Effects Of Early Milk Replacer Supplementary On Bacterial Community And Metabolites In Hindgut Of Pre-and Post-weaning Piglets

The sow milk is not adequate for all newborn piglets due to the increasing number of piglets in the rapid development of modern pig industry.The early milk replacer supplementary during the lactation period can reduce diarrhea frequency of weaning piglets by exercising the intestinal function and improving the adaptability of dietary.What is the mechanism that milk replacer can decrease the diarrhea rate of weaning piglets?At present,people are mainly focused on the digestion function and absorption function of small intestine,limited information related to the effects of gut microbiota on the diarrhea rate of weaning piglets are reported.The gut microbiota is essential to maintain the intestine and host health.The gut microbiota not only constitutes the host microenvironment,but also participates in energy metabolism,immune regulation and signal transmission.To deeply understand the changes and effects of gut microbiota due to milk replacer supplementary,we measured the bacterial composition and metabolites in cecum and colon of pre-and post-weaning piglets to explore the relationship between diarrhea and gut microbiota.This paper is divided into three parts.1.Effects of early supplementary feeding milk replacer on the growth performance and diarrhea frequency of pre-and post-weaning pigletsThis paper reports the investigation of the effects of early supplementary feeding milk replacer on the growth performance and diarrhea frequency of pre-and post-weaning piglets.In this study,10 litter of Duroc x Landrace x Yorks newborn piglets were randomly divided into two groups of five litters(the control group and the treatment group).The piglets in the control group were reared by the sow,while the piglets in the treatment group were supplemented with a milk replacer along with suckling from the 4th to 28th day of age.All piglets were weaned on the 28th day,then switched to the same diet and stayed on the diet for 7 days.On the 28th and 35th day,the samples of piglets were collected for analysis.Compared with the piglets in the control group,the post-weaning piglets in the treatment group had a lower diarrhea frequency(P = 0.08).There were no statistical difference on the immune organ weight,the concentrations of immunoglobulin in serum,the mucosal morphology in colon and cecum of piglets on the 28th and 35th day(P>0.05).In addition,the milk replacer supplementary increased the colonic mucosa thickness of piglets in the treatment group on the 28th day(P<0.05),and decreased the concentration of sIgA in colonic mucosa on the 35th day(P<0.05).The results suggest that early milk replacer supplementary didn't affect the growth performance,the systemic immunity and the development of the large intestine of the piglets before and after weaning,but could reduce the diarrhea frequency after weaning.2.Effects of early supplementary feeding milk replacer on cecal bacterial community and metabolites of pre-and post-weaning pigletsThis paper reports the investigation of the effects of early supplementary feeding milk replacer on cecal bacterial community and metabolites of pre-and post-weaning piglets.The experiment design was same as that of chapter 1.Results showed no statistical difference on the pH value and the concentrations of ammonia nitrogen and lactic acid in the colonic digesta of piglets in the two groups on the 28th and 35th day(P>0.05).The milk replacer supplementary increased the concentrations of propionate and total SCFAs in the treatment group on the 35th day(P<0.05).DGGE analysis showed that bacterial diversity in the treatment group was similar as that in the control group on the 28th day and 35th day(P>0.05).RT-PCR analysis showed that early milk-replacer supplementary decreased the quantity of Escherichia coli in cecal digesta on the 28th day(P<0.05),but didn't change quantity of the total bacteria,Firmicutes,Lactobacillus,Clostridium ? and Clostridium XIVa on the 28th and 35th day(P>0.05).The results suggest that the early milk replacer supplementary didn't affect the bacterial diversity and the quantity of dominant bacteria in cecum,but could decrease weaning diarrhea rate of piglets by reducing the quantity of Escherichia coli before weaning and increasing the concentrations of propionate and total SCFAs after weaning.3.Effects of early supplementary feeding milk replacer on colonic bacterial community and metabolites of pre-and post-weaning pigletsThis paper reports the investigation of the effects of early supplementary feeding milk replacer on colonic bacterial community and metabolites of pre-and post-weaning piglets.The experiment design was same as that of chapter 1.Results showed that the concentrations of acetate,propionate,butyrate,valerate and branch chain fatty acids(BCFAs)in the colonic digesta increased with the milk replacer supplementary in the treatment group on the 28th day(P<0.05).Pyrosequencing showed that the milk replacer supplementary didn't change the preponderant bacterial abundance in the phylum,family and genus levels(P>0.05),but increased the abundance of Paraprevotella(P = 0.05),Rumminococcus(P = 0.06),Clostridium XIVa(P-0.05),Succiniclasticum(P = 0.05),Clostridium IV(P = 0.06),Faecalibacterium prausnitzii(P = 0.10)and Ruminococcus bromii(P = 0.09),decreased the abundance of Lactobacillus,Clostridium XI,Blautia,Clostridium sensu stricto(P<0.05),Escherichia(P = 0.08)and Escherichia coli(P = 0.08)on the 28th day.In addition,the milk replacer supplementary decreased the expression level of interleukin-6(IL-6)(P<0.05),interferon-y(IFN-y)(P = 0.09)and tumor necrosis factor-a(TNF-a)(P = 0.08),but increased the expression level of toll like receptor 4(TLR4)(P<0.05)in the colonic mucosa on the 28th day.The concentrations of acetate(P<0.05)and total short chain fatty acids(SCFAs)(P = 0.05)increased in the treatment group compared with the control group on the 35th day.The milk replacer didn't change the colonic bacterial diversity in the treatment group on the 35th day(P>0.05).Real-time PCR showed that the quantity of Escherichiacoli(P=0.05),Lactobaclluswand Clstridium XlVa(P<0.05)decreased in the treatment group compared with the control group on the 35th day.In addition,the milk replacer supplementary increased the expression level of interleukin-6(IL-10)(P<0.05)and transforming growth factor-P(TGF-p)(P = 0.12)in the colonic mucosa of piglets in the treatment group otn the 35th day.The results suggest that early milk replacer supplementary didn't affect the bacterial diversity and structure in the colonic digesta,but can reduce the weaning diarrhea rate by adjusting the colonic bacterial composition,bacterial metabolites and the gene transcription related to the colonic function before and after weaning.