The Study On Digestive Organs And Amylase Gene Polymorphism In 80～200 Days Old Lambs

In order to guide the sheep production, selection-breeding and utilization of sheep breeds resources in China, a systematic study was conducted on effects of sheep breeds and age on the development of digestive organs and digestive enzyme, also try to suggest the correlation between the amylase gene polymorphism of three sheep breeds and their amylase activity.A hundred and twenty lambs from three breeds(Small-tail Han sheep, Tan sheep and Mongolia sheep, each N=40) which weaned at 60 days old were selected and raised at the same conditions. The measurements of relevant digestive organs were obtained and detailed after the lambs were slaughtered at the age of 80, 120, 160 and 200 days old to compare the growth-development law of digestive organs. The DNA molecular marker technologies---- PCR-SSCP were applied to evaluate the effects of genotypes of the candidate gene on amylase activity in these three populations. The dissertation was described in the following 5 sections:1. Digestive organs developmentThe results showed that the sheep breeds and age had significant effects on body weight(BW), average daily gain(ADG) and relative growth rate(RGR) in lambs(P <0.05). Among these three sheep breeds, Small-tail Han sheep had the highest ADG and Mongolia sheep had the lowest, while Small-tail Han sheep had the highest RGR and Mongolia sheep had the lowest. The age had significant effect on the weight of stomach, liver and small intestine(P<0.05) and had no significant effect on the weight of pancreas.2. The digestive enzyme activityThere were no significant differences of pH value in bile, rumen, abomasum and jejunum from 80~200 days old, while the pH value of bile, jejunum and duodenum of Small-tail Han sheep and Tan sheep were significant higher than Mongolia sheep at the age of 200 days old; The amylase and lipase activity of pancreas in three sheep breeds reached the highest at the 160 days old then decreased, there were no significant differences among four stages in each sheep breed. At 200 days old, the amylase and trypsin activity of Small-tail Han sheep were significant higher than Tan sheep and Mongolia sheep.3. Based on the sequence of sheep amylase gene from GenBank, four primers(A1,A7,A8,A10) were designed and synthesized, which represented the exon1 and 5'UTR, exon7, exon8 and exon10, respectively. The results showed that three loci(A1,A7,A10)were demonstrated polymorphism in the four selected loci in tested sheep population. The genotypes were nominated AA, AB and BB. The genotype AA was wild type while the AB was heterozygote, the BB was mutation type.4. The sequences of three loci were analyzed usedλ-test. The results demonstrated that at the locus A1 the Small-tail Han sheep and Mongolia sheep were at the Hardy-Weinberg equilibrium; at the locus A7 the three sheep breeds were all at the Hardy-Weinberg equilibrium; at the locus A10 the Small-tail Han sheep was at the Hardy-Weinberg equilibrium. The (PIC) and Shannon's information index(S) of locus A7 and A10 in Mongolia sheep were greater than Small-tail Han sheep and Tan sheep, it suggested that the Mongolian sheep contained genetic diversity.5. The association of variations of AMY gene with amylase activity in these three populations was analyzed. The results were showed as following:In the Small-tailed Han sheep, The genotype of A7 was associated with amylase activity, and the relationship was significant(P<0.05). The least-squares analysis showed that the A7-AA was the highest and it can be used as a maker of the trait for Small-tailed Han sheep;In the Tan sheep, The genotype of A10 was associated with amylase activity, and the relationship was significant(P<0.05). The least-squares analysis showed that the A10-AA was the highest and it can be used as a maker of the trait for Tan sheep;In the Mongolia sheep, The genotype of A1 was associated with amylase activity, and the relationship was significant(P<0.05) The least-squares analysis showed that the A1-AA was the highest and it can be used as a maker of the trait for Mongolia sheep.