Effect Of Essential Oils,Organic Acids And Coated Complex On The Performance And Intestinal Functions Of Laying Hens

As the laying period comes,the demand for nutrients increases markedly to satisfying the growth and production needs.Meanwhile,abundant using of limestone powder in feed meets the requirement of laying hens for production.But the pH value of gastrointestinal tract will be improved,which not only affects the intestinal digestion and absorption function but also increases the risk of intestinal diseases.The use of essential oil?EO?and organic acid?OA?in animal production will be beneficial to maintain good intestinal morphology,increase digestive enzymes activity,balance intestinal flora,and improve immune function of the body.In the present study,we investigate the effect of essential oils and organic acids and coated complex?EOA?on the performance,intestinal morphology,digestion and absorption function,and barrier function of 21-week-old to 35-week-old laying hens.It will provide the theoretical basis for the effective addition of organic acids and essential oils in layer hens production.Experiment 1 Effects of essential oils and organic acids and coated complex on the performance of laying hensA total of 756 21-week-old layers were allotted into six groups with 7 replicates and each replicate contained 18 birds.The experiment lasted 15 weeks.The birds in the control group were fed the basic diet whereas in other groups basic diet was supplemented with EOA at 150mg/kg,300 mg/kg and 450 mg/kg,OA at 300 mg/kg and EO at 300 mg/kg,respectively.The results showed that adding OA,EO or EOA to the diet had no significant influence?P>0.05?on the laying rate,AEW,ADFI and F/E compared to CON from 21 to 35 weeks.Adding EOA at 450 mg/kg or EO at 300mg/kg significantly increased yolk color at 30 weeks when compared with CON group?P<0.05?.Supplementation EO had the darker yolk color than feeding EOA at 300 mg/kg?P<0.05?.This study indicates that the addition of essential oils,organic acids and their coating complex to diets has no significantly influence on the performance of layer hens at 21 to 35 weeks.Adding EO to the diet contributes to the pigmentation and deepens the yolk color,finally.Experiment 2 Effects of essential oils and organic acids and coated complex on the intestinal digestion and absorption functions of laying hensIn the present study,we collected samples of small intestine of the laying hens at 25,30and 35 weeks.Paraffin sections were used to observe the changes of small intestinal morphology.RT-PCR was used to detect the mRNA abundance of mucosa enzymes and transporters in the process of digestion and absorption of nutrients.The results showed that dietary supplementation with 150 mg/kg EOA significantly increased the ratio of villus height to crypt depth in the duodenum when compared with adding EO and OA to the diet alone.And adding 450 mg/kg of EOA significantly reduced crypt depth in the jejunum of laying hens when compared to the addition of EO,at the age of 25 weeks?P<0.05?.Addition of 300mg/kg of essential oil to diet significantly reduced crypt depth of the duodenum of 35-week old hens when compared to the addition of 150 mg/kg EOA?P<0.05?.The hens that fed with essential oil-supplementation dietary had the higher mRNA abundance of maltase in the duodenum of laying hens at the age of 25 weeks?P<0.05?.The expression of aminopeptidase was significantly improved by adding 300 mg/kg EOA?P<0.05?.When treated with 300mg/kg EO,the expression of maltase in ileal mucosa of 30-week old laying hens was improved?P<0.05?.Relative expression of sucrase in duodenal mucosa of 35-week-old layer hens was improved by adding 300 mg/kg EOA?P<0.05?.Dietary supplementation with 300mg/kg EO significantly increased the relative expression of GLUT2 and FAPT1 in the duodenum of hens at 25 weeks of age?P<0.05?.The relative expression of ATB^0,+in the jejunum was improved by adding 150 mg/kg or 300mg/kg EOA to the diet?P<0.05?.And adding essential oils to diet significantly increased the expression level of b^0,+AT in the jejunum mucosa?P<0.05?.The results of this experiment indicate that high-dose supplementation of essential oils and organic acid coated complex is beneficial for working at distal intestinal tract.The addition of essential oil and 300 mg/kg coated complex to diet is more conducive to the expression of mucosal enzymes and transporters in the small intestine of laying hens at the age of 25 weeks and enhances the digestion and absorption of nutrients.Experiment 3 Effects of essential oils and organic acids and coated complex on the intestinal barrier functions of laying hensIn this study,mucosal samples of the small intestine and cecal chyme were used to measure the expression and content of relevant factors that play key roles in intestinal mucosal barrier function by RT-PCR and ELASA techniques.The number of microorganisms in the cecal chyme was determined by absolute quantification analysis.We observed that the addition of 300 mg/kg OA to the diet significantly increased the relative expression of Occludin-1 in ileum of 30-week-old laying hens?P<0.05?.The addition of essential oils increased the expression of ZO-1 in the duodenum of hens at 25 weeks of age and enhanced the expression level of ZO-1 in the ileum at 35 weeks of age,but there was no significant difference between the control group?P>0.05?.Compared with the control group,addition of450 mg/kg EOA or 300 mg/kg EO could significantly reduce the sIgA content in the ileum of laying hens at the age of 25 weeks?P<0.05?.At 30 weeks,supplementation with OA markedly reduced the number of lactobacilli in the caecum of laying hens?P<0.05?.So,the addition of essential oils and organic acids in diets contributes to the high expression level of ZO-1 and Occludin-1 in the intestinal mucosa,maintains good intestinal barrier function and cecal microbiota homeostasis.In summary,essential oil and 300 mg/kg coated complex supplementation also improves the digestion and absorption of nutrients in the intestine of laying hens at beginning of laying peak.However,each treatment has no remarkable effect on the performance and intestinal barrier functions of laying hens from 21to 35 weeks of age.