Effects Of Tea Tree Oil On Growth Performance And Intestinal Barrier Function Of Weaned Piglets

In the pig production,how to improve the pig's growth performance and feed utilization,improve immunity,reduce the rate of diarrhea,has been a hot spot in the pig industry.Seeking ecological and green growth-promoting feed additive to replace antibiotics is one of the research hotspots in animal nutrition field.The aim of this study was to explore the effects of tea tree oil on growth performance,diarrhea,intestinal structure,intestinal mucosal antioxidant activity and immune function of weaned piglets,and explore the feasibility of substituting antibiotics.One hundred and twenty Duro x Landrace x Yorkshire crossbreed weaned piglets?21-day-old,6.73±0.12kg?were randomly divided by weight into five groups:CON group?basal diet?,ANT group?basal diet+200 mg/kgcolistin?10%?+75 mg/kg chlortetracycline?15%??,LTO group?basal diet+50mg/kg tea tree oil?,MTO group?basal diet+l00mg/kg tea tree oil?and HTO group?basal diet+150mg/kg tea tree oil?,with six replicates per group,male and female in half,and four pigs per replicate.The experiment lasted for 21 d.The whole research consisted to the following three parts.Experiment 1:Effects of tea tree oil supplementation on the growth performance,serum biochemical and organ indexes of weaned pigletsThe experiment was carried out to investigate the effects of tea tree oil on growth performance,diarrhea,serum biochemical and organ indexes of weaned piglets.Average daily gain?ADG?,average daily feed intake?ADFI?,the ratio of feed to gain?F/G?,diarrhea rate and diarrhea score were recorded and calculated during the experiment.At the end,weight,blood and slaughter,the serum biochemical and organ indexes were test.The results showed as follows:1)Compared with CON group,ADG of MTO group and HTO group increased by 8.33%and 14.84%?P<0.1?respectively,and F/G of MTO group and HTO group were 9.58%and 7.78%lower than CON?P>0.05?.2)Diarrhea rate and diarrhea score of ANT,MTO,HTO were significantly lower than that of CON?P<0.05?,of which MTO was the lowest.3)Compared with ANT group,MTO and HTO groups' AST and GGT were significantly reduced?P<0-05?,LTO and HTO groups' GLU significantly decreased?P<0.05?,there were no significant difference in ALT,TP,ALB,GLO and A/G among groups?P>0.05?.4)MTO and HTO groups' liver index and LTO group's thymus index were significantly higher than ANT group?P<0.05?.In summary,adding a certain percentage of tea tree oil to diet of weaned piglets could promote the growth while reduce diarrhea.Tea tree oil could promote the development of liver and thymus and with a certain degree of regulate metabolism.To a certain extent,tea tree oil can replace the use of antibiotics.Experiment 2:Effects of tea tree oil supplementation on the intestinal physical barrier and chemical barriers of weaned pigletsThis experiment was to to investigate the effects of tea tree oil on intestinal physical barrier and chemical barrier in weaned piglets.The duodenum,jejunum and ileum were isolated from the slaughtering piglets,weighing and measuring length to analysis the intestinal development condition.The intestinal villus height and crypt depth were measured by making paraffin sections,hematoxylin-eosin staining and optical microscopy observation.Intestine middle organization samples were made into ultra-thin slicing,the effects of different treatments on the ultrastructure of small intestinal epithelium were observed by transmission electron microscopy.Detected the antioxidant enzymes activities of jejunum and ileal mucosa to analysis the changes of anti-oxygen function.The results indicate:1)Compared with the control group,the duodenal length and duodenum relative weight of MTO group were significantly increased?P<0.01?,jejunum/ileum length of MTO group was significantly higher than that of CON group?P<0.05?,and jejunum weight tends to increase?P<0.1?.2)Tea tree oil added in weaned piglets' diets significantly increased duodenum,jejunum and ileum villus height?P<O.01?.The ratio of villus height to crypt depths of duodenum,jejunum and ileal of piglets in tea tree oil treatment groups were significantly increased compared with the CON and ANT groups?P<0.01?.3)Intestinal villuses of piglets in tea tree oil treatment groups were more inerratic and tidier than those in CON and ANT groups,the development is relatively good.Besides,the microvilli of the intestinal epithelium in tea tree oil treatment groups were more slender,neat and dense than the CON group and the ANT group.4)The activity of GSH-PX and SOD in jejunum mucosa of HTO group was significantly higher than that of ANT group?P<0.05?.The content of H2O2 in the jejunum mucosa was significantly higher than that in ANT group and tea tree oil treatment groups?P<0.01?.The activity of SOD and GSH in ileum mucosa of HTO group was significantly higher than that of CON group?P<0.05?,while the content of MDA in ileum mucosa of CON group was significantly higher than that of other groups?P<0.01?.These