Effects Of Different Starch Sources On Intestinal Development,Digestive Enzyme Activities And Related Gene Expression In Lambs

The effects of different starch sources on small intestine development,fermentation,digestive enzyme activity,small intestine development related genes and glucose transporter protein gene m RNA of lambs of different ages were determined systematically in this study.A completely randomized trial was designed,starch source and lamb day-old were used as the experimental factors.Forty-eight male lambs(Northeast fine wool sheep×Small-tailed Han sheep)were randomly divided into 4 groups with 3 replicates in each group and 4 lambs per replica.The tapioca starch,corn starch,wheat starch and pea starch were selected as the sole source of starch in lamb concentrate.The whole experiment lasted for 77 days,at the 21 st,35th,56 th and 77 th days,one lamb was slaughtered for each repetition,the relative mass of each intestinal segment,the morphology of the small intestine,the volatile fatty acids in the intestinal chime,the digestive enzyme activity of the small intestine,the expression of small intestine development related genes and glucose transporter gene m RNA were measured.The results are as follows:(1)Effect of different starch sources on the relative mass of the intestinal segments and the morphology and structure of small intestine in lambs.The relative mass of each intestinal segment of lamb was not significantly affected by different starch sources in this test(% live weight,% intestinal weight)(P>0.05).Compared with tapioca,corn and wheat starch group,the height of duodenum and jejunum villi of lambs in pea starch group was highest(P<0.05),while the width of jejunum and ileum villus of lambs in pea starch group was widest(P<0.05),and the depth of recess and the surface area of small intestine of lambs in the pea starch group were largest(P<0.05).In addition to the relative mass of the rectum(% live weight),the relative mass of the small intestine,the jejunum,the large intestine and rectum(% intestinal weight),the villi width and the crypt depth of duodenum of the lamb had no significant influence(P<0.05),the growing period had significant influence on the other indexes(P<0.05).(2)Effects of different starch sources on volatile fatty acids in small intestinal chyme of LambsThe concentration of acetic acid and isobutyric acid in duodenum,chyme aceticacid/propionic acid in jejunum and ileum were not significantly affected by different starch sources in the concentrate(P>0.05).Compared with the other three starch groups,the concentration of propionic acid and acetic acid/propionic acid in duodenum of 35 days old lambs in pea starch group was highest(P<0.05),and the concentration of acetic acid in ileum and jejunum chyme isobutyric acid of 77 days old lambs in pea starch group were highest(P<0.05),the concentration of butyric acid in jejunum and ileum was highest(P<0.05).The growth period had no significant effect on the concentration of chyloacetic acid in the jejunum of lambs,but had a significant effect on the other indexes(P<0.05).(3)Effect of different starch sources on intestinal digestive enzyme activity of lambsThere were no significant effects of different starch sources on the activity of maltase in ileum of lambs,trypsin activity in duodenum and ileum and chymotrypsin activity in duodenum(P>0.05).Compared with tapioca,corn and wheat starch groups,the amylase and lactase activities in duodenum of lambs in pea starch group were the highest(P<0.05),the activity of amylase,maltase,lactase,trypsin and chymotrypsin in jejunum of lambs in pea starch group was the highest(P<0.05),and the activity of amylase and chymotrypsin in the ileum of lambs in pea starch group was the highest(P<0.05).The activities of digestive enzymes in the small intestine of lambs were significantly affected by the growth period(P<0.05),except that the activity of lactase in the small intestine decreased with the increase of the growth period,and the other activities increased with the increase of the growth period(P<0.05).(4)Regulation of m RNA expression of small intestine development related genes and glucose transport carrier protein genes in lambs by different starch sourcesThere was no significant effect on the expression of IGF-1 and IGF-1R m RNA in jejunum of lamb with different starch sources(P>0.05).Compared with the other three starch groups,the expression of IGF-1,IGF-1R m RNA in duodenum and ileum and the expressions of EGF,SGLT-1 and GLUT-2 m RNA in small intestine of lambs were significantly increased by pea starch(P<0.05).In addition to having no significant effect on the expression of GLUT-2 m RNA in the ileum of lambs,the expression of IGF-1,IGF-1R,EGF,SGLT-1 and GLUT-2 m RNA in the small intestine of lambs was significantly affected by growth period(P<0.05).To sum up,the concentrate fed with different starch sources did not affect the relative quality of the intestinal segments of lambs,but compared with the other three starch diets,thediets of pea starch improved the morphology of intestinal tissues in lambs,promoted the production of butyric acid,the secretion of digestive enzymes and the up-regulation of genes associated with small intestine development and glucose transport carrier protein.It can be speculated that feeding pea starch diet can promote the development and function of small intestine in early stage of lamb.