| Starch is a major component of carbohydrates in monogastric animal diets and an important source of energy,accounting for more than 50%of feed production costs and formula space.Starch is a mixture of amylose and amylopectin in certain proportions.Due to the differences in the chemical properties of amylose and amylopectin,the nutritional physiological effects and effective energy values of different starch structures on pigs are quite different.However,so far,the studies on starch have not been in-depth,and the differences in effective energy values have not been reported.Therefore,in this study,dietary amylose/amylopectin ratio was adjusted to investigate the nutritional physiological effects and energy value differences of different starch structures on pigs and the possible mechanisms.It provides the experimental basis for understanding the nutrition principle of starch and rational utilization of starch.Exp.1 Physiological and developmental patterns of carbohydrate utilization in pigletsThe experiment aims to explore the developmental patterns of carbohydrate digestion physiology in piglets with age.A total of 42 DLY piglets were selected and intestinal,pancreatic,and colonic chyme samples were collected at 0,7,14,21,28,35,and 42 d,respectively,to analyze intestinal morphology,pancreatic and intestinal digestive enzyme activities,short-chain fatty acid concentration,and microbial abundance in colonic chyme.The results show that:1)The villus height of duodenum and jejunum reached its maximum value at week 2(14 d)and week 1(7 d),respectively(P<0.01),while the villus height of ileum reached its maximum value at day 0 after birth.The ratio of villus height to crypt depth of duodenum at 14 d was significantly higher than that at other ages,while jejunum and ileum at 0 d were the maximum values(P<0.01).2)The activities of intestinal sucrase and maltase were increased with the increase of age at lactation stage(7-14 d)and nursery stage(28-42 d),but decreased at weaning stage(21 d)(P<0.05).The lactase activities at 0 and 7 d were significantly higher than those at other ages(P<0.01).The activities of pancreatic amylase increased with the age of piglets,while the activities of lipase and protease decreased gradually from birth to weaning(0-21d),and then increased at 28-42 d(P<0.05).3)The contents of acetic acid,propionic acid,butyric acid and total volatile fatty acid in colonic chyme increased with the increase of piglets age from 0 to 14 d,decreased at 21d,and then increased at 28 to 42 d(P<0.01).4)At the phylum level,the abundance of Firmicutes and Bacteroidetes was higher at42 d when the total SCFA concentration was higher than that at 0 d,while the abundance of Proteobacteria was lower,but the abundance of Proteobacteria in the colon increased at21-28 d(P<0.01).At the genus level,Escherichia＿Shigella had the highest abundance in0 and 21 d(P<0.05),while Lactobacillus had the highest abundance in 7-42 d(P<0.05).5)Lactobacillus、unclassified＿Ruminococcaceae and Faecalibacterium are positively correlated with amylase and SCFAs.unclassified＿Lachnospiraceae、unclassified＿Bacteroidetes and Roseburia are positively correlated with sucrase and maltase.Escherichia＿Shigella and Bifidobacterium were negatively correlated with amylase,sucrase and maltase.It can be seen that as piglets age,their digestive function can be enhanced by increasing the activity of digestive enzymes in the intestine and pancreas,as well as the abundance of carbohydrate decomposing bacteria in the intestine.However,weaning hinders the development of gut function and increases the abundance of harmful bacteria.Exp.2 Effects of Different Structure Starch on Growth Performance and Intestinal Health of Weaned PigletsExp.1 found that the intestinal morphology of piglets was damaged and their carbohydrate digestion function was weakened in the first week(28 d)after weaning.The aim of this experiment was to investigate the relationship between different structures of starch and the growth performance and intestinal health of piglets.A total of 108 DLY piglets weaned at 21 days of age with body weight(BW)of 7.51±0.05 kg were selected and randomly divided into 6 treatments according to the principle of BW and half