| Coccidiosis is caused by coccidiosis of the genus Eimeria in the intestinal epithelial cells of chickens,which severely endangers the poultry industry.Among them,Eimeria tenella(E.tenella)parasiticis to the cecum of chickens is most harmful.In the context of restricting the use of antibiotic feed additives,there has not been reported whether acidifiers which commonly used in livestock and poultry production have a prevention and control effect on chicken coccidiosis.The purpose of this study was to explore the effects of coated acidifiers on the growth performance and intestinal barrier of E.tenella-infected broilers,providing novel ideas for the prevention and control of chicken coccidiosis.A total of 180 1-day-old Lingnan yellow broiler chickens were divided into 6 treatment groups,GroupⅠ was set as control group and fed the basic diet;Group Ⅱ was the low-dose infection group(1.5×104 oocysts/head);Group Ⅲ was the high-dose infection group(3×104 oocysts/head);Group Ⅳ was the acidifier treatment group(0.06%);Group Ⅴ was the acidifier treatment+low-dose infection group(0.06%+1.5×104 oocysts/head);Group Ⅵ was the acidifier treatment+high-dose infection Group(0.06%+3×104 oocysts/head),groups Ⅳ,Ⅴ and Ⅵ were added with 0.06%coated acidifiers to the basic diet from 1 day of age,sporulated E.tenella oocysts were inoculated through craw at the age of 14 days.After 0 d(14 days of age),4 d(18 days of age),7 d(21 days of age),10 d(24 days of age),and 15 d(29 days of age),samples were collected for index determination,and the body weight gain,weight/gaint ratio,pH of the intestinal contents and serum endotoxin were measured.Pathological sections were made to observe the cecum mucosa epithelial morphology.Real-time quantitative PCR and Western blotting were used to analyze the expression of intestinal tight junction protein,and 16S rRNA gene sequencing was used to determine the intestinal flora.The results were shown as following:(1)At the age of 1 to 14 days,the weight gain of broiler chickens in the acidifier treatment group was significantly higher than that of the control group(P<0.05);at the age of 14 to 24 days,the weight gain of broiler chickens in the E.tenella infection group was significantly lower than that of the control group(P<0.05);the weight gain of group Ⅳ at 24-29 days was dramatically higher than that of group Ⅰ(P<0.01).At the age of 1-14 days,the feed/gain ratio of the acidifier treatment group decreased significantly compared with the control group(P<0.01);at the age of 14-18 and 18-21 days,the feed/gain ratio of the group Ⅱ and Ⅲ were significantly higher than that of the group Ⅰ(P<0.05),the feed/weight ratio of groupⅣ was significantly lower than that of group Ⅰ(P<0.05),and the feed/weight ratio of group Ⅴ and Ⅵwas dramatically lower than that of group Ⅱ and Ⅲ(P<0.05);during 21-24 days and 24-29 days,the feed/weight ratio of group Ⅲ was significantly higher than that of other groups(P<0.01).At 14 days,the pH of the small intestine and cecum contents in group Ⅳ were significantly lower than control group(P<0.05);at 18 and 21 days of age,the pH of the small intestine contents of the Ⅳgroup were notably lower than those of other groups(P<0.01).The pH of the small intestine contents in group Ⅲ was significantly higher than that in group Ⅰ(P<0.05);there was no significant difference in small intestinal pH between groups at 24 and 29 days of age(P>0.05).At 21,24 and 29 days of age,the pH of the cecum contents of group Ⅲ was significantly higher than the other groups(P<0.05);at 21 and 24 days of age,the pH of the cecum contents of group Ⅳ was notably lower than the other groups(P<0.01).(2)At 14 days of age,the serum endotoxin of the acidifier treatment group was significantly lower than the control group(P<0.05);at 18 and 21 days of age,the serum endotoxin of groups Ⅱ and Ⅲ was significantly higher than that in the group Ⅰ(P<0.05);the serum endotoxin content in group Ⅳ decreased significantly(P<0.05),and the serum endotoxin of groups Ⅴ and Ⅵ was significantly lower than those in groups Ⅱ and Ⅲ(P<0.05);at 24 days of age,the serum endotoxin of group Ⅱlwas significantly higher than group Ⅰ(P<0.05),and the serum endotoxin of group V was significantly lower than that in group Ⅱ(P<0.05).(3)Pathological tissue section showed that there were some typical pathological features in E.tenella-infected broilers,such as the damaged cecum mucosa,the shed epithelial cell,the reduced number of intestinal glands,and a large number of schizonts in the interstitial.At the later stage,a large number of round cystic wrom eggs can be seen,the intestine gland expanded and a small amount of necrotic cell fragments were seen in the intestinal lumen;acidifiers caused a large number of heteroeoblast infiltration in the cecum epithelium during the recovery phase of coccidiosis infection,but acidifiers had no significant effect on the recovery of intestinal mucosa of E.tenella infected broilers.(4)Real-time quantitatⅣe PCR and Western blotting analysis revealed that the expression of Occludin in the intestine 4 d after E.tenella infection was increased,which may be a manifestation of the body anti-damage response;7 d after infection,the expression of tight junction protein in the small intestine and cecum decreased,it gradually rises to normal.Acidifier can promote the expression of intestinal tight junction protein in broiler chickens,but use acidifiers during E.tenella infection will exacerbate the downward trend of expression of tight junction proteins caused by infection.(5)E.tenella infection will lead to a decrease in the cecum Firmicutes,an increase in the cecum Proteobacteria and the unidentified-Enterobacteriaceae,while the addition of acidifiers in feed can increase Bacteroidetes of cecum,Lactobacillus of the small intestine and the microbial diversity of cecum.The results of this study suggest that addition of acidifiers in the diet can improve the growth performance of E.tenella infected yellow broilers,improve intestinal health,and have partly positive significance for the prevention and control of chicken coccidiosis. |
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