| Under the condition of large-scale farming in China,the low reproductive efficiency of sows is an important problem faced by modern sow production.Inadequate feed intake during lactation and impaired intestinal development in piglets are the main reasons.It is reported that there was a positive correlation between lactation intake and insulin sensitivity during perinatal period.However,pregnant women are prone to metabolic syndrome in late pregnancy,including insulin resistance and systemic low-grade inflammation.Meanwhile,obesity during late pregnancy can exacerbate metabolic disorders in pregnant women.It is worth noting that the maternal gut microbiota has also undergone significant changes during pregnancy,and the microbial changes directly lead to metabolic syndrome,but the specific mechanism is unclear.However,the changes in gut microbiota and metabolism of sows during the whole breeding cycle have not been reported.Moreover,whether and how microbial changes affect metabolic status of sows are also worth further study.In addition,the colonization pattern of gut microbiota of newborn individuals has been reported to affect intestinal barrier structure and the maturation of immune system.The bacteria in the gut and milk of sows are an important source of gut microbiota of newborn piglets.Therefore,regulating the composition of intestinal and milk microbiota of sows may be an effective means to improve the intestinal development of piglets.Previous studies in our laboratory have found that dietary fiber during pregnancy can increase the abundance of butyrate-producing bacteria and improve perinatal insulin sensitivity in sows.However,the mechanism between them has not been elucidated.Moreover,whether dietary fiber during pregnancy affects the composition of the gut and milk microbiota of sows,thereby improving growth performance and intestinal function of piglet is also worth further study.Therefore,we first attempted to elucidate the role of gut microbiota in the changes of metabolic status of sows during perinatal period.Subsequently,taking “gut microbiota” as the target,we tried to reveal the effect and mechanism of soluble fiber supplementation in pregnancy diet on improving perinatal metabolic status of sows and growth and intestinal development of newborn piglets.The main contents and results are as follows: Part I Effect of obesity during late pregnancy on perinatal metabolic syndrome of sows and growth and development of pigletsThis study investigated the effects of obesity in late pregnancy on reproductive performance,perinatal metabolism in sows,and intestinal health and immune system in piglets.Sixty sows were selected and divided into two groups according to their backfat thickness at 109 days of pregnancy,namely normal backfat group(=17 mm)and overweight backfat group(?21 mm).The litter performance of sows and growth performance of piglets were recorded and measured.Feces and blood samples of sows were collected on the 109 days of pregnancy and 3 days of lactation to determine the levels of lipocalin-2 in feces and blood glucose,insulin,zonulin,inflammatory factors and oxidative stress markers before feeding.On the 14 days of lactation,the feces and blood samples of piglets were collected to determine the levels of lipocalin-2,?-defensin-2,secretory IgA,inflammatory factors,plasma zonulin and IgM.The main results are as follows:1.Compared with normal backfat group,the number of live piglets and litter weight of piglets in overweight backfat group decreased(P < 0.05).It indicated that obesity in sows during late pregnancy reduced litter performance.There was no significant difference in average body weight and average daily gain(ADG)of piglets during the whole lactation period(P > 0.05).2.Compared with normal backfat group,the perinatal glucose concentration,homestasis model assessment-insulin resistance(HOMA-IR)value,and plasma IL-6,TNF-? and TBARS levels of sows in overweight backfat group increased(P < 0.05).It suggested that obesity in late pregnancy aggravated the perinatal metabolic syndrome in sows.Moreover,the fecal TNF-? levels of piglets in overweight backfat group increased,while fecal IL-10 levels and plasma IgM levels decreased(P < 0.05).This suggested that obesity in sows during late pregnancy may aggravate intestinal inflammation in offspring piglets.Part II Metabolic syndrome during perinatal period in sows and the link with gut microbiota and metabolitesTwelve sows with consistent genetic background and good health were selected.Fresh feces and blood samples were collected on days 30(G30)and 109(G109)of gestation and days 3(L3)and 14(L14)of lactation.Several metabolic biomarkers related to gut health were measured.The composition of fecal microbiota and short-chain fatty acids(SCFAs)was determined by 16 S rRNA sequencing and gas chromatography,respectively.On G30,G109,and L3,three meal tests were conducted to evaluate the changes of blood glucose after mealing.The main results are as follows:1.The plasma glucose levels of L3 were higher than that of G30 