male and half female.Each treatment had 6 replicates,and each replicate had 3 piglets.They were fed with basic diet and semi pure diet with starch amylose/amylopectin ratio(AR)of 2.90,1.46,0.68,0.31 and 0.14,respectively.The experiment lasted for 21 d.The results show that:1)Dietary starch structure had no significant effect on final weight,average daily gain,average feed intake and F/G of weaned piglets at 21 days of age(P>0.05).2)AR 0.68,0.31 and 0.14 groups increased the serum glucose concentration of piglets at post-prandial 3 and 5 h(P<0.01),and linearly and quadratically increased the glucose concentration of at post-prandial 4 h(P<0.05).Compared with AR 0.14 group,AR 2.90,1.46 and 0.68 groups quadratically increased the fasting and 1 h insulin concentration of piglets(P<0.01).Compared with AR 0.31 and 0.14 groups,AR 2.90,1.46 and 0.68groups increased the 1 h post-prandial insulin concentration(P<0.01).However,AR 0.14group increased the insulin concentration at post-prandial 2-5 h(P<0.01).In addition,postprandial changes in serum glucose and insulin concentrations in AR 0.14 group were greater than those in AR 2.90 group.Compared with AR 2.90 and 1.46 groups,the expression level of FAS in duodenum in AR 0.14 group was significantly increased(P<0.05).3)Compared with AR 2.90 group,AR 0.31 and 0.14 groups increased the activities of sucrase and maltase in jejunum and ileum of piglets(P<0.05).There were no significant differences in the activities of duodenal sucrase,maltase and lactase among different diets(P>0.05).Compared with other groups,AR 0.14 group improved the whole intestinal apparent nutrient digestibility of crude protein,crude fat,dry matter,energy and crude ash.4)Compared with the other four treatment groups,the CON and AR 2.90 groups had higher villus height,villus height crypt depth ratio,OCLN gene expression in the jejunum,and Bcl-2 gene expression in the duodenum and jejunum(P<0.05);Significantly reduced late stage and total cell apoptosis rates in the duodenum,jejunum,and ileum(P<0.05).These results indicate that high amylopectin can lead to stronger and faster serum glucose-insulin response and increase the expression of genes related to lipogenesis in weaned piglets.High amylose diet can promote intestinal health of piglets by improving intestinal morphology,barrier function and reducing the apoptosis rate of intestinal epithelial cells.Exp.3 Effects of corn with different starch structure on growth performance and glycolipid metabolism of pigsExp.2 used semi pure feed to study and found that different structures of starch have different nutritional and physiological effects.In this experiment,practical diets were used to further study the effects of different structure of starch on growth performance and glycolipid metabolism of pigs.A total of 72 DLY pigs with an initial BW of 8.47±0.38 kg were randomly divided into 2 groups based on the principle of similar BW and half male and half female,namely the ordinary corn group(amylose/amylopectin ratio:0.29)and waxy corn group(amylose/amylopectin ratio:0.07).The experiment lasted for 28 d.The results show that:1)Compared with the control group,the waxy corn group significantly increased the final weight,average daily gain and average daily feed intake of pigs(P<0.05),but there was no significant difference in F/G between the two groups(P>0.05).2)Compared with the control group,the waxy corn group significantly increased the contents of high density lipoprotein(HDL-C),free fatty acid(FFA),triglyceride(TG),total protein(TP)and urea nitrogen(BUN)in serum(P<0.05).However,dietary starch with different structures had no significant effects on serum albumin(ALB),aspartate aminotransferase(AST),alanine aminotransferase(ALT),glucose(GLU),low density lipoprotein(LDL-C),lactate dehydrogenase(LDH),total cholesterol(TC)and insulin(INS)(P>0.05).3)Compared with control group,waxy corn group increased the activity of glycogen synthetase(GCS)in liver and muscle,the content of glycogen in liver,the expression levels of SGLT-1 and GCS3βin jejunum(P<0.05),and decreased the expression level of G6PC in dorsal fat(P<0.05).4)Compared with the control group,waxy corn increased the content of fat,butyric acid,caproic