Effects Of Enzyme-added Expansion Of Corn On Starch Structure And Piglet Growth,intestinal Health And Glycolipid Metabolism

Due to the highly ordered crystal structure and high molecular weight,corn starch is difficult to digest and utilize by weaning piglets.Corn extrusion can destroy starch granule and crystal structure,and partially degrade the molecular structure through the action of high temperature,high pressure and shear force.However,due to the insufficient secretion of amylase by piglets during weaning,the improvement is limited.Therefore,improving the extrusion process method combined with enzymatic hydrolysis has the potential to further improve the digestibility of cornstarch.This paper intends to study the effects of extrusion temperature and enzyme-added expansion on the structure of corn starch and growth performance,intestinal health and glycolipid metabolism of weaning piglets,in order to establish the optimal process method of corn and improve the nutritional and feeding value of corn starch to piglets.This study consists of the following 4 parts:Exp.1 Effects of corn extrusion temperature on growth performance,intestinal health and glycolipid metabolism of weaning pigletsThe aim of this study was to investigate the effects of different extrusion temperatures on growth performance,intestinal health and glycolipid metabolism of weaning piglets,determining the appropriate extrusion temperature.Corn was either expanded(Expanded at 105℃ with an orifice diameter of 4 mm)or extruded(Extruded at 135℃ with an orifice diameter of 6 mm).108 thirty-d-old weaning piglets(Duroc× Landrace × Yorkshire)with initial body weight of 9.09 ± 0.14 kg were randomly assigned to 1 of 3 dietary treatments with 6 replicates per treatment and 6 pigs per replicate: 1)CON(control),2)EP(Expansion),and 3)ET(Extrusion).This study was conducted to investigate the effects of different extrusion temperatures on growth performance,intestinal health,and glycolipid metabolism of weaning piglets.Results showed as follows:(1)EP improved average daily gain(ADG)of weaning piglets(P < 0.05).(2)EP and ET significantly improved the jejunal activities of amylase,lipase,lactase,and sucrase as well as m RNA expressions of GLP-2,ZO-1,Occludin,Caludin-1,and Reg IIIγ genes,decreased serum DAO,D-lactate and LPS contents and increased serum CD4+/CD8+ T lymphocyte ratio(P < 0.05).(3)16S high-throughput sequencing analysis showed that ET significantly increased α-diversity(Shannon and Simpson index)increased significantly(P < 0.05),however,Lactobacillus abundance of which significantly decreased(P < 0.05).The analysis of KEGG pathway showed that the metabolic pathway with significant difference in EP was pentose phosphate metabolic pathway(P < 0.05),and which in ET was histidine metabolic pathway(P < 0.05).(4)EP and ET increased the activity of CPT-1 in the muscle of piglets,and the expressions of gluconeogenesis-related genes PCK1 and G6 PC in the liver and muscle(P < 0.05).EP increased the expression of CPT-1 in the liver and ET increased the expression of glycogen synthesis inhibitory gene GSK3β in muscle(P < 0.05);The results indicated that the low-temperature expansion of corn improved the growth performance of weaning piglets,which was related to the improvement of intestinal health and glycolipid metabolism.Exp.2 Effects of enzyme-added expansion of corn on starch structure and piglet growth,intestinal health and glycolipid metabolismThis study further explored the enzyme-added expansion of corn on the molecular structure characteristics of starch and its regulation on piglet growth,intestinal health and glycolipid metabolism.Corn was expanded(the same as in Exp.1)or expanded with enzyme(adding 4 g/kg of thermo-stable α-amylase before expansion).60 twentytwo-d-old weaning piglets(Duroc × Landrace × Yorkshire)with initial body weight of6.33 ± 0.14 kg were randomly assigned to 1 of 2 dietary treatments with 5 replicates per treatment and 6 pigs per replicate: 1)EP(Expansion),2)EEP(Enzyme-added expansion).This study lasted 26 days.Results showed as follows:(1)Compared with native corn starch,the average particle size of EP and EEP starch particles increased by 45% and 42%,respectively,the characteristic diffraction peaks of starch A-type crystals disappeared at the diffraction angle 2θ of 18° and 23°.The molecular weight of amylopectin decreased by 62% and 60% respectively,and the molecular weight of amylose decreased by 95%.Compared with the EP group,the proportion of short chains(DP < 13)in EEP starch molecules increased by 36%,and the content of small molecular sugars increased by 109%;the peak,trough and final viscosity of EEP starch decreased by 70%,89% and 94%,respectively,and the disintegration value and regeneration value were reduced by 44% and 98% respectively;(2)EEP improved F/G,and decreased the diarrhea index of weaning piglets(P <0.05);(3)EEP increased the apparent total tract digestibility(ATTD)of ash,calcium and phosphorus(P < 0.05),and tended to increase the ATTD of dry matter(P = 0.069).Moreover,EEP increased jejunal trypsin,α-amylase,lipase,sucrase and maltase activities,and jejunal expression of SGLT-1,GLUT-2,EGF,and Claudin-1 genes of weaning piglets(P < 0.05).