Study On Prevention And Treatment Of Avian Infectious Bronchitis By Baicalin

The wide spread of infectious bronchitis?IB?has caused great economic loss to poultry industry.In order to prevent and cure IB more effectively,radix scutellariae,as a medicine for expelling purging pathogenic heat,is selected among other herbal plants for its strong antiviral ability and the ability of immune adjustment.By using its effective component---baicalin,chickens are set as the target animals in the experiment of anti-IB to test the effect of baicalin on the chickens which were artificially infected with IBV.This study consists of three parts:1.The establishment of model of artificial infected chicken with IBV-M41.First of all,the chicken embryos was injected with the IBV-M41 which has been rejuvenated 3 times and the number of dead and survival chicken embryos were observed and recorded within 7 days.Then the EID₅₀ of IBV-M41 was calculated.According to the results of IBV-M41 virulence determination,the concentrations of IBV-M41 were set as100EID₅₀,101EID₅₀,102 EID₅₀ and 103EID₅₀.15 days old unimmunized chickens were intranasally infected with IBV-M41 at different concentrations and the best model infection dosage was decided by the morbidity and mortality of infected chickens.The results showed that the EID₅₀ of IBV-M41 was 10-4.32 /0.1m L,and the best model infection dosage was100EID₅₀.2.Screening of baicalin against IBV-M41 infection in chickens.One hundred and five 15 days old unimmunized white feather broilers were marked respectively before randomly divided into 7 groups of 15 chickens each.Group1 Group5 were treatment groups with baicalin at different doses.The dosages were 56,28,14,7 and3.5mg/kg/d.Group6 was the model control group and group7 was normal control group.Except the chickens of normal control group,all chickens were intranasally infected with IBV-M41?0.2m L?on 100EID₅₀/0.1m L.During the experiment,the feed intake,weight change,the number of diseased chickens and recovered chickens were recoded and the body weight gain,feed gain ratio,incidence and cure rate were calculated.In the end of the experiment,the immune organs index and phagocytosis of peritoneal macrophages of chickens were detected.The best dose of baicalin against IBV-M41 was determined through various indicators.The results showed that the body weight gain,feed gain ratio,incidence rate,cure rate,and the immune organs index with macrophage phagocytic ability of chickens in treatment groups with various doses of baicalin are better than the model group in different degrees.It showed that baicalin had an excellent effect against IBV-M41 and28mg/kg/d was the optimal concentration of baicalin against IBV-M41.3.The effect of baicalin against IBV-M41 in chickens.One hundred and fifty 12 days old white feather broilers were marked respectively and randomly divided into 10 groups of 15 chickens each.Group1 Group3 were prevention groups with various doses of baicalin?42,28,21mg/kg/d?and group4^group6 were treatment groups with various doses of baicalin?42,28,21mg/kg/d?.At 3 days before being experimentally infected with the virus,the chickens of prevention groups were given baicalin by oral gavage for 3 days.At 1 day past infection,treatment groups were given baicalin by oral gavage for 6 days.The group7 was Shuanghuanglian control group and group8 was Maxingshigan control group.The drug of group7 and group8 were dissolved in the potable water of chickens.The group9 was model control group and group10 was normal control group.Except the chickens of normal control group,all chickens were intranasally infected with IBV-M41?0.2m L?on 100EID₅₀/0.1m L.During the experiment,the feed intake,weight change,the number of diseased chickens and recovered chickens were recoded and the body weight gain,feed gain ratio,protection,incidence and cure rate were calculated.At the same time,the immune organs index,lymphocyte proliferation,lymphocyte subpopulation ratio and the cytokines level in serum were detected.The results showed that the protection rate of prevention group with baicalin was up to 46.67%,and the cure rate of the treatment group with baicalin was up to 80%.According to other indicators,baicalin could obviously improve the production performance,index of immune organs,lymphocyte proliferation and the rate of CD3+,CD4+and CD8+lymphocytes of chickens infected with IBV-M41.Meanwhile,baicalin could also maintain the ratio of CD4+/CD8+lymphocyte in a normal,constant range and regulate the level of IL-2,IL-4,TNF-?,IFN-?in serum to keep their dynamic balance.Through a comprehensive consideration of all the indicators,baicalin has better preventive and therapeutic effects on chickens infected with IBV-M41.Thereinto,the prevention group with high dose of baicalin?42mg/kg/d?and the treatment group with middle dose of baicalin?28mg/kg/d?had the most significant effect.