| This experiment systematically studied the regulation of oregano EO on the development of the gastrointestinal tract of lambs through three aspects: the morphology structure,function and microorganisms of gastrointestinal.Firstly,the effects of OEO on nutrient digestion and metabolism,blood biochemistry and immune indexes of lambs were studied through feeding experiment.Furthermore,the effects of OEO on the gastrointestinal morphology of lambs was studied.On this basis,through the detection of gastrointestinal fermentation parameters and digestive enzyme activity,to reveal the differences among different levels of OEO on the gastrointestinal structure and function of lambs.Finally,the microbiota of rumen,cecum and rectal was determined to reveal the effects of inclusion rate of OEO on the microbial structure of the gastrointestinal tract of lambs.In this study,the effects of inclusion rate of OEO on nutrient digestion and metabolism,blood biochemistry,gastrointestinal development,fermentation,digestive enzymes and microbiota of lambs were studied.The results are as follows:Trail one: the effects of OEO on nutrient digestion,blood biochemical and immune indexes of lambs..18 healthy crossbred male lambs(Suffolk × Small tail Han sheep)with similar body weight were selected.A single factor experiment design was adopted in the experiment.All lambs were divided into 3 groups.Each group had 6 lambs.Lambs in the control group(CON)were fed a basic diet,and lambs in the experiment groups were fed the basic diet supplemented with 4 g/d(EO4)or 7 g/d(EO7)oregano EO.The ratio of concentration and forage was 45:55.The experiment lasted for 82 days,including 10 days of preliminary trial and 72 days of trial.The results showed that: 1)the apparent digestibility of DM and CP increased with the inclusion rate of OEO(P>0.05).Compared with the control group,the apparent digestibility of CP in OEO groups significantly increased(P<0.05).2)the concentration of blood TP,CAT,Ig G and Ig M increased with the addition of OEO(P<0.05),and the concentration of blood TG,CH and LDH significantly reduced(P<0.05).Compared with the control group,the blood ALB and SOD concentrations in EO4 group were significantly increased by 7.73 g/L and 6.5 ng/m L respectively(P<0.05),while the GLU concentration in EO7 group was significantly increased by 0.46 mmol/L(P<0.05).Trail two: the effects of OEO on morphological structure of the gastrointestinal tract of lambs.The results showed that: 1)dietary addition of OEO significantly increased the reticulum weight of lambs(P<0.05).The volume of reticulum and rumen in EO7 group significantly higher than those in control group(P<0.05),and the relative volume of abomasum in EO7 group was the lowest(P<0.05).The weight of intestinal and small intestinal increased with the inclusion rate of OEO(P>0.05).The relative weight of ileum in EO7 group was significantly lower than that in the other two groups(P<0.05),and the relative weight of rectum was significantly higher than that in the other two groups(P<0.05).2)the papilla height and cuticle thickness of rumen in EO7 group were significantly higher than control group(P<0.05).Compared with the control group,the primary plica height and muscle thickness of reticulum were significantly increased(P<0.05).The villus height,muscular thickness of duoderum,the V/C value,villus height and muscular thickness of ileum,and the V/C value of jejunum increased with the addition of OEO,and significantly higher than those in the control group(P<0.05).Diet addition of OEO significantly reduced the crypt depth of duodenum and jejunum,and the villus width of ileum(P<0.05).Diet addition of 7 g/d OEO significantly increased the villus width of duodenum and the villus height of jejunum(P<0.05).Dietary addition of OEO significantly increased the mucosal layer and muscle thickness of rectal(P<0.05),which was the highest in the EO4 group.Trail three: the effects of OEO on gastrointestinal track enzyme activities of lambs.The results showed that: 1)diet addition of OEO significantly increased the activity of cellulase in rumen,reticulum and omasum(P<0.05),and diet addition of 7 g/d OEO increased the activity of β-glucosidase in rumen and reticulum(P<0.05).Diet addition of 4 g/d OEO increased the activity of β-glucosidase in the omasum(P<0.05).The α-amylase activity in rumen increased significantly with diet addition of OEO(P<0.05),and diet addition of 7 g/d OEO increased the amylase activity in reticulum,the lipase activity in rumen and the pepsase activity in abomasum(P<0.05).The pepsase activity in rumen was increased with addition of 4 g/d OEO(P<0.05).2)The activity of α-amylase and trypsase of pancreas in the EO7 group were significantly increased by 5.11 U/g(P<0.05)and 2.33 U/g(P<0.05),respectively.The lipase and α-amylase of duodenum in EO7 group was increased by 0.51 U/g and 0.82 U/g,respectively.The lipase and α-amylase activity in jejunum was improved with addition OEO(P<0.05).In addition,the activity of trypsase and chymotrypsin of jejunum in EO7 group was increased by 1.2 U/mg and 0.95 U/mg,respectively(P<0.05).The activity of α-amylase of ileum in EO7 group was increased