| Early weaning is an important part of pig production.During the weaning process,due to the conversion of the diet from breast milk to pellet feed which is rich in cereal raw materials,coupled with changes in the external environment,the gut microbiota established by using breast milk as a substrate occurs.Drastic changes cause the intestinal flora of piglets to be disordered,destroying the intestinal microbial barrier,increasing the risk of colonization of pathogenic bacteria,causing diarrhea in piglets and seriously affecting the growth performance of piglets.Synbiotics are a combination of probiotics and prebiotics that work together to produce beneficial effects.Studies have shown that synbiotics have functions such as improving piglet growth performance,promoting intestinal development,and regulating gut microbiota,but the specific mechanism is still unclear.Lactobacillus and Clostridium butyricum are widely reported which have beneficial effects.Inulin and fructooligosaccharides are prebiotics.In this paper,we studied the regulation of the combination of the above two probiotics and probiotics on the intestinal flora and metabolism of weaned piglets,and explored its mechanism of relieving weaning stress and improving growth performance.At the same time,determine the best use time period,and provide the basis for the application of the synbiotics in pig production.This study is divided into the following three parts:1 Screening of the best compatibility of the synbiotics and its effect on growth performance of nursery pigsThe aim of this trial was to combine two probiotics and two prebiotics to screen for optimal compatibility and to assess the probiotic effects of synbiotics on the growth performance of nursery pigs.The experiment selected 1200 healthy weaned piglets of similar body condition(6.35 ± 0.20 kg)and weaned at 21 days of age,using completely randomized block design,and divided into nine experimental groups according to the orthogonal test design of 4 factors and 3 levels.At the same time,a control group was set up,with three replicates in each group and 40 piglets per replicate.Each of the experimental groups fed a synbiotic composed of Lactobacillus sporogenes,Clostridium butyricum,inulin and fructooligosaccharides by drinking water.The dose levels of each component of each group of fed synbiotics correspond to the dose levels of the components in the orthogonal table.The test period was 49 days,fed daily at 21-42 days of age,and fed each other day at 42-70 days of age,with a doubled dose.The control group received normal drinking water.The results show that the optimal combination of levels is selected by orthogonal test,corresponding to the seventh combination in orthogonal tables.Compared with the control group,synbiotics significantly increased the average daily feed intake and average daily gain of 21-42 days old(P<0.05);significantly reduced the diarrhea rate of nursery pigs(P<0.05);significantly increased the average daily gain of 42-70 day old nursery pigs(P<0.05),and had no significant effect on average daily feed intake,feed-to-weight ratio and diarrhea rate(P>0.05).In summary,the results show that the best compatibility of a synbiotic can significantly improve the growth performance of nursery pigs,and has a certain probiotic effect.2 Effects of synbiotics on the microbial community and concentrations of short chain fatty acids in feces of nursery pigsThis experiment aims to analyze the effect of synbiotics on the gut microbiota of nursery pigs by analyzing the structure of fecal microbiota in 21-70 days old pigs.The changes in the concentration of lactic acid and short-chain fatty acids in the feces were analyzed to synthesize the beneficial effects of synbiotics.On the basis of the first chapter experiment,the stool samples of the seventh group and the control group at 21,28,42 and 70 days old were collected.The structure of fecal microbiota was analyzed by Hiseq sequencing,and the short-chain fatty acid content of feces was determined by gas chromatography.High-throughput sequencing of 16S rRNA showed that the synbiotics had no significant effect on the diversity and abundance of fecal microbiota(P>0.05),but significantly increased the relative abundance of Lactobacillus in the feces of 28-day-old piglets and the relative abundance of Prevolla in the feces of the 42-day-old piglets.After treatment with synbiotics,the pH of the 28-days-old,42-days-old nursery pig feces was significantly reduced in the treatment group(P<0.05).The use of synbiotics significantly increased the concentration of lactic acid in the fecal pigs of the 28-days-old pigs in the treatment group.It can be seen that the use of synbiotics can significantly increase the total short chain fatty acids and butyric acid concentrations in pig feces during the nursery period(P<0.05);significantly increase the acetic acid concentrations in the feces of 28 and 42-days-old pigs(P<0.05);There was no significant effect of propionic acid concentrations in feces(P>0.05).Correlation analysis showed that the content of acetic acid and butyric acid in feces was significantly negatively correlated with the rate of diarrhea in nursery pigs,and was significantly positively correlated with average daily gain and average feed intake.In summary,supplementation of synbiotics changed the structure and metabolism of intestinal flora of weaned piglets and improved their growth performance.3 Evaluation of long-term beneficial effects of synbioticsThis chapter aimed to determine the changes in the structure of pig intestinal flora by high-throughput sequencing by measuring the slaughter performance and meat quality of the pigs.Assess whether there was a certain long-term effect of using the synbiotics during the nursery period.The results showed that there was no significant effect on the slaughter performance and meat quality of pigs after the use of synbiotics in the nursery period(P>0.05).For the bacterial alpha diversity of each intestinal segment,the main indicators were Chao1 index,OTU numbers,Shannon index,Simpson index.There was no significant effect on these index(P>0.05).In the ileum,compared with the control group,the relative abundance of Firmicutes treated with the synbiotics during the nursery period increased(P=0.09),and the relative abundance of Bacteroides in the treatment group decreased(P=0.08).At the genus level,the relative abundance of Actinobacillus in the ileal after treatment with synbiotics was significantly lower(P<0.05).Unclassified Clostridiaceae has an upward trend(P=0.07).In the colon,the early synbiotics treatment increased the relative abundance of Lactobacillus in the colonic contents(P=0.07).In summary,synbiotics can improve the growth performance of nursery pigs,increase their average daily gain,and reduce the diarrhea rate of weaned piglets.Feeding synbiotics changed the microbiota of feces and produced a variety of bacterial metabolites to improve the growth perfermance of the nursery pigs.Feeding synbiotics during the nursery period can partly adjusting gut microbiota,slaughter performance and meat quality. |
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