| With the emergence of antibiotic prohibition policy and the prominent problems of intestinal health of poultry,green antibiotic-free feeding has become the most urgent problem to be solved.Chlorogenic acid has strong biological functions in anti-inflammatory,antibacterial,antiviral,antioxidant and other aspects,but its application and dosage in chickens diets are still not clear.In this study,the optimal supplemental level and antioxidant capacity of chlorogenic acid on broilers were evaluated by measuring performance,organ development,blood biochemical indexes,intestinal antioxidant activity and related gene expression and cecal microbial sequencing.A total of 384 one-day-old Arbor Acres broilers with similar body weight were randomly assigned to 4 groups with 12 replicates per group and 8 broilers per replicate.One group was fed a basal diet,while the other three groups were fed the basal diet supplemented with 250 mg/kg,500mg/kg and 1,000 mg/kg chlorogenic acid,respectively.Production performance was recorded weekly.At 21 and 42 days of age,8 chickens were randomly selected from each treatment for blood sampling and slaughter.Blood was collected to separate the serum.Organs such as breast muscle,thigh muscle,duodenum,jejunum,ileum,cecum,liver,thymus,spleen and bursa of Fabricius were taken to weigh.Meanwhile,the length of duodenum,jejunum,ileum and cecum was measured.Duodenum,jejunum and ileum samples were taken to extract RNA.Cecal chyme was taken at 42 days of age to microbiome sequencing.The results showed that 250 mg/kg and 500 mg/kg chlorogenic acid could decrease the feed/gain ratio of broilers（P < 0.05）.1,000 mg/kg chlorogenic acid reduced the daily gain of broilers 1-3 weeks（P < 0.05）,but did not affect the performance of broilers during 4-6 weeks（P > 0.05）.Chlorogenic acid supplementation had no significant effect on organ index（P > 0.05）and muscle percentage（P > 0.05）of broilers.Chlorogenic acid can increase serum albumin and triglyceride content（P < 0.05）and decrease serum uric acid content（P < 0.05）,but had no significant effect on other biochemical indices（P > 0.05）.Chlorogenic acid can increase the total antioxidant capacity of blood（P < 0.05）.At 21 days of age,the m RNAexpressions of SOD2,CAT,GSS and GSR in duodenum and jejunum of chlorogenic acid group were significantly decreased（P < 0.05）,but the expression of GPx7 gene in 1,000 mg/kg chlorogenic acid group was significantly increased（P <0.05）and there were no significant changes in MDAand GSH contents（P > 0.05）,indicating that no peroxidation occurred in the intestinal tract.At 42 days of age,Nrf2,SOD1,SOD2 and CAT gene expressions in ileum of 1,000 mg/kg chlorogenic acid group were significantly up-regulated（P <0.05）,indicating the antioxidant capacity of chlorogenic acid.Chlorogenic acid may regulate intestinal flora by increasing the abundance of Firmicutes and Alistipes and decreasing the abundance of Proteobacteria and other harmful bacteria,but it does not improve the Alpha and Beta diversity of intestinal flora.In conclusion,the recommended supplemental dose of chlorogenic acid is 250 mg/kg（chlorogenic acid is an extract of eucommia ulmoides with a total acid content of 50%）,which can reduce feed/gain ratio and improve performance of broilers.Compared with the early growth stage,the effect of chlorogenic acid on the antioxidant capacity of intestinal tract（especially ileum）was more obvious in the late growth stage,which might be one of the reasons for improving the production performance.Feeding chlorogenic acid did not significantly affect the Alpha and Beta diversity of cecal microflora of broilers,but could regulate the abundance of dominant microflora. |
