| The purpose of this experiment is to study the in vitro antibacterial effect of oregano extract and its influence on the growth performance and intestinal barrier function of yellow feather broilers.In the in vitro experiment,the main components of oregano extract were thymol and carvacrol as the research objects to explore their effects on avian pathogenic Escherichia coli O78 and Salmonella pullorum.In the animal experiment,720 one-day-old fast Yellow-Feathered broiler male chicks with healthy and consistent weights were selected and randomly divided into 4 treatment groups according to the single-factor experiment design,with 6 replicates in each group,and 30 chickens in each replicate: CON group(Basic diet),OE200 group(basic diet 200 mg/kg oregano extract),OE400 group(basic diet 400mg/kg oregano extract),OE600 group(basic diet 600 mg/kg oregano Extract),the test period is 48 days.The in vitro test results showed that:(1)The minimum inhibitory concentration(MIC)of thymol against avian pathogenic Escherichia coli O78 and Salmonella pullorum were both 0.25 mg/m L;carvacrol against avian pathogenic Escherichia coli O78 and chicken The MIC of Salmonella pullorum is 0.5 mg/m L.(2)Thymol or carvacrol with sub-MIC concentration can inhibit the growth of avian pathogenic Escherichia coli O78 and Salmonella pullorum,delaying the time for the two bacteria to enter the exponential phase,slow growth and low number of viable bacteria in the stable phase In normal culture.(3)Thymol or carvacrol can inhibit the formation of avian pathogenic Escherichia coli O78 and Salmonella pullorum.(4)Thymol or carvacrol can inhibit the motility of avian pathogenic Escherichia coli O78 and Salmonella pullorum.(5)After treatment with thymol or carvacrol,the total nucleic acid leakage of avian pathogenic Escherichia coli O78 and Salmonella pullorum increased.The results of animal experiments showed:(1)Growth performance: In the early stage of the experiment,compared with the control group,the average daily feed intake(ADFI)and average daily gain(ADG)of the experimental group showed a linear and quadratic increase significantly(P <0.05).In the middle of the experiment,the ADFI of the OE200 group was significantly lower than that of the control group(P<0.05);the ADG of the OE400 group was significantly higher than that of the other groups(P<0.05);the feed-to-weight ratio(F/G)of the experimental group was significantly reduced twice.At the end of the experiment,the ADFI of the OE200 and OE600 groups was significantly lower than that of the control group.During the whole trial period,the ADG of the OE200 group and the OE400 group was significantly higher than that of the control group;the F/G of the experimental group decreased significantly in linear and quadratic ways.(2)Serum biochemical indicators: At 21 days of age,the serum aspartate aminotransferase(AST)activity of the OE600 group was significantly lower than that of the control group(P<0.05);the serum total cholesterol(TC)content of the OE600 group was significantly lower than that of the control group(P<0.05);adding different doses of oregano extract has an effect on total blood protein(TP),alanine aminotransferase(ALT),triglycerides(TG),high-density lipoprotein cholesterol(HDL-C)and low levels of broilers in each group.There was no significant difference in density lipoprotein cholesterol(LDL-C)levels(P>0.05).At the age of 48 days,compared with the control group,the serum TP content of the test group showed a significant increase in linear and quadratic curves(P<0.05);the activity of AST in the test group showed a linear and significant increase(P<0.05);add There was no significant difference in serum ALT,TC,TC,HDL-C and LDL-C levels of different doses of oregano extract in each group of broilers(P>0.05).(3)Digestive enzyme activity: the 21 d jejunal amylase activity of the OE400 and OE600 groups was significantly higher than that of the control group(P<0.05),and the 21 d jejunal amylase activity of the OE200 group was significantly lower than the other groups(P<0.05);the test group The 21 d jejunal lipase activity was linearly significantly reduced(P<0.05);the 21 d chymotrypsin activity of the OE200 and OE600 groups was significantly higher than that of the control group(P<0.05).(4)Antioxidant performance of jejunal mucosa: At the 21 st day of age,the total antioxidant capacity(T-AOC)of the jejunal mucosa in the OE600 group was significantly higher than that of the control group(P<0.05);the jejunal mucosa was superoxidized in the OE400 and OE600 groups The activity of biodismutase(SOD)was significantly higher than that of the control group(P<0.05);the catalase(CAT)activity of the jejunal mucosa in the OE400 and OE600 groups was significantly higher than that of the control group(P<0.05);the jejunal mucosa of the OE400 group The content of malondialdehyde(MDA)was significantly higher than that of the control group and the OE200 group(P<0.05).At the 48 th day of age,there was no significant difference in the T-AOC of the jejunal mucosa of the groups(P>0.05);the SOD activity of the jejunal mucosa of the OE600 group was significantly higher than that of the control group(P<0.05);the CAT activity of the jejunal mucosa of the test group was secondary The curve was significantly reduced(P<0.05);the MDA content of jejunum mucosa in the OE600 and OE400 groups was significantly higher than that in the control and OE200 groups(P<0.05).(5)Intestinal permeability: at the 21 st day of age,the serum diamine oxidase(DAO)content of the OE600 group was significantly lower than other groups(P<0.05);at the 48 th day of age,the serum DAO content of the OE600 group Significantly lower than other groups(P<0.05),the serum DAO content of OE400 and OE600 groups was significantly higher than that of the control group(P<0.05).