| In the context of the ban on antibiotics,the search for cost-effective alternatives to antibiotics has become a hot research topic in the feed industry.In this study,the effect of compound acidifier and essential oil on common pathogenic bacteria was initially investigated through in vitro antibacterial tests,and then the effect of compound acidifier and essential oil on growth performance,small intestine barrier function and meat quality of AA broilers was investigated through animal tests.The study was conducted to investigate the synergistic effect of the compound acidifier and essential oil to find the optimal amount of additive,thus providing an effective alternative to antibiotics,guiding the actual production and improving the economic efficiency of feed.Experiment 1 antibacterial effect of compound acidifier and plant essential oil on co mmon pathogenic bacteriaThe test adopted tube dilution method to determine the minimum inhibitory concentration（MIC）of compound acidifier and plant essential oil against Escherichia coli and Staphylococcus aureus,and then the fractional inhibitory concentration index（FICI）of compound acidifier and plant essential oil was determined by checkerboard method.The results showed that: 1)The MIC of compound acidifier alone was 2mg/m L for Staphylococcus aureus and 0.5mg/m L used in combination;The MIC of plant essential oil alone was 2mg/m L and 1mg/m L used in combination;The FICI was 0.75 and the effect was additive.2)The MIC of compound acidifier alone for Escherichia coli was 2mg/m L and0.5mg/m L used in combination;The MIC of plant essential oil alone was 2mg/m L and0.25mg/m L used in combination;The FICI was 0.375 and the effect was synergistic.In conclusion,chompound acidifier and plant essential oil have good bacteriostatic effects on Escherichia coli and Staphylococcus aureus.When used alone,the MIC were both 2mg/m L,and the bacteriostatic effect was enhanced used in combination.The bacteriostatic effect of combined use on Escherichia coli was synergistic,and the bacteriostatic effect of combined use on Staphylococcus aureus was additive.Experiment 2 Effects of compound acidifier and plant essential oil on growth performance,slaughter performance,meat quality and nutrient utilization of AA broilers360 1-day-old AA broilers were randomly divided into 6 groups,with 5 replicates in each group,12 feathers in each replicate,half male and half female.The negative control group（NC）was fed an antibiotic-free basal diet;The positive control group（antibiotic group,PC）was fed a basal diet supplemented with 250 mg/kg of aureomycin and 60 mg/kg of enramycin;Group I（T1）was fed a basal diet+2 g/kg of compound acidifier;Group II（T2）was fed a basal diet+200 mg/kg of essential oil;Group III（T3）was fed basal diet+2 g/kg compound acidifier+200 mg/kg essential oil;Group IV（T4）was fed the basal diet+1 g/kg compound acidifier+100 mg/kg essential oil.The experimental period was 42 d.The results showed that: 1)Compared with the NC group,the average daily feed intake（ADFI）and average daily weight gain（ADG）for the whole period from 22 to 42 d in T3 and T4 were significantly increased（P<0.05）and as well as the ADG for the whole period in T1 and T2groups（P<0.05）.Compared with the PC group,ADFI and whole period ADG from 22-42 d in T4 were significantly increased（P<0.05）.2)Slaughter rate was significantly higher in each treatment compared to the NC group（P<0.05）,and T4 in turn had a significantly higher slaughter rate compared to all other groups（P<0.05）.3)There were no significant differences in drip loss,cooking loss and meat colour in each group（P>0.05）.4)Compared with the NC group,the nutrient utilization of calcium was significantly higher in each group（P<0.05）;The nutrient utilization of phosphorus was significantly higher in the PC group,T1,T3 and T4（P<0.05）,and T4 in turn had a significantly higher nutrient utilization of phosphorus compared to other three groups（P<0.05）,as also T3 was significantly increased compared with T2;The nutrient utilization of organic matter and dry matter were significantly increased in the test groups（P<0.05）and higher than the PC group（P<0.05）.Conclusion: The combination of acidifier and essential oil promoted the growth performance,slaughter performance,meat quality and nutrient utilization of AA broilers,and the combination of the two was more effective than using them alone,and the combination of acidifier 1 g/kg + essential oil 100 mg/kg had the best effect.Experiment 3 Effects of compound acidifier and plant essential oil on intestinal barrier function in AA BroilersThe experiment materials and methods were the same as experiment 2.The results showed that: 1)Compared with the NC group and PC group,the duodenal villi height/crypt depth（V/C）was significantly increased in T1（P<0.05）,the V/C of duodenum and jejunum were significantly increased in T4（P<0.05）,and the duodenal V/C was significantly increased in T4 compared to T2 and T3（P<0.05）.The ileal V/C values were significantly increased in the T1,T2 and T3（P<0.05）.There were no significant differences in the villi height（VH）,crypt depth（CD）and intestinal wall thickness in the duodenum,jejunum and ileum of each group（P>0.05）.2)Compared with the NC group and PC group,there were no significant differences in the gene expression levels of ZO-1,occludin,MUC1 and MUC2 in each group（P>0.05）.3)Cecum diversity: Compared with the NC group and PC group,the OTUs,Chao1 and PD indices of T1 were significantly increased;The ACE index was significantly higher than that of the NC group（P<0.05）;The ACE,OTUs,Chao1 and PD indices of T3 and T4 were significantly increased（P<0.05）,and the Shannon index was significantly higher than that of the NC group（P<0.05）.Between the experiment groups,the OTUs index of T2 was significantly lower than that of T4（P<0.05）and the PD index was significantly lower than T3 and T4（P<0.05）.The microbial composition of the cecum: at the phylum level,the abundance of the soft-walled phylum was significantly higher in the T4 group than in all other groups（P<0.05）,while there were no significantly differences in the abundance of the thick-walled phylum,the phylum Bacteroides,and the phylum Aspergillus（P>0.05）.At the genus level,the abundance of the genus UCG-014 in the T4 group was significantly higher than all other groups（P<0.05）,while there were no significantly differences in the abundance of other dominant genera（P>0.05）.Conclusion: The compound acidifier and plant essential oil significantly increased the ratio of VH/CD in duodenum,ileum and jejunum,improved the intestinal morphology of white feather broiler chickens,increased the expression level of jejunal barrier genes to a certain extent,significantly increased the diversity and abundance of cecum microorganisms and the abundance of beneficial bacteria,improved the structure of bacterial flora and enhanced the barrier function of the small intestine of AA broilersIn summary,the addition of acidifier and essential oil to the diet of AA broilers significantly improved the growth performance,small intestinal barrier function and meat quality to a certain extent,and was an effective alternative to antibiotics.The combination of the two was more effective than using them alone,and the combination of acidifier 1 g/kg + essential oil 100 mg/kg had the best effect. |