and G109 between 60 min to 240 min after meal(P < 0.05).Furthermore,the area under the curve of plasma glucose of L3 was higher than that of G30 and G109(P < 0.05).In addition,The plasma IL-6 levels in G109 and L3 were higher than those in G30 and L14(P < 0.05).The results indicated that sows showed obvious metabolic syndrome during the perinatal period,especially in early lactation.2.16 S rRNA sequencing showed that Firmicutes and Bacteroidetes were the most dominated phyla,followed by Spirochaetes and Proteobacteria.The relative abundance of Proteobacteria and Fusobacteria was the highest in L3(P < 0.05).At the genus level,the relative abundances of Bacteroides,Escherichia Shigella and Fusobacterium in L3 were the highest,while Oscillospira was the lowest(P < 0.05).LEfSe analysis showed that L3 mainly enriched Fusobacterium,Enterobacteriaceae,and Escherichia Shigella.Moreover,the Chao 1 and Shannon index in L3 were the lowest(P < 0.05).Principal coordinate analysis(PCoA)revealed that the gut microbiota were less dispersed in G30 and L14 but obvious segregation in G109 and L3.Gas chromatographic analysis showed that the fecal butyrate levels of L3 was lower than the other three stages(P < 0.05).The above results indicate that the gut microbiota composition,structure,and metabolites of sows is profoundly altered during pregnancy and lactation.3.The highest plasma endotoxin levels was found in L3(P < 0.05).The levels of fecal lipocalin-2,IL-6 and TNF-a were significantly higher but the levels of IL-10 were lower in G109 and L3 than those in G30 and L14(P < 0.05).Fecal endotoxin levels increased from G30 to L3 and then decreased in L14(P < 0.05).The spearman correlation analysis showed that Fusobacterium was positively correlated with plasma zonulin and fecal endotoxin but negatively correlated with fecal IL-10(P < 0.05).Part III The role and mechanism of dietary fiber regulating gut microbiota of sows to improve perinatal metabolic syndromeThis study aimed to investigate whether dietary fiber in pregnancy reduce gut permeability and plasma endotoxin levels by regulating gut microbiota of sows,thereby improving the metabolic status of sows.56 multiparous sows were selected and divided into two groups,the control(CON)and 2% dietary fiber(SF)groups.The content of other nutrients in the two diets were the same except soluble fiber.Fresh feces and fasting blood samples were collected on days 30(G30)and 109(G109)of gestation and days 3(L3)and 14(L14)of lactation.The changes of metabolic status,gut microbiota,gut permeability and gut inflammation were analysed.The main results are as follows:1.From four stages,the HOMA-IR values and the plasma levels of high sensitivity C-reactive protein(hs-CRP)in G109 and L3 were higher than those in G30 and L14,while the addition of SF decreased the HOMA-IR values and the plasma hs-CRP concentrations(P < 0.05).This indicated that dietary fiber supplementation during pregnancy improved perinatal insulin sensitivity and systemic inflammation in sows.2.16 S rRNA sequencing showed that dietary fiber during pregnancy increased the relative abundances of families Lachnospiraceae and Ruminococcaceae(P < 0.05).Moreover,the genus Oscillospira was increased when pregnancy diet was supplemented with SF(P < 0.01).In addition,the fecal and plasma levels of butyrate in SF-fed sows were higher than those in CON-fed sow(P < 0.05).These results suggested that dietary fiber supplementation during pregnancy promoted the enrichment of butyrate-producing bacteria in sow intestine and increased the yield of intestinal butyrate.3.The plasma zonulin and fecal lipocalin-2,IL-6 and TNF-a levels were remarkably raised in G109 and L3 when compared with those in G30 and L14,while dietary SF reduced the elevation of plasma zonulin and and fecal lipocalin-2,IL-6 and TNF-a.In addition,the spearman correlation analysis showed that Lachnospiraceae was negatively correlated with HOMA-IR values and plasma hs-CRP but positively correlated with HOMA-IS.Furthermore,Oscillospira was negatively correlated with plasma zonulin and fecal lipocalin-2(P < 0.05).These results suggest that dietary fiber supplementation during pregnancy may reduce intestinal permeability and plasma endotoxin levels by regulating gut microbiota,and ultimately improve perinatal metabolic syndrome of sows.Part IV Regulatory effect of dietary fiber during pregnancy on milk composition and milk microbiota of sows to improve perinatal metabolic syndromeThis study investigated the changes of milk microbiota of multiparous Landrace sows during lactation.The work also aimed to assess the regulatory effect of dietary fiber during pregnancy on milk composition and milk microbiota of sows.The experimental samples of this study are from the part III.At days 0(day of delivery),7,14 and 21 of lactation,10 sows in each treatment group were selected to collect colostrum and normal milk aseptically.The nutritional compositions of milk was analysed by infrared analyzer of milk.The milk microbiota was determined by 16 S rRNA sequencing.The