(4)EEP decreased the content of valeric and butyric acid in cecal and butyric acid in colonic digesta of weaning piglets(P < 0.05),and increased the content of cecal acetic acid of weaning piglets(P < 0.05).16 S sequencing analysis showed that no significant difference in α-diversity index of colonic microorganisms(P > 0.05),and further LEf Se analysis showed that the species with significant difference in EEP group was Parabacteroides(P < 0.05).(5)EEP tended to lower postprandial insulin levels in weaning piglets(P = 0.086).Moreover,EEP increased longissimus dorsi muscle fiber area in weaning piglets(P <0.05)and tended to increase longissimus dorsi muscle fiber diameter in piglets(P =0.067).In addition,EEP increased the expression of AMPK、CPT1 and SLC2α gene in the liver(P < 0.05).EEP decreased the expression of insulin pathway related genes INSR、IRS1 and PIK3,fat transportation related genes FAT/CD36,as well as fat synthesis related genes FAS in the muscle(P > 0.05).Moreover,EEP increased CPT1 and GSK3β expression in the muscle(P < 0.05).These results indicated that the expansion of corn combined with enzymatic hydrolysis can further promote the degradation of starch molecular structure,which contributed to the digestion and utilization of weaning piglets.The expansion of corn starch combined with in vitro enzymatic hydrolysis can improve the intestinal digestion and barrier function of weaning piglets,regulating the structure and metabolite composition of hindgut microbiota,and improving the glucose utilization efficiency and promoting the growth of muscle fibers.Exp.3 Effects of corn expansion moisture on starch structure and piglet growth,intestinal health and glycolipid metabolismThe results of Exp.2 showed that the expansion and enzymatic hydrolysis of corn starch had a synergistic pre-digestion effect,thus the purpose of this experiment was to compare the effects of amylase under different moisture during corn expansion on starch structure,and piglet growth,intestinal health and glycolipid metabolism.A 2-factor design was used in the experiment.48 twenty-two-d-old weaning piglets(Duroc× Landrace × Yorkshire)with initial body weight of 6.76 ± 0.15 kg were randomly assigned to 1 of 4 dietary treatments with 6 replicates per treatment and 2 pigs per replicate: 1)LM-EP(adding 7.5 % moisture before corn expansion),2)HM-EP(adding15 % moisture before corn expansion),3)LM-EEP(adding 7.5 % moisture and 4 g/kgα-amylase before corn expansion),and 4)HM-EEP(adding 15 % moisture and 4 g/kgα-amylase before corn expansion).This study lasted 14 days.This study was conducted to investigate the effects of enzyme-added expansion under different moisture conditions on molecular structure and gelatinization characteristics of corn starch and growth performance,intestinal health,and glucose-lipid metabolism of weaning piglets.Results showed as follows:(1)HM-EP and HM-EEP reduce the diffraction peak intensity at the diffraction angle 2θ of 20°.In LM-EEP and HM-EEP groups,the proportion of short starch chains(DP < 13)increased by 60%,the content of small molecular sugar increased by 197%,and the peak,trough and final viscosity of starch decreased by 60%,87% and 85%,respectively.and regeneration value decreased by 54% and 81% respectively;(2)Enzyme-added expansion significantly increased ADG(P < 0.05),and tended to increased ADG of weaning piglets(0.05 < P < 0.10).(3)Enzyme-added expansion significantly increased the duodenal villus height,jejunal villus height and villus height to crypt depth ratio,ileal villus height and villus height to crypt depth ratio,ATTD of dry matter,crude protein,gross energy,crude fat,ash,calcium and phosphorus,jejunal trypsin,α-amylase,lipase,sucrase,maltase,γ-glutamine transferase and alkaline phosphatase activities,jejunal expressions of SGLT-1,GLUT-2,ZO-1,and Occludin genes of weaning piglets(P < 0.05),and decreased serum DAO and D-lactic acid content of weaning piglets(P < 0.05).(4)16S high-throughput sequencing analysis showed that moisture and amylase had no significant effect on α-diversity index in the colonic microorganisms of weaning piglets(P < 0.05).In addition,enzyme-added expansion decreased the contents of isobutyric acid in cecum,acetic acid and isobutyric acid in colon of weaning piglets(P< 0.05),while HM-EP and HM-EEP decreased cecal valeric acid,colonic butyric acid and valeric acid of weaning piglets(P < 0.05).