The Probiotic Mechanism Of Bacillus Amyloliquefaciens On Laying Hens

At present,many studies have confirmed that many bacilli can improve production performance of animals,but few studies have concentrated on in-depth and systematic analyses on the mechanisms for improving production performance.It has been reported that the production performance improvement of laying hens induced by bacillus is mainly related to hormone level,immune function,anti-oxidative stress response,gut barrier function,intestinal flora structure,nutrient absorption,and secondary metabolites of probiotics.Therefore,in this study,the beneficial effects of Bacillus amyloliquefaciens(B.amyloliquefaciens)BLCC1-0238 on production performance of Hy-Line Brown laying hens was first analyzed,and then its beneficial action mechanisms were explored from 5 different levels,including physiological and biochemical indexes,gut barrier function,bacterial community in the cecum,transcriptome analysis of ileum mucosa,and functional genomics of B.amyloliquefaciens BLCC1-0238.In our study,a total of 240 Hy-Line Brown laying hens(28 weeks old)were randomly divided into four groups,and three replicates per group(n = 20 per replicate).The control group was fed a standard basal diet,and the three treatment groups were provided the basal diet supplemented with either 0.01%,0.03%,and 0.06% B.amyloliquefaciens BLCC1-0238(2�1010cfu/g),respectively.On this basis,we aimed to investigate the effects of B.amyloliquefaciens BLCC1-0238 on production performance and egg quality of laying hens,and then to analyze the possible beneficial mechanisms from 5 different levels mentioned above.This experimentation is composed of 6 parts,and the results are as follows:The first part showed that dietary supplementation with B.amyloliquefaciens BLCC1-0238 significantly increased egg production and egg mass,but no significant differences in feed intake,egg weight,and feed conversion ratio among the four groups were observed.In addition,different levels of B.amyloliquefaciens BLCC1-0238 supplementation also significantly increased egg shell strength and thickness.Therefore,supplementation of the basal chicken diet with B.amyloliquefaciens BLCC1-0238 can improve laying performance and its beneficial effect is dose-dependant.The second part showed that B.amyloliquefaciens BLCC1-0238 can significantly reduce serum adrenal cortical hormone(ACTH)levels,while increase estradiol(E2)and follicle-stimulating hormone(FSH)secretion in the treatment groups compared with the control group.In addition,supplementation with 0.03% and 0.06% B.amyloliquefaciens BLCC1-0238 can significantly increase serum glutathione S-transferase(GST)concentration,but reduce serum IL-1 and IL-6 levels.Therefore,B.amyloliquefaciens BLCC1-0238 supplementation can improve laying performance and egg quality through the reduction of stress responses,up-regulation of growth hormones,and supporting immunity in laying hens.The third part showed compared with the control,BLCC1-0238 significantly reduced the content of D-lactic acid and diamine oxidase,and crypt depth,but significantly increased the intestinal villi length,expression levels of tight junction protein and intestinal mucin,and intestinal s Ig A concentration.These results showed that Bl CC1-0238 improved the intestinal barrier function,thereby protecting the normal physiological function of the intestinal tract.Based on the experimental results of the first three parts,during the subsequent intestinal genomics and transcriptomics experiments,we selected the standard control group and the 0.06% BLCC1-0238 addition group as the research objects.The fourth part showed that B.amyloliquefaciens BLCC1-0238 can effectively increase the diversity of intestinal bacteria.At the level of phylum,the relative abundance of Firmicutes was significantly increased,while the relative abundances of Bacteroidetes and fusobacteria were reduced.At the level of genus,the relative abundances of Ruminococcaceae ucg-014,Anaerotruncus,Ruminiclostridium 9,Phascolarctobacterium and Lactobacillus were increased.In conclusion,B.amyloliquefaciens BLCC1-0238 can increase intestinal bacterial community diversity and the count of beneficial bacteria,but reduce the number of harmful bacteria.The fifth part showed that B.amyloliquefaciens BLCC1-0238 can significantly enhance the genes expression levels,which are linked with carbohydrate metabolism,amino acid metabolism,lipid digestion and intestinal absorption,and can therefore result in metabolic pathways up-regulations,which are associated with starch and sucrose metabolism,galactose metabolism,and glycine,serine and threonine metabolism.These findings suggested that B.amyloliquefaciens BLCC1-0238 could effectively improve laying performance by enhancing energy and material metabolism of laying hens.The sixth part showed that the draft genome of B.amyloliquefaciens BLCC1-0238 is approximately 3.88 Mb with 3 941 encoding sequences,and G+C content is 46.6%.A total of 8gene clusters are involved in the synthesis of non-ribosomal lipopeptides,polyketides,and bacilysin.Some genes are involved in the synthesis of cyclic lipopeptide.A gene encoding a peptidylprolyl isomerase is found,and 12 genes are related with acid tolerance and 7 genes encoding hydrolase were also found.Therefore,8 gene clusters are major contributors of B.amyloliquefaciens BLCC1-0238 to the beneficial properties.In summary,B.amyloliquefaciens BLCC1-0238 can effectively improve production performance and egg quality of laying hens.The action mechanism is associated with the improvement of host body immunity,antioxidant ability,hormone levels and gut barrier function.The increase of intestinal flora diversity and the expression enhancement of related genes with material metabolism also play an important role.In addition,multiple gene clusters of related with the synthesis of non-ribosomal lipopeptides and polyketides are beneficial to production performance of laying hens.