Effects Of Different Amylose/Amylopectin Ratio On The Development Of Gastrointestinal Tract And MRNA Expression Of Related Genes In Fattening Lamb

A scientific research was conducted to evaluate effects of different ratios ofsupplemental dietary amylose/amylopectin on gastrointestinal of fattening lambs.Base on the comparison of difference of gastrointestinal tract morphology andfunction by feeding different ratios of supplemental dietary amylose and amylopectin,the mRNA expression of growth-relate genes in the small intestinal mucosa offattening lambs were futher studied in order to analysis the reasons of the differentstimulate of amylose/amylopectin ratio on the gastrointestinal tract development.A total of thirty-six male lambs were selected, and randomly assigned to fourdietary treatments. All lambs were free to diets and water. Tapioca starch (TS), peastarch (PS), maize starch (MS) and wheat starch (WS) were used as the sole dietaryenergy source. All diets were feed to fattening lambs for56days. At d21、35、and56of age,30min before morning feeding fortnightly, fattening lambs blood sampleswere taken and serum was collected. The fattening lambs were slaughtered on the lastday of the feeding experiment. Sections of rumen and intestine，intestinal chime, andmucosa of small intestine were collected. The results were showed as following:(1) Effects of dietary amylose/amylopectin ratio on the gastrointestinal tractmorphology development of fattening lambsWhen feeding with PS diet which amylose/amylopectin ratio was0.48, papillaelength, the surface of papillae, and papillae concentration in fattening lambs were thegreatest among the four treatments (P<0.05). PS significantly increased the villusheight, villus surface and crypt depth compare to other three treatment in duodenum(P<0.05). Furthermore, in jejunum, PS significantly increased the crypt depth andvillus surface. However, TS significantly increased the crypt depth, significantlydecreased villus: crypt and villus surface in ileum (P<0.05).(2) Effects of dietary amylose/amylopectin ratio on blood parameters and digestiveenzyme of the small intestine in fattening lambs At d56, PS significantly increased blood cholesterol concentration in fatteninglambs (P<0.05). What′s more, PS increased blood lactate dehydrogenase (LDH)extremely significant at d21, d35and d56(P<0.01). Blood growth hormone (GH) andBHBA concentration were greater in fattening lambs provided PS diet withamylose/amylopectin ratio was0.48(P<0.05), however, PS significantly decreasedblood insulin concentration in fattening lambs (P<0.05). The results show that theactivity of amylose in the digesta and mucous in small intestine was extremelysignificantly high in the PS treatment (P<0.01). In the mucous of duodenum andileum, the activity of maltase also significantly high in PS treatment (P<0.05), lactasewas also increased in some parts.(3) Effects of dietary amylose/amylopectin ratio on mRNA expression of IGF-1、IGF-1R and SGLT-1、GLUT-2related genesIGF-1and IGF-1R expression were greater in fattening lambs provided PS dietwith amylose/amylopectin ratio was the highest as0.48(P<0.05). The dietaryamylose/amylopectin ratio in TS was the lowest among the treatments, IGF-1Rexpression was also the lowest. The mRNA expression of GLUT-2and SGLT-1weregreater in fattening lambs provided PS diet (P<0.05).The above results proved that in fattening lambs provided PS diet withamylose/amylopectin ratio was the highest as0.48was best for gastrointestinal tractmorphology and would increase the activity of digeative enzyme in fattening lambs.The mRNA expression of growth-relate genes were greater in fattening lambsprovided PS diet, which means PS could promote the up-growth of gastrointestinaltract.