Effects Of Dietary Supplementation With Compound Probiotics On Production And Intestinal Health In Aged Laying Hens

Lactobacillus acidophilus and Bacillus subtilis are of interest to the farming industry for their ability to promote growth performance,improve oxidative stress and modulate the immune response.However,different probiotic strains and combinations of multiple probiotics may perform better.The aim of this study was to evaluate the effects of dietary supplementation with Lactobacillus acidophilus and Bacillus subtilis on the performance and intestinal health of aged laying hens,in order to improve the economic efficiency of aged laying hens and promote the application of probiotics formulations in feed additives.Firstly,the effects of compound probiotics(Lactobacillus acidophilus CGMCC1.18778 and Bacillus subtilis ACCC11088)on the performance and egg quality of aged laying hens was investigated.2160 50-week-old Hy-Line brown hens were randomly divided into 3 groups with720 hens in each group: NC group(provided with basal diet),LD group(basal diet supplemented with 250 mg/kg of compound probiotics)and HD group(basal diet supplemented with 500 mg/kg of compound probiotics).The pre-breeding was lasted for 1 week and the experiments was lasted for 7 weeks.Egg production in the LD and HD groups increased by3.04% and 2.55% respectively after supplemented with compound probiotics(P>0.05);the daily feed intake of hens in the HD group was reduced by 7.47 g/d(P>0.05).In terms of egg quality,dietary supplementation with compound probiotics significantly reduced egg breakage,while no significant difference in shell strength,egg white height,Haugh units,yolk colour and egg shape index among the three groups.Secondly,the effect of dietary supplementation with compound probiotics on intestinal health in the aged laying hens was investigated.The results showed that dietary supplementation witn compound probiotics significantly increased the total antioxidant capacity of the ileum and cecum,enhanced the activity of mucosal catalase and glutathione peroxidase,and reduced the accumulation of malondialdehyde.This indicates that the mucosal antioxidant capacity was enhanced by the dietary supplementation with compound probiotics.Compared with the NC group,ileal villus integrity was improved,plasma lipopolysaccharide(LPS)levels were significantly reduced,ileal and cecum tight junction proteins(ZO-1,Occludin,Claudin-1)and β-defensins(Av BD2 and Av BD9)gene expression were significantly upregulated,the number of ileal goblet cells and mucin 2 were significantly increased,and the level of secreted immunoglobulin A(SIg A)was significantly increased in the ileum and cecum after compound probiotics supplemented.These results suggest that dietary supplementation with compound probiotics can strengthen the intestinal barrier function in aged laying hens.In addition,dietary supplementation with compound probiotics increased the levels of Ig G in the ileum and Ig M in the cecum,and down-regulated the expression of genes(TLR4,My D88,NF-κB)to inhibited the secretion of pro-inflammatory cytokines(IL-6,IL-17,TNF-α and INF-γ)in the intestinal mucosa and increased the level of anti-inflammatory cytokine IL-10 in the mucosa.The effects of dietary supplementation with compound probiotics on the composition of the cecum flora was further investigated.The results showed that dietary supplementation with compound probiotics significantly increased the alpha diversity and F/B values of the cecum flora,significantly reduced the relative abundance of Bacteroides,Shigella and Subdoligranulum,and increased the relative abundance of Lactobacillus,Veillonella,Aerococcus and Megasphaera.Finally,the effects of dietary supplementation with compound probiotics on metabolites in cecum contents was investigated by LC-MS/MS.Fifty-six metabolites significantly altered by probiotics were filtered out from cecum contents,mainly involving multiple metabolic pathways such as pantothenic acid and Co A biosynthesis,glycerophospholipid metabolism,aminyl-t RNA biosynthesis,purine metabolism,and amino acid metabolism.Correlation analyses revealed that Bacteroides,Lactobacillus,Aerococcus,Veillonella,Dehalobacterium,unclassified＿Bacteroidales and unclassified＿Clostridiaceae were significantly associated with most of the differential metabolites.In conclusion,dietary supplementation with Lactobacillus acidophilus and Bacillus subtilis complexes improved intestinal antioxidant capacity,maintained mucosal immunity and inflammatory homeostasis,regulated intestinal microbial composition and flora metabolism to improve egg production in late-phase laying hens,with the HD group showing better efficacy than the LD group.