation,it was found that normal Bacillus coagulans spores are rod-shaped,its top of body are intumescent and transparent appearing like a"match";typical Bacillus coagulans spore morphology was observed in the bacteria produced by A,B,C and E companies;the bacteria produced by Company D does not have the typical characteristics of Bacillus coagulans,it is in the shape of"grain of rice"with transparent middle and solid at both ends.By calculating the initial viable count,it was found that the viable count of Bacillus coagulans produced by Company A was much higher than that of other companies,as high as 359 billion/g,and the survival rate was 64.6%and 91%after 90℃water bath heating and oven heating respectively,indicating the best heat resistance.Finally,the acid production and germination rate of Bacillus coagulans spore after high temperature were tested,it was found that the average p H value of culture medium of Bacillus coagulans produced by Company A could reach 4.67 at 7 h,indicating that it could produce acid and germinate quickly in a short time.The quality of Bacillus coagulans powder produced by Company A showed excellent quality and outstanding performance,prominently its ability to resist gastric acid and bile salts challenge and also its inhibition function on the growth of intestinal pathogenic bacteria Salmonella enteritidis was tested..The results showed that the survival rate of Bacillus coagulans powder produced by Company A in disodium hydrogen phosphate-citric acid buffer with p H=3 and 0.3%pig bile salt buffer solution were as high as 78.3%and 98.0%;the average bacteriostatic diameter was up to 8.25 mm,suggesting that it has a good ability of acid and bile salt resistance,and could directly inhibit the growth of Salmonella enteritidis.According to the above results,the conclusion was drawn that the Bacillus coagulans produced by Company A had good production technology,high number of viable bacteria,good heat resistance of the spores,fast acid production speed,resistance of gastric acid and bile salt and inhibition of salmonella enteritis.Therefore,the Bacillus coagulans was selected for the subsequent feeding experiment of broilers.2 Study on enhancing the function of intestinal mucosal barrier of chicken by Bacillus coagulansAt present,the molecular regulation mechanism of Bacillus coagulans on intestinal mucosal barrier of chicken is not clear.To investigate the effect of Bacillus coagulans on intestinal mucosal barrier function in chickens,16 1-day-old white-feathered broilers were selected and divided into 2 groups with 3 replicates in each group and 8 broilers in each replicate.The blank control group was fed normally everyday,and the experimental group was fed with 10~8CFU Bacillus coagulans produced by Company A everyday,the whole process lasted for 42 days,tissue samples such as jejunum and blood were taken after ending the animal test.The results found that feeding Bacillus coagulans could significantly increase the amount of albumin(ALB)and total protein(TP)in chicken serum,showed that Bacillus coagulans could promote protein synthesis in broilers,improve the feed conversion rate and accelerate the absorption of nutrition in chicken.Futhermore,we found that feeding Bacillus coagulans could reduce the concentrations of triglyceride(TG)and low density lipoprotein(LDL)in broilers,suggesting that Bacillus coagulans could improve the cardiovascular circulatory system of broilers.Then explored the effects of feeding Bacillus coagulans on the growth and development of intestinal tissue of broilers,we found that feeding Bacillus coagulans could significantly increase villus length and crypt depth,stimulate the proliferation of intestinal epithelial cells,and promote the growth and development of intestinal tissue.Further studies showed that feeding Bacillus coagulans significantly reduced the expression levels of intestinal inflammatory factors such as IL-1β,IL-6 and TNF-α,and increased the concentration of intestinal immunoglobulin A(IgA),suggesting that Bacillus coagulans could maintain the intestinal mucosal immune barrier and improve the immune performance of broilers.These results indicated that Bacillus coagulans can promote intestinal absorption of nutrients,reduce blood lipid,promote intestinal tissue development and reduce the expression of inflammatory factors,enhance intestinal mucosal barrier function and improve intestinal mucosal immunity level of broilers.3 Study on the mechanism of Bacillus coagulans against Salmonella enteritis infectionIn order to further explore the ability of Bacillus coagulans to resist Salmonella enteritidis infection,the experiment selected 1-day-old chicks,randomly divided into 4groups,each group have three replicates with 8 chicks in every replicate,including blank control group(normal feeding),Salmonella enteritidis infection group(the 3-day-old chicks were inoculated orally with 200μL 10~9CFU Salmonella enteritidis one time),Bacillus coagulans feeding group(feeding 10~8CFU Bacillus coagulans for 7 days),Bacillus coagulans repair group(feeding 10~8CFU Bacillus coagulans for 7 days,and3-day-old chicks were inoculated orally with 200μL 10~9CFU Salmonella enteritidis once).The results showed that Salmonella enteritidis infection could cause serious weight loss,shedding of intestinal villi epithelium,crypt depth reduction,and increase the levels of inflammatory cytokines like IL-10,IL-22 and IL-1β;In Bacillus coagulans feeding group,the body weight of chicks increased rapidly,the villi and crypt were healthy and well developed,and the level of IL-1βdecreased significantly compared with the blank control group;however the Bacillus coagulans repair group could effectively alleviate the weight loss and the intestinal villus injury,increase the villus height and crypt depth,and reduce the expression of inflammatory factors like IL-10,IL-22 and IL-1β,and alleviate the intestinal inflammatory infiltration.These results confirmed that Bacillus coagulans can increase body weight,promote intestinal tissue development,enhance intestinal mucosal barrier,reduce inflammatory response,and alleviate the injury caused by Salmonella enteritidis infection in chicksTherefore,this experiment confirmed that Bacillus coagulans produced by Company A has higher craft level,high number of viable bacteria,and good heat resistance,It could promote the growth and development of broilers and enhance the intestinal mucosal barrier,alleviate weight loss in chicken after Salmonella enteritidis infection,promote villi and crypt growth and reduce the inflammation factor expression level,thus alleviate intestinal damage to Salmonella enteritidis infection. |
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