| The increasingly prominent issues in China include the scarcity of feed protein resources and the growing nitrogen emissions.However,the reduction in dietary protein levels limited the rate of amino acid metabolism and decreased growth performance of pigs.To explore the amino acid metabolism pattern of growingfinishing pigs was the foundation for improving nitrogen nutrient utilization efficiency.Simultaneously,reducing the oxidation metabolism of amino acids as energy and urea production served as an important strategy for reducing nitrogen emissions.Therefore,the aim of the study was to investigate the metabolism rules of amino acid in the intestinal and the liver of growing-finishing pigs at the age of d 90,d 120,d 150,d 180 and d 210,and perform correlation analysis of amino acid metabolites,biochemical indicators and intestinal flora.A total of 50 boars(Duroc × Landrace × Large White)(36.48 ± 0.72 kg)at the d90 were used for the trial.The trials started at d 90 and ended at d 210.The trial was divided into 2 stages,D 90-120 and D 120-210.8 pigs were randomly selected at the age of d 90(D 90),d 120(D 120),d 150(D 150),d 180(D 180)and d 210(D 210)for the purpose of fasting weighing,followed by slaughter,liver,kidney and spleen was weighed,and samples of the liver tissues,the jejunal mucosa and the colonic digesta were collected.Amino acid metabolizing enzymes: Analysis of the activities of metabolic enzymes associated with the ornithine cycle in the intestine and liver of growingfinishing pigs.The results showed that: Compared with the D 180,the carbamoylphosphate synthase-I and Ornithine carbamoyl transferase activities of the liver of pigs were significantly decreased in the D 210(P < 0.05);The glutamate dehydrogenase activity of the liver was significantly higher in pigs at the D 120,D 180 and D 210 than that in the D 90(P < 0.05).Compared with the D 90,the glutamine synthetase activity of the jejunal mucosa of the liver was significantly decreased in the D 150(P < 0.05);The glutamate dehydrogenase and the alanine aminotransferase activities in the jejunal mucosa of growing-finishing pigs in the D 210 were higher than those of the pigs in the D 90 and D 150(P<0.05).Amino acid metabolites and regulatory pathways: Analysis of intestinal amino acid transporters,hepatic amino metabolites and intestinal and hepatic m TORC1 signaling pathways in growing-finishing pigs.The results showed that:(1)Intestinal amino acid transporters.The m RNA expressions of ornithine transporter of the jejunum mucosa in the D 180 were higher than those of the pigs at the age of D 150 and D 210(P < 0.05);Compared with the D 90,the pigs at the age of D 120 and D 180 showed significantly upregulated m RNA expressions of taste 1 receptor type member 3in the jejunal mucosa of pigs(P < 0.05).(2)Hepatic amino acid metabolites.A total of thirty-one hepatic differential metabolites were detected,which mainly affect tryptophan and glutamate metabolism.The content of kynurenine of the liver was higher at the age of D 150,D 180,and D 210 than the D 90(P < 0.05),with no significant difference at the age of D 120,D 150,D 180 and D 210(P > 0.05).(3)m TORC1 signaling pathway.Compared with D 150,the liver m TOR phosphorylation levels at the age of D 180 and D 210 had a tendency to decrease(P = 0.057).Gut microbiota and analysis of metabolic and microbial correlations: Analysis of intestinal microbiota and Spearman correlation in growing-finishing pigs.The results showed that(1)Colonic microorganisms.The relative abundances of Actinobacteriota and Spirochaetota were increased at the age of D 210(P < 0.05),and the relative abundances of Ruminococcus at the age of D 150,D 180 and D 210 were higher than those at the age of D 90(P < 0.05);The relative abundances of Lactobacillus at the age of D 180 and D 210 were significantly lower than those of the D 120(P < 0.05).(2)Spearman correlation analysis.The content of 5-hydroxytryptamine in the liver of pigs was negatively correlated with Lactobacillus(|r| = 0.42,P < 0.05);The content of hepatic kynurenine was positively correlated with Treponema(r = 0.44,P < 0.05),Spirochaetota(r = 0.43,P<0.05),Oscillospira(r = 0.56,P < 0.05)and Terrisporobacter(r = 0.73,P<0.05);The aspartate aminotransferase activity of the liver was positively related to the content of kynurenine(r = 0.40,P < 0.05);The content of hepatic urea nitrogen was positively correlated with γ-aminobutyric acid(r =0.48,P < 0.05)and N’-formyl kynurenine(r = 0.42,P < 0.05).Collectively,hepatic ornithine cycle-related metabolic enzyme activities were decreased in growing-finishing pigs at D 210 compared to D 180.Compared with the D 90,intestinal glutamine cycle-related metabolic enzyme activities were enhanced in growing-finishing pigs at D 120,D 180 and D 210;The abundance of intestinal anaerobic bacteria in pigs increased significantly at D 150、D 180 and D 210,while the composition and structure of intestinal flora in growing-finishing pigs tended to be similar at the D 180 and D 210.The variation in hepatic amino acid metabolism in pigs of different ages was mainly enriched to tryptophan and glutamate metabolism.Intestinal amino acid transporter and amino acid receptor m RNA levels did not change with the age of growing fattening pigs.Different aging has an effect on the level of hepatic m TOR phosphorylation in growing-finishing pigs. |
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