| Under the background of large-scale breeding,livestock and poultry diseases are becoming more and more complex.The use of antibiotics for the treatment of bacterial diseases will not only lead to imbalance of animal intestinal flora and drug resistance,but also food safety caused by drug residues is a serious threat to human health.As a rapidly developing alternative antibiotic product,plant essential oil has attracted much attention in livestock and poultry production.The most widely used plant essential oil monomers in animal husbandry mainly include thymol,carvacrol and cinnamaldehyde.However,the current research is mainly based on monomer essential oil,and there are few reports on compound essential oils.In order to explore the scientific and rational application of compound plant essential oils in pig industry,the compound plant essential oils prepared by mixing thymol,carvacrol and cinnamaldehyde in equal volume was used as the research object in this study.Based on the in vitro study,the antibacterial effect and minimum inhibitory concentration(MIC)of three plant essential oil monomers and compound plant essential oil on Escherichia coli,Salmonella and Staphylococcus aureus were detected by bacteriostatic test,electron microscopy and q RT-PCR.The effect of compound plant essential oil on the expression of inflammatory factors was investigated based on the inflammation model of porcine intestinal epithelial cells.Based on animal experiments,the compound plant essential oil was added to the basal diet of 22-day-old weaned piglets,and its effect on the growth performance of weaned piglets was detected after 60 days of feeding.Through HE staining and bacterial 16 S r DNA high-throughput sequencing,the changes of intestinal development,duodenal and rectal flora structure were detected and analyzed to clarify the effect of plant essential oil on intestinal digestion and absorption function of weaned piglets.The main results are as follows :(1)Study on antibacterial properties of plant essential oil in vitro.In order to explore the bacteriostatic effect of plant essential oil on pathogenic Escherichia coli,Salmonella and Staphylococcus aureus,the drug sensitivity test was carried out by filter paper diffusion method.The results showed that the three essential oil monomers and the prepared compound plant essential oils could inhibit the growth and reproduction of pathogenic bacteria,among which carvacrol had the strongest bacteriostatic effect,and the compound plant essential oils had the strongest bacteriostatic effect on Staphylococcus aureus.Further studies showed that the MIC of the compound plant essential oils against the three pathogenic bacteria was 0.42 μL/m L.By establishing a pathogen-induced inflammatory model of porcine small intestinal epithelial cells,it was found that the m RNA expression of inflammatory cytokines IL-1β,IL-6 and TNF-α was significantly inhibited after 6 hours of action of compound plant essential oils(P < 0.05).(2)Effects of compound plant essential oils on growth performance and intestinal development of weaned piglets.By analyzing and recording the growth and development data of experimental pigs,observing different intestinal lengths and different intestinal histopathology,it was found that compound plant essential oil could significantly increase the average daily feed intake and average daily gain of weaned piglets(P < 0.05),and reduce the incidence of diarrhea and diarrhea.At the same time,compound plant essential oils significantly promoted the intestinal development of weaned piglets.(3)Effects of compound plant essential oils on intestinal flora of duodenum and rectum in weaned piglets.The collected intestinal contents were processed and sequenced,and the sequencing results were interactively analyzed.The results showed that compound plant essential oils could optimize the composition of duodenal and rectal microflora in weaned piglets and increase the microbial richness in the intestine.Through species difference analysis,it was found that the compound plant essential oils could significantly increase the content of Subdoligranulum,unclassified Stenotrophobacteria,unclassified Peptostreptococcus in the duodenum of weaned piglets(P < 0.05),increase the content of Prevoella,Lachnospiraceae and Ucorymyceae UCG-005 in the intestine,which could degrade crude fiber,crude protein and utilize polysaccharide in the diet(P < 0.05),increase the content of Lactobacillus,Clostridium and Terrisporobacter in the rectum of weaned piglets,and significantly reduce the content of common intestinal pathogens such as Streptococcus(P < 0.05).In summary,the compound plant essential oils prepared by thymol,carvacrol and cinnamaldehyde has a significant bacteriostatic effect on common intestinal pathogens,which can improve the intestinal development level and flora structure of weaned piglets,significantly improve the growth and development level of weaned piglets,and reduce the diarrhea rate. |
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