Doença de Gumboro : influência dos anticorpos maternos sobre as vacinações "in ovo", injetável e na água de bebida e desempenho de frangos de corte.

Abstract

A comparison of vaccinating 18-day embryos (in ovo) or chicks at the 1st day or 15th day post hatch against infectious bursal disease (IBD) was performed. The experimental embryos and chicks were progeny of industrial broiler breeders with high (given IBD oil-emulsion vaccine) or low (not given IBD oil-emulsion vaccine) serum antibody titers against IBD virus (IBDV). Hatched progenies were female broilers derived of the same breeders generating the embryos. Chickens were evaluated for IBDV serum antibody assay (serum neutralization), vaccinal IBDV (RT/PCR) infection in the bursa of Fabricius (BF) and for the evaluation of performance at the 40th day of age. The experimental design constituted of a 2 x 3 factorial (two breeder groups: given or not inactivated oil-emulsion vaccine at the 18th week of age; three progeny broiler groups according to the date of given IBDV intermediate strain vaccine: at the 18th day of embryonic development, 1st or 15th day post hatch). The performance of chicks at the 40th day of age was not affected by in ovo or day-old vaccinations for any level (low or high) of passive antibodies. Broilers of low passive antibody titers, vaccinated in ovo, on the 1st or 15th day post hatch seroconverted to higher titers (p<0,05). Unvaccinated breeder progenies developed a higher circulating antibody response (serum neutralization) possibly due to a higher rate of vaccinal IBDV BF infection, as detected by RT/PCR. In contrast, breeders given IBD inactivated oil-emulsion vaccine produced progenies more resistant to vaccinal IBDV infection in the BF and with poorer IBDV antibody serum conversion, as the high passive antibody titers may have neutralized vaccinal IBDV (intermediate strain) infection of the bursa. Moreover, the vaccination of chicks with high passive antibody titers may be less efficient. In conclusion, the broiler chickens from non-vaccinated hens showed a better serum conversion, beyond of the performance results at 40 days of age did not differ between the treatments.