significantly.The activity of cellulase and β-glucosidase of cecum in EO7 group was increased by 15.30 U/g and 0.87 U/g,respectively(P<0.05).The activity of α-amylase,cellulase and β-glucosidase of colon in EO7 group was increased by 0.43 U/g(P<0.05),8.37 U/g(P<0.05),and 0.82 U/g(P<0.05).Trail four: the effects of oregano EO on the gastrointestinal tract fermentation parameters of lamb.After slaughtered the lambs in trail one,gastrointestinal contents of lambs were collected and p H,NH3-N and VFAs were detected.The results showed that: 1)the p H values were maintained in normal scope and diet addition of OEO had no significant effect on the gastrointestinal p H of lambs(P>0.05).Diet addition of OEO significantly increased the propionate concentration of reticulum(P<0.05),compared with the control group,the propionate concentration and percentage of rumen and omasum in the EO7 group significantly improved(P<0.05),however the NH3-N and butyrate concentration,A/P values,butyrate and valerate percentage of rumen,the percentage of valerate and isovalerate of reticulum in EO7 group were significantly decreased(P<0.05).OEO had no significant effect on the fermentation parameters of abomasum(P>0.05).2)diet addition of OEO had no significant effect on the fermentation parameters of small intestine(P>0.05).3)compared with the control group,the concentration of TVFA and acetate of caecum in EO7 group was significantly increased,and the concentration of NH3-N,valerate and isovalerate,the percentage of butyrate,valerate and isovalerate of caecum in EO7 group were significantly decreased(P<0.05).Diet addition of OEO significantly increased the concentration of propionate and valerate,and the percentage of valerate in colon(P<0.05),significantly reduced the percentage of isobutyrate in colon(P<0.05).Compared with the control group,the butyrate concentration and percentage of rectum in EO4 group were significantly increased(P<0.05),the concentration of butyrate and isobutyrate were significantly increased in EO7 group(P<0.05).Trail five: the effects of OEO on the bacterial structure and composition of rumen,cecum and rectum mirobiota of lambs.The results showed that: 1)OEO improved the OTUs numbers(P<0.05)and Chao1 index(P<0.05).2)dietary addition of oregano EO increased Bacteroidetes abundance in the rumen(P<0.05)and decreased Firmicutes,Protebacteria,Elusimicrobia and Chloroflexi abundance(P<0.05).OEO had no significant effect on the dominant phylums of caecum and rectum(P>0.05),but had a significant effect on the low-abundance phylums(P<0.05).OEO significantly increased the abundance of rumen Prevotellaceae,and Rikenellaceae(P<0.05),and reduced rumen Lachnospiraceae,Christensenellaceae,Eubacteriaceae,Clostridiaceae and Succinivibrionaceae abundance(P<0.05).Compared with the control group,Porphyromonadaceae abundance of rumen in EO4 group was significantly increased,and Veillonellaceae and other families in EO7 group was significantly increased,while Oscillospiraceae,Erysipelotrichaceae and Spirochaetaceae abundance in EO7 group was significantly decreased.OEO increased the abundance of Christensenellaceae,Eubacteriaceae and Clostridiaceae in the rectum(P<0.05).OEO significantly reduced the abundance of Bacteroidacea,Lachnospiraceae and Spirochaetaceae in caecum and rectum(P<0.05).Compared with the control group,Ruminococcaceae abundance of caecum and rectum in EO4 group was significantly increased,and Porphyromonadaceae abundance was significantly decreased.The abundance of Prevotellaceae in EO7 group was significantly increased,and Veillonellaceae was significantly decreased.(P<0.05).3)OEO increased the abundance of Prevotella and decreased the abundance of Eubacterium,Paraprevotella and Christensenella(P<0.05).Compared with the control group,the abundance of Rikenella in EO4 group was significantly decreased,and the abundance of Clostridium was significantly decreased.Paraprevotella abundance in EO7 group was significantly increased.Compared with the control group,Porphyromonadaceae_unclassified abundance in EO4 group was significantly decreased,and Paraprevotella abundance in EO7 group was significantly increased.Lachnospiraceae_unclassified and Saccharofermentans significantly decreased.OEO increased the abundance of rectum Clostridium,Eubacterium and Christensenella(P<0.05),and decreased the abundance of rectum Roseburia and Treponema(P<0.05).Compared with the control group,Ruminococcus and Saccharofermentan abundances in EO4 group increased significantly(P<0.05),and Paraprevotella abundance significantly increased in EO7 group(P<0.05)and Prevotella abundance in EO7 group significantly decreased(P<0.05).Overall,diet add a moderate amount of OEO have regulation effect to sheep rumen fermentation,can reduce the NH3-N concentration of rumen,and can improve the apparent digestibility of CP,promote the morphological structure development of gastrointestinal,on of the lamb and the improve the antioxidant capacity and immune function of lambs,change the microbiota structure of the gastrointestinal tract.After comprehensive consideration,7 g/d is the appropriate dietary addition of OEO under the conditions of this experiment. |