acid,tetradecarbonate,cis-10-heptadecanoenoic acid,cis-9-octadecanoenoic acid,trans,trans-9,12-octadecanodienoic acid,cis,cis,cis,cis-9,12,15-octadecanotrienoic acid,23 carbonic acid in muscle,the activity of FAS in liver and muscle,FAS and ACC expression levels in liver and muscle(P<0.05);Decreased PPARα,ACOX1 in liver and ACOX1 in dorsal fat(P<0.05);The expression levels of MCT1 and FFAR2 in jejunum were increased(P<0.05).5)Compared with the control group,waxy corn increased the protein and energy content,muscle fiber diameter(P<0.05),and had a trend of reducing muscle fiber density(P=0.087)in the longissimus dorsi;Increased the content of aspartic acid,cysteine,valine,and isoleucine in muscles,the expression levels of GA in liver,muscle GDH,jejunum SLC1A1,SLC6A19,and SLC7A9(P<0.05),while decreased the expression levels of My HCII and My HCIIb in muscles(P<0.05).These results indicate that waxy corn can increase the deposition of fat and protein in pig muscle,promote the metabolism of glycollipids and nitrogen in liver and muscle,as well as the utilization of amino acids in intestinal tract to improve growth performance,and improve meat quality to a certain extent.Exp.4 Effects of starch with different structure on energy metabolism and available energy of pigsThe purpose of this study was to investigate the effects of different starch structures on energy utilization of pigs on the basis of Exp.3,to determine the net energy(NE)values of different starch structures in diets by comparative slaughter method,and to establish a prediction equation to estimate the NE values of different starch structures in diets.A total of 56 barrows weaned at 21 days of age with an initial BW of 10.18±0.11 kg were randomly divided into divided into 7 treatments with 8 replicates per treatment and 1pig per replicate.At the beginning of the formal trial,one group was randomly selected as the initial slauhhter group(ISG)and the other as the experimental group.The experiment lasted for 28 d.The results show that:1)Compared with high-amylose(AM)group(AR 3.09 and 1.47),high amylose(AP)group(AR 0.15)significantly increased the final body weight,average daily gain and average daily feed intake of pigs(quadratic,P<0.01),but the F/G of high amylopectin(AR 3.09)group was lower than that of control group and high amylose group(AR 0.15and 0.12)(P<0.05).2)Compared with the control group and the high amylose group(AR 3.09),the high amylopectin group(AR 0.15 and 0.12)had higher nutrient digestibility of dry matter,crude protein,energy and crude ash(P<0.01).3)Compared with the other 5 groups,AR 0.15 group had higher NE intake of 64Mcal,while AR 3.09 group had the lowest NE intake of 58 Mcal(P<0.05).In addition,the NE of retention(RE)gradually increased with the increase of dietary amylopectin content and the RE of the feed with AR 0.15 was 185kcal/kg higher than that with AR 3.09(P<0.05).The regression equation predicted by starch structure was RE of the diet=1235.243-48.298AM/AP(R~2=0.657,P=0.05).The results indicated that high amylopectin diet could improve the NE of deposition and growth performance by increasing nutrient digestibility and fat deposition.In conclusion,the digestive function of piglets is gradually enhanced with the increase of age,but weaning seriously affects the intestinal development of piglets,and the digestive function begins to recover gradually at 35-42 d.Therefore,we subsequently studied the nutritional physiological effects of different starch structures on weaned piglets and pigs in the later stage of conservation.It was found that high amylose diet can promote intestinal health of weaned piglets by improving intestinal morphology and barrier function and reducing the apoptosis rate of intestinal epithelial cells,and high amylopectin can lead to stronger and faster serum glucose-insulin response.And increased the expression of genes associated with lipogenesis.Finally,the energy values of different starch structures were quantified by comparative slaughter method.It was found that high amylopectin could improve the growth performance of pigs in the late conservation period by increasing the deposition of body fat and deposition energy. |
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