proved that tea tree oil added in weaned piglets' diets can promote intestinal development,the intestinal tissue structure is more perfect,and to a certain extent improve the intestinal mucosal antioxidant function,which has a certain enhancement of intestinal physical barrier and chemical barrier function.Experiment 3:Effects of tea tree oil supplementation on the intestinal mucosal immune barrier of weaned pigletsThe aim of this test was to investigate the effects of tea tree oil on intestinal mucosal immune barrier function of weaned piglets.The levels of immunoglobulin and cytokines in serum and intestinal mucosa were detected by enzyme-linked immunosorbent assay?ELISA?.Real-time PCR was applied to evaluate the gene expression associated with intestinal barrier.The results manifested:1)The levels of IgA and IgG in serum of MTO group were significantly increased?P<0.05?.The levels of IL2,TNF-? and IFN-y in serum of MTO group and HTO group were significantly increased?P<0.05?.There was no significant difference in serum IL1?,IL10 and IL12 levels?P>0.05?.2)Compared with CON group,the content of sIgA in jejunum and ileum mucosa has a tendency to increase?P<0.1?,the levels of IL2 and IL10 in jejunum mucosa of HTO group were significantly increased?P<0.05?,the levels of IL2,IL10,IL12,IFN-y and TNF-a in ileum mucosa of HTO group were significantly increased?P<0.05?.3)Compared with CON group and ANT group,the expression of IL1? gene in the jejunum of MTO group was significantly increased?P<0.01?,and the expression of IL2 gene was significantly increased in MTO group and HTO group?P<0.05?.The expression of TNF-a gene in the ileum of ANT group and the MTO group was significantly higher than that in the other groups?P<0.01?.4)Compared with CON group,the occludin gene expression of jejunum was significantly increased in MTO group,HTO group and ANT group?P<0.01?,and the occludin gene expression of ileum in LTO group was significantly increased?P<0.01?.The expression of MUC2 gene in the jejunum of MTO group was significantly higher than other groups?P<0.0 1?.It can be seen that adding proper amount of tea tree oil to the piglets' diet could increase the secretion of serum immunoglobulin and cytokines to a certain extent,increase the secretion of cytokines in intestinal mucosa,regulate the expression of immune barrier-related genes in intestinal mucosa,and enhance the immunity,which can improve the intestinal mucosal immune barrier function of weaned piglets.Experiment 4:Effects of tea tree oil supplementation on the intestinal microbial barrier of weaned pigletsIn this study,the 16S rDNA high-throughput sequencing technique was used to reflect the effect of tea tree oil on gut microflora in weaned pigs.The purpose was to explore the effect of tea tree oil from the perspective of intestinal biological barrier.The results showed as follows:1)OTUs in tea tree oil treatment group were higher than those in CON group and ANT group.2)Analysis of the a-diversity in the microflora showed that the ACE index was significantly up-regulated in the LTO and HTO groups?P<0.01?,shannon index of tea tree oil treatment group tend to increase compared with CON?P<0.1?.3)?-diversity analysis showed that microbial flora in CON and ANT groups were similar.The flora structure of tea tree oil treatment groups were similar,while the flora structure of tea tree oil treatment groups were different from CON group and ANT group.4)The abundance of firmicutes in MTO group and HTO group were significantly higher than that in CON group and ANT group?P<0.O1?,and the abundance of bacteroidetes in MTO group and HTO group were significantly lower than that in CON group and ANT group?P<0₀1?.5)Compared with the ANT group,the abundance of Clostridium_sensu_stricto₁ in MTO group and HTO group was significantly increased?P<0.05?,the abundance of Prevotellaceae_NK3B31_group in the LTO group and HTO group were significantly decreased?P<0.05?,Prevotella₂ of MTO group and HTO group were significantly lower than those in CON group and ANT group?P<0.05?.Thus,tea tree oil may beappropriate to increase the abundance and diversity of intestinal microflora,improve the structure of microbial flora in intestinal.Based on the test results above,the appropriate dosage of tea tree oil could promote growth while reduce diarrhea of weaned piglets,motivate the development of liver and thymus,and regulation of metabolism to a certain extent.It also can accelerate intestinal development,the intestinal tissue structure is more perfect,and the antioxidant injury function of intestinal mucosal improved.The secretion of immunoglobulin and cytokine were increased,and the expression of immune barrier-related genes were regulated.In addition,tea tree oil could increase the abundance and diversity,improve the structure of intestinal microflora.Tea tree oil has a certain role in enhancing the intestinal physical barrier,chemical barrier,immune barrier and biological barrier function,could replace the use of antibiotics to a certain extent.