(6)Intestinal morphology: At the 21st day of age,the height of jejunal villi in the OE400 group was significantly higher than that of the control and OE600 groups(P<0.05);the jejunal crypt depth of the OE200 and OE400 groups was significantly lower than that of the control(P<0.05)The cashmere to hidden ratio of OE200 group and OE400 group was significantly higher than that of the control group(P<0.05).At the 48th day of age,compared with the control group,the jejunal villi height of the experimental group was significantly reduced in a quadratic curve(P < 0.05),and the jejunal villi height of the OE400 group was significantly higher than that of the OE200 and OE600 groups(P<0.05);The jejunal crypt depth of the OE400 group and the OE600 group was lower than that of the control group and the OE200 group(P < 0.05),and the jejunal crypt depth of the OE400 group was significantly lower than that of the OE600 group(P<0.05);the velvet-to-crypto ratio of the OE400 group was significantly higher In other groups(P<0.05),the cashmere-to-crypto ratio of the OE200 group was significantly lower than that of the control group and the OE600group(P<0.05).(7)Intestinal tight junction protein: At the 21 st day of age,the expression of ZO-1 and Claudin-1 in the jejunum of the experimental group showed a significant increase in the quadratic curve(P<0.05);the expression of Occludin in the OE200 group was significantly higher than Control group and OE600 group(P<0.05).At the 48 th day of age,the expression of ZO-1 and Occludin in the jejunum of the experiment showed a quadratic curve and significantly decreased(P<0.05);the expression of Claudin-1 in the jejunum of the OE600 group was significantly lower than that of the other groups(P<0.05).(8)Intestinal transport carrier: At the 21 st day of age,the expression of PEPT1 in the jejunum of the OE200 group was significantly higher than that of the other groups(P<0.05),and the expression of PEPT1 in the OE400 group was significantly lower than that of the control(P<0.05);OE600 group The expression of CAT1 was significantly lower than the other groups(P<0.05);the expression of EAAT3 in the experimental group was linearly significantly increased(P<0.05);the expression of SGLT1 and GLUT2 in the OE200 group and the OE400 group was significantly higher than that of the control group and OE600Group(P<0.05);FATP4 expression in OE400 group and OE600 group was lower than that of control group and OE200 group(P<0.05).At the 48 th day of age,the expression levels of PEPT1,EAAT3,GLUT2,SGLT1 and FATP4 in the OE600 group were significantly higher than those in the other groups(P<0.05);the expression levels of PEPT1,EAAT3 and GLUT2 in the OE200 and OE400 groups were significantly lower than those in the control group(P<0.05);the expression of CAT1 in the experimental group was significantly reduced in linear and quadratic curves(P<0.05);the expression of SGLT1 in the OE200 group was significantly lower than that in the control group(P<0.05);the expression of FATP4 in the OE200 group was significantly lower In the control group(P<0.05).(9)The cecal microbial diversity: the Ace index and Chao1 index of the OE400 group were significantly higher than those of the other groups(P<0.05).According to Anosim analysis and PCoA,the structure of the cecal microbiota of the experimental group was different from that of the control group(P<0.05),and the structure of the cecal microbiota of the OE400 group was significantly different from that of the OE200 and OE600 groups(P<0.05).The OE200 and OE600 groups were The structure of the cecal microbial flora was not significantly different(P>0.05).LEfSe analysis found that oregano extract significantly increased the abundance of Lactobacillus and Faecalibacterium,and significantly reduced the abundance of Negativibacillus,Bacteroides,Eisenbergiella,Intestinimonas and Flavonifractor.There is a correlation between the caecal microflora and growth performance indicators of yellow feather broilers: Faecalibacterium has a significant negative correlation with F/G in the early and late stages.Lactobacillus is positively correlated with pre-ADFI,pre-and full-period ADG,and negatively correlated with pre-and full-period F/G.Negativibacillus is positively correlated with early,mid,full-period F/G and late ADFI,and negatively correlated with early and late ADG.Intestinimonas was positively correlated with mid-term ADG and negatively correlated with full-term ADG.Flavonifractor is negatively correlated with early ADFI and full-period ADG,and negatively correlated with mid-term F/G.The metabolic function of the cecal flora,the 21-day-old broilers of the OE400 group,the cecal flora chemoheterotrophy and fermentation metabolic pathways are enhanced.The above research shows that after treatment with thymol and carvacrol,the nucleic acid leakage of avian pathogenic Escherichia coli O78 and Salmonella pullorum increases,the cell migratory ability decreases,the biofilm formation ability decreases,and the growth rate decreases.Adding oregano extract to the diet of yellow feather broilers can improve the structure of intestinal microflora(such as increasing the proportion of beneficial bacteria and reducing the proportion of harmful bacteria),and enhance the digestion and absorption of nutrients(such as increasing the height of intestinal villi and the activity of digestive enzymes).And the expression of the transport vector),and then improve the growth performance of yellow feather broiler chicken(such as increasing the average daily gain and reducing the feed-to-meat ratio).From the perspective of growth performance indicators,adding 400 mg/kg oregano extract has the best effect. |
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