protection efficacy of multivalent egg yolk immunoglobulin against eimeria tenella infection in chickens.

background: to control avian coccidiosis with drug-independent strategy effec-tively and safely, multivalent hyperimmune egg yolk immunoglobulin (igy) was prepared and its ability to protect against eimeria tenella infection was evaluated. methods: hens were orally immunized with live oocysts of 5 species of eimeria for six times, antibody titers in serum and yolk were monitored by indirect enzyme-linked immunosorbent assay. the specific igy was isolated, purified and lyophi-lized. igy powder was orally administrated as dietary supplement in newly hatched chicks at various dosages. birds were orally challenged with 10000 sporulated oo-cysts of e. tenella at 10 days of age, weighed and killed at 8 days post challenge, and the protective effect was assessed. results : the averge yeid of igy was 9.2 mg/ml yolk, the antibody titer of igy reached to 1:163840 per mg with the purity up to 98%. chickens fed igy resulted in reduced mortality, increased body weight gain (bwg), reduced oocyst shedding, reduced caecal lesion score and increased anti-coccidial index. in terms of bwg and caecal lesion, igy significantly enhanced the resistance of bird at ≥ 0.05% of igy in the diet when compared with the challenged control group ( p <0.05). no significant difference was observed at dosage ≥ 0.5% and 1.0% when bwg and caecal lesion were compared with the sodium salinomycin control group, respec-tively ( p >0.05). conclusion : supplementing newly hatched chicks with eimeria -specific igy repre-sents a promising strategy to prevent avian coccidiosis.