Effects Of Daily-phase Feeding Program On The Changes Of Digestive Enzymme Activity And Gut Microbes In Growing-finishing Pigs

The nutritional requirements of pigs continuously changes with growth.By increasing the feeding phase,the animal performance and economic benefits of growing-finishing pigs can be improved,and the excretion of nitrogen and phosphorus can be effectively reduced.In recent years,studies has payed much attention to the gut microbes which can participate in various physiological activities such as regulating nutrient metabolism and immunity of the host,affecting animal growth and health.It has not been reported whether the daily-phase feeding of growing-finishing pigs will affect the host gut microbes and nutrient metabolism.Therefore,the purpose of this experiment is to investigate the effects of daily-phase feeding on performance,nutrient utilization,and gut microbes of growing-finishing pigs.A total of 240 healthy piglets of 80-day-old(about 34 kg)with the same genetic background were randomly divided into two groups with eight replicates in each group and fifteen piglets in each replicate,and the experiment trial lasted for 100 days.Five-phase feeding(FPF)and daily-phase feeding(DPF)were used.At the end of the trial,one pig was randomly selected from each replicate for slaughter.The test results are as follows:1)The DPF group can significantly reduce the feed conversion rate,the crude protein intake per unit weight and the feed cost per unit weight gain of that in the FPF group(P<0.05);there was no significant difference in the starting body weight,the final body weight,the average daily feed intake and the average daily gain between the DPF group and the FPF group(P>0.05).2)The serum concentration of total protein in the DPF group was significantly lower than that in the FPF group(P<0.05);the concentration of alkaline phosphatase in serum of the DPF group was significantly higher than that in the FPF group(P<0.05);there was no significant difference in the concentration of urea nitrogen,glucose,albumin,alanine aminotransferase and aspartate aminotransferase between the DPF group and the FPF group(P>0.05).3)The duodenal alkaline phosphatase and Na~+-K~+ATPase activities in the DPF group were significantly higher than that in the FPF group(P<0.05);the jejunal alkaline phosphatase activities in the DPF group were significantly higher than that in the FPF group(P<0.05).There was no significant difference in jejunal Na~+-K~+ATPase activity between the two groups(P>0.05).4)The villi height in duodenum and jejunum of the DPF group was significantly higher than that in the FPF group(P<0.05),and the ratio of villi height/crypt depth was significantly lower than that in the FPF group(P<0.05).The duodenal crypt depth of the DPF group was significantly lower than that in the FPF group(P<0.05),and there was no significant difference in jejunum crypt depth between the two groups(P>0.05).5)Compared with the FPF group,the DPF group can significantly increased the m RNA expression of alanine-serine-cysteine transporter 2(ASCT2)in duodenal,cationic amino acid transporter 1(CAT1)in jejunum and glucose transporter type 2(GLUT2)in ileum(P<0.05);there was no significant difference in the m RNA expressions of sodium-dependent glucose transporter 1(SGLT1)and peptide transporters 1(PEPT1)in small intestine between the two groups(P>0.05).6)The results of 16Sr DNA sequencing showed that there was no significant difference in the alpha diversity of gut microbes between the two groups(P>0.05).At the level of phylum,it is mainly composed of Bacteroides,Pachyphyta,Borrelia,Proteus,but there is no significant difference in their relative abundance.At the genus level,the relative abundance of Oscillospira,Ruminococcu in the DPF group was significantly higher than in the FPF group,the relative abundance of RFN20 in the DPF group was significantly lower than in the FPF group.At the species level,the relative abundance of Ruminococcus gnavus,Streptococcus equi in the DPF group was significantly lower than in the FPF group,the relative abundance of Clostridium methylpentosum in the DPF group was significantly higher than in the FPF group.7)A total of 4331 metabolites were identified in the plasma metabolome,and 342differential metabolites were screened.Compared with the FPF group,248metabolites were significantly up-regulated and 94 metabolites were significantly down-regulated in the DPF group.The metabolic pathway enrichment analysis of differential metabolites based on the KEGG database found that the metabolic pathways that were significantly enriched were lipid metabolism,amino acid metabolism and vitamin metabolism.According to the above results,it can be known that daily-phase feeding can significantly reduce the feed conversion ratio of growing-finishing pigs and save feed costs.Daily-phase feeding can change the structure of the gut microbes,improve intestinal morphology,promote nutrient transport and absorption,and regulate the metabolism of amino acids,lipids and vitamins.Daily feeding can reduce the abundance of harmful bacteria such as Ruminococcus gnavus and Streptococcus equi.The plasma lipid metabolism and amino acid metabolism related products are significantly increased,thereby promoting intestinal health and improving production performance.