| China is the largest country for pork consumption in the world.Pork and its processed products play an irreplaceable role in the diet structure of Chinese consumers due to their unique quality and nutritional value.With the rapid development of the Chinese economy,the improvement of living standards for urban and rural residents,and the continuous expansion of consumer groups,the demand for meat products is gradually increasing.Therefore,reducing production costs,improving the slaughter rate of fattening pigs,and ensuring the health status of pigs are crucial for enhancing the economic benefits of the pig industry.Trillions of microbiota inhabit the gut of animals,including humans.The gut microbiota plays a crucial role in the host’s life activities and immune regulation.In addition,the gut microbiota can produce a variety of small-molecule metabolites,including short-chain fatty acids(SCFAs),secondary bile acids,and indole derivatives,through the fermentation of dietary nutrients.These metabolites further participate in regulating host behavior and maintaining internal environmental homeostasis.In clinical practice,microbiota and their metabolites have been applied to the study of numerous human diseases,including obesity,inflammatory bowel disease,cardiovascular disease,neurodegenerative diseases,and cancer.This suggests that regulating the growth performance of pigs through gut microbiota is particularly important for ensuring the steady development of the pig farming industry.This study focuses on commercial Duroc pigs in good health that have not received antibiotic treatment to explore the effects of gut microbiota on the growth traits(residual feed intake,daily feed intake,daily weight gain)of experimental pigs and their potential mechanisms of action.We utilized both 16 S r RNA gene V3-V4 hypervariable region sequencing and shotgun metagenomic sequencing to investigate the gut microbial composition associated with specific phenotypes.And we used fecal SCFAs and serum metabolomics data to analyze the potential mechanism of the gut microbiota on host phenotype by using the two-part model,co-abundance groups(CAGs),spearman correlation analysis,and other diversified analysis methods.This study is divided into two parts.The main contents are as follows:1.Fecal and serum samples were collected at 140 days from 208 Duroc pigs in good health.We first performed 16 S r RNA gene and metagenomic sequencing analysis to investigate the relationship between the gut microbiome and porcine residual feed intake(RFI).16 S r RNA gene sequencing analysis detected 21 OTUs showing the tendency to correlation with the RFI(P < 0.01).Based on the Spar CC method,CAGs analysis was performed on OTUs after quality control,and eight CAGs were obtained.Among them,CAG1,which was composed of 112 OTUs and with Ruminococcaceae as the core bacteria,was significantly negatively correlated with the phenotypic value RFI(P < 0.05).Metagenomic sequencing further identified that the members of Clostridiales,e.g.,Ruminococcus flavefaoiens,Lachnospiraceae bacterium 28-4,and Lachnospiraceae phytofermentans,were enriched in pigs with low RFI(high-FE),while 11 bacterial species including 5 Prevotella spp.,especially,the Prevotella copri,had higher abundance in pigs with high RFI.Functional capacity differential analysis of gut microbiota in pigs with high and low RFI suggested that the gut microbiome of low RFI pigs had a high abundance of the pathways related to amino acid metabolism and biosynthesis,but a low abundance of the pathways associated with monosaccharide metabolism and lipopolysaccharide biosynthesis.Serum metabolome and fecal shortchain fatty acids were determined by UPLC-QTOF/MS and gas chromatography,respectively.Propionic acid in feces and the serum metabolites related to amino acid metabolism were negatively correlated with the RFI.2.In this experiment,the growth traits of 205 Duroc pigs in good health aged 90-170 days were recorded,and serum and fecal samples were collected at 140 days for the analysis of serum metabolites and gut microbiota.Subsequently,a variety of biostatistical methods were used to screen the microbiota markers that affect the daily weight gain and feeding behavior of pigs.The CCA analysis results indicate that the environment(measurement station),genetics(sex,kinship),and experimental processing(experimental batch)all have an impact on gut microbiota.The results of enterotype analysis revealed that the ADG and ADFI of enterotype 1,dominated by Oscillospira,were significantly lower than those of enterotype 2,dominated by Prevotella.A total of 4 CAGs were obtained by analyzing OTUs after quality control using the CAGs method.Among them,CAG4,composed of 125 OTUs and with Clostridia as the core bacterium,showed a significant negative correlation with phenotypic values of ADG and ADFI(P < 0.05).A significant negative correlation between Faecalibacterium prausnitzii and phenotypes(ADG and ADFI)was identified in both 16 S r RNA sequencing and metagenomic sequencing analysis(P < 0.05).The OTUs obtained from 16 S r RNA sequencing were analyzed using weighted correlation network analysis(WGCNA),and the results showed that Module3(ME3)and Module4(ME4)were significantly negatively and positively correlated with phenotypes(ADFI and ADG),respectively(P < 0.05).It is worth mentioning that ME4-related metabolites are significantly enriched in valine,leucine and isoleucine biosynthesis and valine,leucine and isoleucine degradation pathways,which are similar to the results of metagenomic differential analysis.In addition,isovaleric acid in fecal SCFAs was significantly negatively correlated with ADG(P < 0.05)and propionic acid was negatively correlated with ADFI(P < 0.05).The results of this study can provide a reference for the biomarkers of pig feeding behavior and daily weight gain to screen potential gut microbiota and metabolites.The research results of this paper preliminarily explored the correlation between gut microbiota and pig growth performance,and identified the categories of gut microbiota related to feed efficiency,daily weight gain,and feeding behavior.Microbial-derived metabolites,such as SCFAs,amino acids,and their derivatives,have important regulatory functions for host metabolic health and energy homeostasis.Combined with fecal SCFAs and serum metabolomics data,we have revealed the potential correlation between gut microbiota and metabolites.Furthermore,we have proposed a possible mechanism through which gut microbiota regulates pig growth performance.Our research may provide potential biomarkers of gut microbiota that can be utilized to improve feed efficiency in the pig industry.In particular,pigs are an ideal animal model,the results of this study also have significant implications for seeking strategies to regulate human body weight and appetite. |
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