| The aim of this study was to evaluate the effect of Hermetia illucens(H.illucens,HI)on the growth performance and intestinal barrier function of weaned pigs under the environment of enterotoxigenic Escherichia coli(ETEC)K88.In the first part: Focus on the effect of H.illucens on the growth performance and diarrhea of weaned pigs.A total of 72 weaned pigs [28±2-day-old,8.44 ± 0.04 kg body weight(BW)] were randomly assigned to three dietary treatments: basal diet(negative control,NC),basal diet supplemented with 1 445 mg zinc/kg of zinc oxide(positive control,PC),and basal diet with fishmeal replaced with H.illucens larvae meal(HI),for 28 days in the presence of ETEC K88.Average daily feed intake(ADFI),average daily gain(ADG),ratio of feed to gain(G:F),diarrhea rate,and diarrhea index were calculated at the end of the experiment.The results showed that HI and PC increased(P < 0.05)the ADG and ADFI of weaned pigs from day 1 to 14 compared with the NC.The diarrhea incidence and diarrhea index were lower(P<0.05)in the HI from day 1 to14 and 1 to 28 of the experiment compared with NC,while the diarrhea incidence and diarrhea index in the PC were lower(P<0.05)than in the NC and HI.From day 15 to28 of the experiment,the diarrhea incidence of piglets in the HI was lower(P<0.05)than those in NC,while the diarrhea incidence and diarrhea index in the PC were lower(P<0.05)than those in the NC and HI.In the second part: At the end of the experiment,one piglet was randomly selected from each pen for sampled collection to study the effect of H.illucens larvae meal on the intestinal morphology and intestinal barrier function of weaned pigs under the environment of ETEC K88.The results showed,1)The villus height of the jejunum in the HI was higher(P<0.05)than in the NC and PC,along with the crypt depth of jejunum was lower(P<0.05)than in the NC.2)The m RNA expressions of Claudin-1in the jejunum,Occludin in the ileum and zonula occluden 1(ZO-1)in the colon were increased(P<0.05)in HI compared with NC.3)HI increased(P<0.05)the number of goblet cells and mucus layer thickness in the jejunum,and increased(P<0.05)the expression of mucin-1(MUC-1)in the jejunum,MUC-1 and MUC-2 in the ileum compared with NC.4)Compared with NC and PC,HI increased(P<0.05)the m RNA expression of porcine β defensin 1(p BD1)in the jejunum,p BD1 and p BD2 in the ileum,and p BD2,proline-arginine rich 39-amino acid peptide(PR39)and protegrin 1-5(PG1-5)in the colon.Meanwhile,HI increased(P<0.05)the m RNA expression of PG1-5 in the jejunum and ileum and the content of secretory immunoglobulin(s Ig A)in the ileum compared with NC.PC increased(P<0.05)the m RNA expression of PG1-5 in the jejunum porcine myeloid antimicrobial peptides-37(PMAP-37)in the colon compared with NC.5)Compared with NC,both HI and PC decreased(P<0.05)the m RNA expression of interleukin-1β(IL-1β)in the jejunum,IL-8 in the ileum and IL-6 in the colon,and increased(P<0.05)the m RNA expression of transforming growth factor-β(TGF-β)in the ileum and IL-22 in the colon.Moreover,the m RNA expression of IL-1βwas decreased(P<0.05)in the ileum and IL-10 was increased(P<0.05)in the ileum and colon in HI compared with the NC.6)The NMDS plot showed that samples from the PC formed a distinct cluster from those of the other groups.The univariate statistical analysis indicated an increase(P<0.05)in the abundance of Alloprevotella and Lactobacillus reuteri,and a decrease(P<0.05)in the abundance of Terrisporobacter in the colonic content in the HI compared with PC and NC.Meanwhile,HI increased(P<0.05)the abundance of short-chain fatty acid-producing bacteria Ruminococcus,Agathobacter and Faecalibacterium prausnitzii,and increased(P<0.05)the content of butyric and valeric in the colonic content compared with PC.In the third part: This part aims to investigate the possible mechanisms by which H.illucens improves intestinal immune homeostasis through the regulation of histone acetylation and toll-like receptors-nuclear factor-κB/ mitogen-activated protein kinase(TLRs-NF-κB/MAPK)signaling pathways.The results showed,1)Compared with NC,the protein expressions of sirtuin 1(SIRT1)in the ileum and colon,acetylation of histone 3 lysine 27(ac H3K27)protein in the ileum,and acetylation of histone 3 lysine9(ac H3K9)and phosphorylation of histone H3 at serine s10(p H3S10)protein in the colon were increased(P<0.05)in HI,while the expressions of histone deacetylase 3(HDAC3)and HDAC7 protein were decreased(P<0.05)in the colon.Moreover,there was an increase(P<0.05)in SIRT1 protein expression in the ileum and ac H3K9 protein expression in the ileum and colon,and a decrease(P<0.05)in HDAC3 and HDAC7 protein expression in the colon of pigs in the PC compared with those of pigs in the NC.2)The m RNA expression of nucleotide-binding oligomerization domain protein 1(NOD1)in the ileum and NOD2 in the colon were greatest(P<0.05)of pigs in the NC compared with those of pigs in the NC and PC.The ratio of p-MAPK/MAPK in the ileum and the ratio of p-NF-κB/ NF-κB in the ileum and colon were lower(P<0.05)in the HI and PC compared with the NC.There was a decrease(P<0.05)in the protein expression of TLR2 in the ileum of pigs in the HI compared with those of pigs in the NC,while a decrease(P<0.05)in TLR2 protein expression in the colon in HI and PC compared with NC.In conclusion,replacement of 3% fishmeal with H.illucens larvae meal improved the growth performance of weaned pigs in the first 2 weeks after weaning,reduced the incidence of diarrhea after weaning,and improved intestinal barrier function under the environment of ETEC K88.Moreover,H.illucens larvae meal improved intestinal immune homeostasis by promoting histone acetylation and inhibiting the activation of the TLRs-NF-κB/MAPK signaling pathway in weaned pigs. |
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