| Antibiotic abuse is affecting the development of the livestock industry,so the European Union and the Chinese Ministry of Agriculture have banned the addition of antibiotics to feed to reduce the harm of antibiotics to animals and humans,and to maintain public health and safety.The search for alternatives to antibiotics is imminent,and research on the use of essential oils from natural plants as alternative antibiotic substances has risen to the forefront,with unique physiological properties and functions that hold great promise for preventing bacterial infections and improving animal growth performance.Plant essential oils are secondary metabolites extracted from natural plants and have the ability to modulate immune function,anti-inflammatory,antibacterial,antioxidant,and protect the intestinal barrier.Most of the plant essential oils are made from safe natural materials,and their application as feed additives in animal husbandry can improve the appetite of animals and enhance the resistance of the organism to external pathogenic microorganisms.In this study,we firstly explored the inhibition effect of three plant essential oils on Salmonella in vitro and the mechanism of inhibition;then further applied the screened essential oils of cinnamaldehyde as feed additives to weaned piglets to observe their effects on growth performance and intestinal microorganisms of weaned piglets.1 Comparison of the antibacterial performance of three plant essential oils against SalmonellaIn order to investigate the inhibition performance of different plant essential oils on Salmonella and the effect on the bacterial cell wall and cell membrane,this experiment investigated the effect of plant essential oils on the cell wall and cell membrane morphology of Salmonella by determining the minimum inhibitory concentration of three plant essential oils,carvacrol,thymol and cinnamaldehyde essential oils,and then investigated the effect of plant essential oils on the cell wall and cell membrane morphology of Salmonella by mixing the fluorescent dye PI with DAPI after the action of plant essential oils The inhibition effect of plant essential oils on Salmonella was analyzed under flow cytometry and fluorescence microscope.The results showed that the MIC of carvacrol,thymol and cinnamaldehyde were 250μg/ml,the structure of Salmonella cell wall and cell membrane were damaged by plant essential oil,cell membrane permeability increased,the content of alkaline phosphatase in the medium increased significantly two-fold compared with the control group,and the content of lactate dehydrogenase generally increased three-fold significantly;it was observed by flow cytometry and fluorescence microscopy that plant essential oil changed It was observed by flow cytometry and fluorescence microscopy that plant essential oil changed the permeability of Salmonella cell wall and cell membrane,and promoted the penetration of fluorescent dyes PI and DAPI into the bacteria,among which the strongest fluorescence intensity of cinnamaldehyde essential oil group indicated that the inhibition effect of cinnamaldehyde essential oil on Salmonella was the most significant.2 The effect of three plant essential oils on the content of macromolecules,metabolism and infectivity of Salmonella in vivoIn this experiment,we firstly measured the levels of nucleic acid,ATP and protein in the medium of Salmonella after treatment with plant essential oil,and then examined the effect of plant essential oil on the cell membrane potential of Salmonella by labeling bacterial cell membrane with fluorescent probe Dibac4(3),and finally explored the effect of plant essential oil on the content of macromolecules,metabolism and infectivity of Salmonella in vivo by real-time fluorescence PCR to detect the expression level of virulence genes of Salmonella.The results showed that the nucleic acid,ATP and protein macromolecules in the bacteria were leaked to the bacteria by the treatment of three plant essential oils,and the levels of nucleic acid,ATP and protein in the culture medium were significantly increased;the fluorescence intensity of the cell membrane labeled by the fluorescent probe was reduced,indicating that the plant essential oils decreased the cell membrane potential of Salmonella,and the reduction of the cell membrane potential affected the energy metabolism level of Salmonella;the plant essential oils reduced the The expression levels of Salmonella transcriptional regulators HilA and HilC,invasion effector protein genes SipA,SipB and SipC were reduced,so that the functional proteins of Salmonella could not be synthesized normally thus affecting the ability of Salmonella to infect and invade the host cells.3 Effect of cinnamaldehyde essential oil on growth performance,serum biochemistry and intestinal microorganisms of weaned pigletsThis experiment investigates the effects of cinnamaldehyde,a plant essential oil,as a feed additive on growth performance,serum biochemistry and intestinal microorganisms of weaned piglets.The experiment was divided into two groups,the control group and the experimental group,with three replicates of 10 piglets in each group,and the experimental period was 21 days.The control group was fed the basal diet and the experimental group was fed the basal diet + 800mg/kg of cinnamaldehyde premix.The results showed that: the total protein content of serum was significantly higher in the cinnamaldehyde group,and the weaned piglets had good nutrient uptake;the cinnamaldehyde group was able to increase the ratio of the thick-walled phylum to the mimic phylum,enhance the body’s energy uptake and strengthen the fat deposition ability of the piglets;the essential oil of cinnamaldehyde increased the number of the beneficial intestinal flora Clostridiaceae-1,which can promote the repair of intestinal epithelial cells and maintain the structure and function of the intestinal mucosa It also reduced the number of harmful bacteria Prevotella and Trichoderma.and maintained the intestinal microbial barrier of the animal organism. |
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