Studies On The Characteristics And Derivation Of Precocious Strain Of E.acevulina In Chicken

To obtain high efficient and good immunogenicity coccidium vaccine and provide the theory of strains for producing chicken multivalent coccidiosis vaccine, the precocious strain of E.acervulina were gained by using single oocyst separating and precocious inducing technology. Subsequently, we determined the pathogenicity, productivity and immunogenicity of the precocious of E.acervulina. The results as follows:(1) Through single oocyst separating technology, purebred E.acervulina strain was acquired and its oocyst size was17.2μm～20.1μm×10.6μm～15.3μm and average:16.6μm×13.28μm, shape index:1.25. When chicken(21-day-old) were inoculated by E.acervulina with the dosage of10×104and20×104oocyst per chicken, the relative growth rate were91.87%and88.97%.(2) According purebred E.acervulina as parent strain, through precocious inducing technology, we achieved a77h latent period E.acervulina precocious strain, whose oocyst size was12.5μm～20.0μm×11.2μm～15.0μm and average:15.6μm×12.49μm, shape index:1.24.(3) Through studies on the Characteristics and Inducement of Precocious Strain of E.acevulina and Comparing with E.acervulina parent strain, the biological characterstics of E.acervulina precocious strain were conducted. The results suggested that:①The latent period of E.acervulina is77h, which is earlier19h than E.acervulina parent strain;②The pathologicity of E.acervulina precocious strain was significantly decreased. When chicken were inoculated by the precocious E.acervulina of with the dosage of0.5～20×104oocysts per chicken, there was no death, blood feces, but duodenum lesion of precocious strain was less than parent strain, relative weight growth rate was higher than parent strain. With the increase of the infection dosage, the adverse effects of the parent strain and precocious strains on chicken weight gain increased. When the dosages of E.acervulina precocious strains was1～10×104oocysts per chicken, the average weight of the difference was not significant (P>0.05); The dosages of E.acervulina precocious strains was over10×104oocysts per chicken, their average weight gain was significant lower than C group (P<0.05);③With the increased dosages, oocytes production of E.acervulina precocious strain and parent strain increase. When reach a invariably a dosages, oocytes production of E.acervulina precocious strain and parent strain decrease. However, the same dosages were inoculated, oocytes production of E.acervulina precocious strain was significant lower than parent strain. When breeding potential of oocytes is highest, the best dosages is1x104for E.acervulina parent strain, and0.5x104oocysts per chicken for E.acervulina precocious strain.(4) Terramycin, Oxytetracycline, Dinitolmide, Decouinate, Nicarbazin, Salinomycin and Sulfamonomethoxine group of POAA, RLS and ROP were negative;ACI was determined have part of the drug-resistant. Diclazuil and Madoumixing group of ROP were positive and ACI was determined have part of the drug-resistant. Drug sensitive test showed that:Seven kinds of anticoccidial drugs, including Terramycin, Oxytetracycline, Dinitolmide, Decouinate, Nicarbazin, Salinomycin and Sulfamonomethoxine were sensitivity for E.acervulina precocious strain. However, Diclazuril and Madoumixing was mild sensitive to E.acervulina precocious strain.(5) When the chicken were4days’old, once-immunization at different dosages were conducted and twice-immunization’s immunization were processed at4days’old and making the secondly14days’old. The results showed that:①Once-immunization have more seriously affect than twice-immunization for weight gain of chick. With the increased once-immunization and twice-immunization dosages, weight gain of chick decrease.②When dosages of once-immunization was1000per chicken, relative weight growth (82%) was80%or more, reduction of lesion scores (76.6%) was70%or more, oocytes inhibition rates(84.85%)was75%or more, ACI(174.2) was170or more and the highest lesion scores was1or more, which suggests protection effect of once-immunization was well. Its relative protect rate was92%. According twice-immunization, after200per chicken once-immunization and400per chicken twice-immunization’s immunization, have partial protective immunity; When once-immunization/twice-immunization was400/800per chicken, the highest lesion scores was1or more, RLS was70%or more, oocytes inhibition rates was75%or more, relative weight growth was90%or more which suggests protection effect of twice-immunization was well. The test showed that the minimum immune dosages of once-immunization was1000per chicken. the minimum immune dosages of twice-immunization was400/800per chicken. Twice-immunization’s immunization and weight gain influence were better than once-immunization in our study.