main results are as follows:1.Compared with colostrum,the proportion of milk protein in milk decreased at days 7,14,and 21 of lactation,while the proportion of lactose increased(P < 0.01).Dietary fiber had no significant effect on milk protein,lactose and milk fat(P > 0.05).2.The 16 S rRNA sequencing showed that Firmicutes and Proteobacteria were the first two dominant bacteria and Moraxella and Streptococcus were the first two dominant species of milk in sows.Compared with colostrum,the ? diversity index(Chao 1 and Shannon index)of milk microbiota on days 7,14,and 21 of lactation increased,while the relative abundance of Lactobacillus,Oscillospira,Ruminococcus,Coprococcus,Dorea,Eubacterium,and Faecalibacterium increased(P < 0.01);The dietary fiber during pregnancy increased the relative abundance of Lactobacillus,Oscillospira,Ruminococcus,Coprococcus and Eubacterium in milk compared with the control group(P < 0.05).This indicated that the composition and structure of microbiota in sow milk at different lactation stages were significantly different,and the composition of microbiota in milk was changed by adding dietary fiber to the gestational diet.Part V Effects of dietary fiber during pregnancy on gut microbiota of piglets to enhance intestinal barrier and immune functionThis study evaluated dietary fiber during pregnancy on growth performance,gut microbiota and immune function of suckling piglets.Twenty-four multiparous sows were randomly divided into two groups.The control group(CON)and 2% functional fiber combination(SF)diets were fed during pregnancy,respectively.The main results are as follows:1.The final body weight(BW),the average daily gain(ADG)during week 3 and the whole suckling period was higher but the diarrhea rates and diarrhea index during the whole suckling period were lower in SF suckling piglets when compared with those in CON piglets(P < 0.05).This indicated that dietary fiber supplementation during pregnancy increased the growth rate and disease resistance of suckling piglets,and alleviated the occurrence of diarrhea during lactation.2.16 S rRNA sequencing showed that Bacteroidetes and Firmicutes were the first two dominant phyla and Bacteroides was the most dominant genus of 14-day-old suckling piglets.The relative abundance of Fusobacteria and Saccharibacteria in SF piglets increased compared with those in CON piglets.At the genus level,Bacteroides,Lactobacillus,and Roseburia were enriched in SF piglets;on the contrary,the genus Bilophila was reduced compare with those in CON piglets(P < 0.05).The PCoA based on weighted-unifrac distance revealed that the gut microbiota showed obvious segregation in CON and SF suckling piglets.The results showed that dietary treatment during pregnancy significantly changed the composition and structure of gut microbiota in suckling piglets.3.The levels of fecal and plasma acetate,butyrate,and total SCFAs in SF suckling piglets were higher when compared with those in CON piglets.Moreover,the plasma levels of zonulin,endotoxin,and diamine oxidase and the fecal levels of lipocalin-2 were decreased but plasma IL-10 and transforming growth factor-?(TGF-?)were increased in SF piglets when compared with those in CON piglets(P < 0.05).In addition,the levels of fecal ?-defensin-2(P < 0.05)increased in SF piglets.The genus Lactobacillus was positively correlated with ADG(P < 0.05)but negatively correlated with diarrhea rate(P < 0.05).The Bacteroides was positively correlated with plasma IL-10(P < 0.05).Additionally,the genus Bilophila was positively correlated with fecal lipocalin-2(P < 0.05).These results suggested that the improvement of intestinal barrier and growth rate of piglets by dietary fiber during pregnancy may be related to the regulation of gut microbiota composition and metabolism in piglets.In summary,the main conclusions of this study are as follows:(1)The breeding sow undergoes metabolic syndrome during perinatal period.Besides,increased gut permeability and plasma endotoxin levels caused by negative microbial changes and decreased butyrate production would possibly be the potential mechanisms under which sow's metabolic disorders were exacerbated during perinatal period.Moreover,obesity in late pregnancy aggravated the metabolic disorder of sows during perinatal period,reduced the number of live piglets and litter weight of piglets,and affected the intestinal health of piglets.(2)Dietary SF during pregnancy effectively ameliorates perinatal metabolic syndrome in sows.The potential mechanism is that SF in pregnancy diet prevents pregnancy-induced the decrease of butyrate-producing bacteria and butyrate production,thereby reducing intestinal permeability and plasma endotoxin concentrations in sows during perinatal period.(3)Dietary SF during pregnancy changed the source of gut microbiota of newborn piglets-the composition of sow fecal and milk microbiota,improved the colonization of gut microbiota in newborn piglet,thereby improving growth performance of suckling piglets. |
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