| Pork is the main type of meat consumped by people in China,so pig production is a vital industry of China's agriculture.Gut microbiota plays important roles in influencing economically important traits,such as feed efficiency and fat deposition.Recent studies have shown that the interaction between sex hormones and gut microbiota can cause many hormone-related diseases,such as polycystic ovary syndrome.Puberty is a very important reproductive trait in gilts.The failure of puberty onset is mainly caused by the disorder of steroid hormone secretion.However,it is not clear whether the gut microbiota is related to puberty by regulating the sex hormones.In addition,vaccines play a significant role in disease prevention and control in pig farms.It has been found that inter-individual variation in antibody responses to vaccines reslut in inconsistent immune protection in the herd,and thereby bring risks in preventing and controlling disease on farm.In recent years,the studies on human influenza vaccines have found that gut microbiota is one of the important reasons for different levels of vaccine-specific antibodies among individuals.However,whether gut microbiota affects the different levels in vaccine-specific antibodies between pigs remains unknown.Therefore,in this study,we investigated the effects of gut microbiota on sow puberty and vaccine-specific antibody levels.We first explored the possible relationship between the failure of observe oestrus and the composition of gut microbiota in gilts.We also evaluated the changes of the gut microbiota along with the stages of a heat cycle and identified the gut bacterial taxa related to failure to observe oestrus in gilts.And then analyzed the association between gut microbiota and the variations of antibodies induced by vaccines in pigs,and identified the bacterial taxa that may be involved in the production or maintenance of vaccine-specific antibodies.We calculated the contribution of gut bacteria to the variation of vaccine-specific antibody levels.The details of results are described in the following:We first compared the gut microbial composition between 73 gilts failure to enter oestrus at age of 9.5 months and 90 full-sib or half-sib counterparts showing normal heat cycle.The results of 16 S rRNA sequencing suggested that Prevotella,Treponema,Faecalibacterium,Oribacterium,Succinivibrio and Anaerovibrio and were enriched in the gilt showing normal oestrus,while Ruminococcaceae,Lachnospiraceae,Ruminococcus,Coprococcus,and Oscillospira had higher abundances in the gut of gilt failing to enter oestrus,indicating that these bacterial taxa have an important effect on puberty of gilts.Predicted functional capacity analysis suggested that gut microbiota should be related to oestrus through retinol metabolism.We explored the shifts of the gut microbiota along with four stages throughout a heat cycle in 22 gilts.The co-occurrence network analysis of gut microbiota showed that a module containing Sphaerochaeta and Treponema was found since gilts entered the heat cycle.In the second study of this thesis,feces and blood samples were collected from 198 gilts.Microbial DNA from feces were extracted,and V3-V4 hypervariable region of 16 S rRNA gene was sequenced.Antibody levels of classical swine fever,and swine reproductive and respiratory syndrome were determined in blood of all 198 gilts.Antibody levels of swine pseudorabies,swine japanese encephalitis and swine parvovirus were also determined in 49 gilts out of 198 gilts.The two-part models were employed to identify the bacterial taxa significantly associated with the vaccine-specific antibody levels.The results implied that the vaccine-induced antibody levels varied among pigs.Ruminococcaceae,Lachnospiraceae,Oscillosporia,and Prevotella are associated with vaccine-specific antibody levels of four or five kinds of vaccines.The results showed that the gut microbiome could account for 1.11%-9.35% of the variation in the antibody response.In addiotion,we identified three CAGs showing significantly different abundance between positive and negative response gilts of classical swine fever.CAG11 dominated by Lactobacillus and CAG12 dominated by Prevotella showed higher abundance in positive response gilts,whereas CAG15 comprised of Coprococcus?catus,Butyricicoccus?pullicaecorum,unclassfied Ruminococcaceae and unclassfied Bacteroidales had higher abundance in negative response gilts.This study suggested that gut microbiota should play an important role in puberty in gilts.The bacteria associated with estrogen and the disorders of retinol metabolism in gut microbiome may be important biomarkers for the failure to observe oestrus.This improved our understanding of the mechanism of puberty in gilts,and provides a certain scientific basis for regulation of gilt puberty in gilts by administrating probiotics or prebiotics.In addition,we found that gut microbiota may affect the vaccine-specific antibody levels.This resluts provides a reference for the design of pig vaccines and the exploration of gut microbiota as an endogenous immune adjuvant. |
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