Immunoprotection Against Avian Coccidiosis By In Ovo Vaccination With Eimeria Tenella, E.acervulina AND/OR E.maxima OOCYSTS

Oocysts were detected on d 19, 20 of incubation after in ovo injection of certain doses of E.tenella sporolated oocysts on d 18 of incubation through amniotic sac. Oocysts detecting of gizzard, intestine was also done during 1~4 d post-hatch. Schizonts were detected in mucosa of ceca. The results show that oocysts can be detected in feather, gizzard and intestine of embryo on d 20 incubation, 2 d post injection, meanwhile, the second generation schizonts can be detected in ceca of chickens on d 4.5 post-hatch. All of those indicated that although oocysts injected on d 18 of incubation through amniotic sac can flow in intestine of embryo, infection by E.tenella was established post-hatch.The efficacy of immunoprotection against avian coccidiosis by delivery in ovo oocysts of E.tenella and/or E.acervulina and/or E.maxima was investigated. The fertile Lingnanhuang broiler eggs were injected through amniotic sac on d 18 of incubation with oocysts of E.tenella and/or E.acervulina and/or E.maxima. The dose were in the range of 1×103~1×105 oocysts/egg. No significant effect on hatch rate was observed. Hatched chicks were reared in wire-cages and oocyst outputs of each high dose group were detected using OPG (oocysts per gram feces) during 1～11 d post-hatch. The vaccinated chicks were challenged with high dose homologous Eimeria oocysts at 14 d post-hatch, and the immunity against homologous Eimeria oocyst challenge were evaluated by relative weight gain (RWG), feed conversion rate (RCR) and relative oocyst production (ROP). The results showed that the prelatent period and the output peak of oocyst that injected in ovo were similar to that of chicks vaccinated per os at one-day-old. The initial oocyst production occurred on 4 d (E.acervulina) or 5 d (E.tenella, E.maxima) post-hatch. Both of the peak times were at 6 d (E.acervulina) or 7 d (E.tenella, E.maxima) post-hatch. The similar dynamics of oocyst outputs suggested that the parasite life cycle was initiated around the time of hatching.Chicks vaccinated by in ovo injection with Eimeria oocysts on 18 d of incubation improved RWG from 21.1%～54.7%(nonimmunized challenged control) to 56.0 %～86.4%...