Résumé
To control avian coccidiosis with drug-independent strategy effectively and safely, multivalent hyperimmune egg yolk immunoglobulin [IgY] was prepared and its ability to protect against Eimeria tenella infection was evaluated. 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 lyophilized. 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. The average yield 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, respectively [P>0.05]. Supplementing newly hatched chicks with Eimeria-specific IgY represents a promising strategy to prevent avian coccidiosis