(5)Enzyme-added expansion decreased the content of serum adiponectin and insulin of weaning piglets(P < 0.05),and increased the diameter and area of longissimus dorsi muscle of weaning piglets(P < 0.05).In addition,enzyme-added expansion increased liver AMPK,HSL,LPL,SLC2α,and PCK1 genes expressions(P< 0.05),and decreased SREBP-c and ACC genes expressions(P < 0.05).Moreover,enzyme-added expansion increased AMPK,LPL,CPT1,SLC2α,GSK3β,and PCK1 genes expressions of longissimus dorsi muscle(P < 0.05),and decreased GYS gene expression of longissimus dorsi muscle(P < 0.05).HM-EP and HM-EEP decreased the content of serum insulin(P < 0.05),and decreased liver PCK1,HSL and longissimus dorsi muscle PCK1 gene expression(P < 0.05).These results indicated that increasing the moisture content from 7.5% to 15% did not improve the effect of corn enzyme-added expansion,and 7.5% moisture content can meet the moisture conditions required for enzyme-added expansion.In the process of enzyme-added expansion,enzymatic hydrolysis is the main factor that promotes the degradation of starch into short chains(DP<13)and small molecular sugars,and further improved growth performance,intestinal health,glucose utilization and growth of muscle fibers of piglets.Exp.4 Effects of amylase supplementation in expanded corn diets on growth performance,nutrient digestibility,and serum biochemical parameters of weaning pigletsThe purpose of this experiment is to further determine the effect of enzyme-added expansion of corn and dietary supplementation of combined amylase(glycosylase and pullulanase)with exosection and debranching activities through a large-scale animal experiment.A 2-factor design was used in the 14-d animal experiment.240 twentyeight-d-old weaning piglets(Duroc × Landrace × Yorkshire)with initial body weight of 7.98 ± 0.17 kg were randomly assigned to 1 of 4 dietary treatments with 6 replicates per treatment and 10 pigs per replicate: 1)EP: expansion,2)EP-AM: expansion supplemented with combined amylases,3)EEP: enzyme-added expansion,and 4)EEPAM: enzyme-added expansion supplemented with combined amylases.This study was conducted to investigate the effects of enzyme-added expanded corn and supplementation of combined amylase in diet on growth performance,nutrient digestibility and serum biochemical parameters of weaning piglets.The results showed that:(1)Enzyme-added expansion increased feed intake and ADG of weaning piglets(P < 0.05).However,supplementation of combined amylase in the diet did not improve growth performance of weaning piglets(P > 0.05).(2)Enzyme-added expansion increased the ATTD of dry matter,crude protein,gross energy,and crude fat of weaning piglets(P < 0.05).Supplementation of combined amylase had no significant effect on the ATTD of nutrients in piglets(P > 0.05).(3)The content of DAO and D-lactic acid in serum of weaning piglets were reduced by enzyme-added expansion(P < 0.05).Supplementation of combined amylase had no significant effect on the activity of DAO and content of D-lactic acid in serum of weaning piglets(P > 0.05).(4)Enzyme-added expansion had no significant effect on fasting blood glucose value of weaning piglets(P > 0.05).However,supplementation of combined amylase increased the fasting blood glucose level of weaning piglets(P < 0.05),and there was a significant interactive effect on the fasting blood glucose level between enzyme-added expansion and combined amylase supplementation(P < 0.05).In conclusion,enzyme-added expansion significantly improved the growth performance and nutrient digestibility of weaning piglets.Supplemented with amylase increased the fasting blood glucose level of piglets,but had no significant effect on growth performance and nutrient digestibility of weaning piglets.Collectively,the conclusions of this thesis were as follows:Enzyme-added expansion(adding 4 g/kg thermo-stable α-amylase and 7.5%moisture,and expanded at 105℃)significantly change the corn starch molecule structure: the particle size of starch particles increased,the crystal structure was destroyed,the molecular weight decreased,the chain length shortened,the content of oligosaccharides increased,and the viscosity and retrogradation value decreased.Feeding enzyme-added expanded corn improves the growth performance and intestinal health related parameters,and regulates the glucose-lipid metabolism through the AMPK and insulin pathways,and promotes muscle fibers growth of weaning piglets.Supplementation of exogenous amylase to the enzyme-added expanded corn diet did not further improve growth performance and intestinal health.