Vertical Transmission Of Sows' Microbiota Affects Microbial Colonization And Functional Development Of Intestine In Piglets

In this study,sow-piglet model was used to study the changes of intestinal microorganisms during maternal reproductive cycle and the colonization and development of intestinal microorganisms in offspring.In Exp.1,the shift of intestinal microbial structure and metabolites in sows during reproductive cycle were determined.Eight Landrace sows and nine Rongchang sows were selected to collect stool samples at different time points during pregnancy(35 days,70 days,106 days after mating),lactation(3 days,7 days,14 days,28 days after parturition),and non-pregnancy period(12 days after weaning).Using 16S rRNA gene sequencing technique,Coriobacteriaceae was found to gradually increase over gestational time irrespective of breed,which was further validated in an independent cohort of sows,indicating that Coriobacteriaceae is likely associated with the progression of pregnancy.Escherichia increased as well.Relative to empty and gestation,lactation was associated with an increase in SCFA producers and a concomitant augmentation in SCFA production in both breeds.A comparison between the two breeds revealed that Ruminococcaceae was more abundant in RS than LS,consistent with a strong ability of Rongchang pigs to digest highly fibrous feedstuffs.In Exp.2,the shift of nutritional components and microbial community in breast milk of sows during lactation were determined.The results showed that the concentrations of protein and dry matter decreased gradually(P<0.05),carbohydrate increased gradually,but the levels of fat and energy were relatively stable.In addition,the levels of IgG and IgA were the highest in colostrum,which largely depleted rapidly after birth and then gradually diminished by day 35.Lactococcus,Halomonas,Bacillus and Lactococcus were the dominant bacteria,and the abundance of Bacillus decreased gradually after birth and then stabilized gradually.Microbes from skin,vagina and environment of sows constituded three main sources of microorganisms in breast milk.In Exp.3,the colonization of mucosa-associated microbiota in jejunum,ileum,cecum and colon of neonatal piglets within 35 days after birth was studied.The results showed that the intestinal site was the main factor affecting the variation of mucosa-assocated microbiota,followed by the age.Breed showed no significant effect on the structure of intestinal mucosa-associated microbiota.Although they shared a similar composition at birth,the mucosal microbiome in the jejunum and ileum remained relatively stable,while those in the cecum and colon quickly epanded and diversified by day 35.Among microbial sources from mother(breast milk,vagina,feces,and areolar skin)and the birth environment(farrowing crate and incubator),the microbes from maternal breast milk and feces were primarily responsible for initial colonization of neonatal gut microbiota.The contribution of breast milk microorganisms to jejunum and ileum reached 80-90%and lasted until weaning.In contrast,although more than 90%of infant cecal and colonic microbiota was also originated from breast milk,but the contributions were gradually declined with age.On the other hand,the contribution of maternal fecal microbiota became progressively more prominent with age.Vaginal and environmental microorganisms contributed a small proportion to ileal,cecum and colonic mucosa-associated microbiota within a few days after birth,and then gradually decreased.In Exp.4,the relationship between intestinal barrier immune function and microbial colonization was explored.The results showed that intestinal site was the main factor affecting the expression of immune barrier function-related genes.The intestinal microbial colonization was significantly related to the expression of these genes,and showed a reverse spatial correlation pattern between the small intestine and large intestine,suggesting that the interaction between intestinal microbiota and host intestinal mucosal promoted the development and maturation of structure and function of the intestinal mucosa and antimicrobial peptides.More importantly,most of the microbes significantly related to expression of immune barrier functional-related genes can be found in the list of vertically transfered microbes,suggesting that maternal microbes may affect the development and maturation of the intestinal barrier immune system in offspring through vertically transferred microbes.In summary,maternal intestinal microbiota underwent phase-specific changes in composition and metabolites during the reproductive cycle,which might be involved in maternal metabolic changes and,together with breast milk microorganisms,constituted the main sources of intestinal mucosa-associated microbiota in the offspring.The interaction between mucosa-associated microbiota and intestinal mucosa promoted the co-development and maturation of the intestinal immune barrier funcrtion and intestinal microbiota.These intestinal mucosal microorganisms that significantly associated with the expression of immune barrier functional-related genes could be traced back to the mother through vertical transmission,which provides a theoretical basis for promoting metabolic health of mother during reproductive cycle and healthy development of offspring in earily life from the perspective of intestinal microbiota.