Effects Of Dietary Iron Concentration On Growth Performance And Hindgut Microbiota Compositon And Metabolites Of Growing-finishing Pigs

Iron is an important trace element for animal to promote growth and regulate gut microbiota,and imbalance of dietary iron supply would lead to host iron homeostasis disorder which could affect microbiota composition and diversity.1200 pigs(Yorkshire× Landrace × Duroc)with an initial body weight of about 27 kg were selected for this experiment,half of which were male and others were female.All the pigs were randomly divided into five group,and Fe SO4 was added to basal diet on a different concentration(0,150,300,450 or 600mg/kg).There were 8 replicates per group and 30 pigs per replicate,and this experiment was lasted for 4 months.This study investigated the effect of feeding growing-finishing pigs with different concentration of dietary Fe SO4 on their growth performance,serum biochemistry and body iron status.Besides,we also analyzed the effect on gut microbiota and metabolites based on 16 S r RNA sequence and metabolome analysis.The main results are as follows:1.Effect of dietary iron concentration on growth performance,serum biochemistry and iron Status of growing finishing pigs.As the dietary iron concentration increased,average daily feed intake(linear,P =0.02),average daily body weight gain(linear,P = 0.02)and body weight(linear,P =0.02)in growing stage(61-110 kg)was increased linearly.Besides,the concentrations of serum cholesterol(CHOL)and serum low-density lipoprotein(LDL)showed a quadratic curve,increasing first followed a decreasing(quadratic,P < 0.05).Compared to control group,serum unsaturated iron binding force(UIBCI)decreased significantly after iron supplementation,and serum iron(SI)concentration increased linearly(linear,P < 0.05),the contents of iron in spleen,liver and intestinal tract were linearly increased with the increase of dietary iron concentration(linear,P < 0.05).2.Effects of dietary iron concentration on the structure of colonic microbiota in growing finishing pigs.Colon contents of growing-finishing pigs fed diets with different iron concentrations for 4 months were collected for 16 S r RNA sequencing.Our results showed that the dominant phylum in the colon were Firmicutes and Bacteroidetes,and the dominant family were Muribaculaceae and Ruminococcace,while the dominant genus in colon were Lactobacillus and Uncultured＿bacterium＿f＿muribaculaceae.There was no significant difference in intestinal microbiota at the taxonomic level of phylum,family and genus with different iron concentration diets.3.Effects of dietary iron concentration on the structure of colonic microbiota in growing finishing pigs.Rectal contents of growing-finishing pigs fed diets with different iron concentrations for 4 months were collected for 16 S r RNA sequencing.Our results showed that the dominant phylum in the rectal were Firmicutes and Bacteroidetes.At phylum level,the relative abundance of Bacteroidetes and Proteobacteria varied significantly.Compared to 0mg/kg group and150mg/kg group,the relative abundance of Proteobacteria was markedly increased in 450mg/kg group and 600mg/kg group.Compared to 0mg/kg group,the relative abundance of Bacteroidetes was decreased in600mg/kg group(P < 0.05).The dominant family in the rectal were Muribaculaceae and Ruminococcacea.Compared to 0mg/kg group,the relative abundance of Clostridiaceae was increased(P < 0.05)and the relative abundance of Muribaculaceae was decreased(P < 0.05).The dominant genus in the rectal were uncultured＿bacterium＿f＿Muribaculaceae and Streptococcus.The relative abundance of Streptococcus decreased firstly and then increased with dietary iron concentration increasing(P < 0.05).Compared to 0mg/kg,the relative abundance of uncultured＿bacterium＿f＿Muribaculaceae was decreased(P < 0.05).4.Effect of 0mg/kg group and 600mg/kg group on the metabolites of rectum contents of growing finishing pigs.Rectal contents of growing-finishing pigs fed diets with different iron concentrations for 4 months were collected for metabolome analysis.Compared to 300mg/kg group,0mg/kg group was more enriched in amino acid metabolism pathway and short-chain fatty acid metabolism pathway,including phenylalanine metabolic pathways,aminoyl biosynthesis pathways,and butyric acid metabolic pathways.Besides,the metabolites increased in 0mg/kg group included butyric acid,phenylalanine,tyramine,etc.Compared to 300mg/kg group,more differential metabolites in 600mg/kg group were enriched in the phenylalamine metabolism pathway.The metabolites increased in600mg/kg group included phenylacetic acid,phenylpyruvate,etc.In conclusion,the growth performance of finishing pig was improved with the increase of dietary iron supplementation,but the microbiota of colonic microbiota in growing and finishing pigs were relatively stable.While rectal microbiota significantly changed,iron deposition in organ was correlated with the change of rectum microbiota.Based on rectal metabolome analysis,0mg/kg group and 600mg/kg group markedly changed intestinal microbial metabolites and metabolic pathways,compared to 300mg/kg group.Besides,the beneficial metabolites of microbiota in the low iron group(0mg/kg)were higher,while the harmful metabolites in the high iron group(600mg/kg)were higher.