Effects Of Rosemary Extract On Performance,Antioxidant Capacity And Intestinal Health Of Yellow-feathered Broilers Challenged With Escherichia Coli.

Rosemary(Rosmarinus of ficinalis L.)belongs to the labiatae and its main active compounds are:rosemary acid,ursolic acid,hesperidin and quercetin and other flavonoids,with antioxidant,antibacterial,antiviral,anti-diabetic,anti-inflammatory,antidepressant and other biological effects.This experiment aimed to explore the effects of rosemary extract on the growth performance,organ index,serum biochemical and antioxidant properties and intestinal health of E.coli(Escherichia coli)challenged broilers.The experiment adopted a single factor completely random design.A total of 144yellow-feathered female broilers of 1d old were randomly divided into 3 groups,6replicates in each group,and 8 broilers per replicate.The preliminary feeding period lasted for 7 days,and the experiment period lasted for 28 days(8 days old to 35 days old).Experimental design:Control group(CON)chickens were fed a basal diet,starting from the 29th day of age,each chicken was fed 2 ml sterile normal saline.Chickens in E.coli challenge group(EC)were fed a basal diet,and each chicken was fed 2 ml of E.coli K88solution with a concentration of 1.0×10~9 CFU/m L at the 29th day of age for 7 consecutive days.Rosemary extract+E.coli challenged group(ECRE):the basal diet was supplemented with 400 mg/kg rosemary extract,and they were challenged with E.coli solution as in EC group at 29 days of age.At the end of the experiment,one chicken was randomly selected from each replicate of each group for slaughter and relevant samples which collected for determination.Statistical analysis results show that:The dietary addition of rosemary extract had no significant effect on the average daily feed intake,average daily gain and feed conversion ratio of 8～28-day-old yellow-feather broilers(P>0.05).At 29 to 35 days of age,adding rosemary extract in the diet could increase the daily gain of broilers challenged with E.coli(P<0.05),and reduce the feed conversion ratio and diarrhea rate(P<0.05);The addition of rosemary extract in diet could improve the organ index of E.coli challenged broilers by increasing the spleen index(P<0.05)and reducing the liver index(P<0.05);The addition of rosemary extract in diet could reduce the increase of urea content(P<0.05),increase the glucose content(P<0.05),and reduce the lactate dehydrogenase activity(P<0.05)in serum of broilers challenged with E.coli to improve the metabolic function.However,rosemary extract also increased the serum aspartate aminotransferase content of E.coli challenged broilers to a certain extent(P<0.05);The addition of rosemary extract in diet could improve the activities of serum T-AOC,GSH-Px and CAT in E.coli-infected broilers(P<0.05),thereby slowing down the oxidative stress injury of E.coli-infected broilers.The activity of T-AOC in serum was significantly higher than that in the control group(P<0.05).The addition of rosemary extract in diets reduced the ileal crypt depth(P<0.05)and increased the ratio of ileal villus height to crypt depth(P<0.05).For cecum content microorganisms,at the phylum level,the addition of rosemary extract in diets increased the relative abundance of Firmicutes(P=0.075)and decreased the relative abundance of Proteobacteria(P<0.05).At the genus level,the addition of rosemary extract in the diet could reduce the richness of Bacteroides(P<0.05),and increase the richness of Ruminococcus torques and Dorea(P<0.05),so as to improve the microbial community structure in cecum.In conclusion,the addition of 400 mg/kg rosemary extract in diets could alleviate the adverse effects of E.coli challenge on yellow-feathered broilers by improving organ index,regulating serum biochemistry,improving antioxidant capacity,improving intestinal morphology and cecal microbial community structure,thereby improving their growth performance.