A comparison of immune responses of broiler chickens to different methods of vaccination against Newcastle disease.

One-day-old broiler chicks from 4 groups of broiler breeder chickens were immunized by different methods of vaccination: 1) aerosol; 2) intratracheal; 3) drinking water; or 4) unvaccinated. The breeder flock from which the chicks were derived was vaccinated by one of the following methods: 1) a single injection of an oil-emulsion Newcastle disease virus (NDV) vaccine; 2) two vaccinations with oil-emulsion NDV vaccine; 3) vaccination with a live NDV vaccine; and 4) unvaccinated controls. Aerosol vaccination induced higher serologic responses than water and intratracheal vaccination, as well as giving the highest levels of protection against challenge. Mortality ranged from 20% to 66% in all eight groups of birds vaccinated intratracheally and challenged at 6 weeks of age. Results of challenge tests, in agreement with results of HI tests, further demonstrated that intratracheal vaccination at one day of age does not elicit a satisfactory immune response in birds with a maternal antibody titer of 15 or higher.

Immunization of broiler breeder chickens against Newcastle disease with an oil-emulsion vaccine.

Antibody response was rapid and high in broiler breeder chickens receiving 1 or 2 vaccinations with oil-emulsion vaccine against Newcastle disease at 23 or at 23 and 26 weeks old. The antibody titers remained high during the 41-week experimental period. At 64 weeks old, about 41 weeks after vaccination, the geometric mean hemagglutination-inhibition antibody titer was 67 from the single vaccination, and 103 from the double vaccination. The immune response to live-virus vaccine given at 2, 9, 20, 30, 42, or 54 weeks of age via the drinking water was high, but uniformity was lacking in the antibody response in the breeders and maternal antibody response in the progeny. Maternal antibody levels in one-day-old chicks were related to the titers of antibody in the dams. Maternal antibody titers of chicks originated from breeder flocks that were vaccinated with the oil-emulsion vaccine remained high for all hatches.

Interaction of aflatoxin with infectious bursal disease virus infection in young chickens.

Young White Leghorn chickens fed 2.5 microgram of aflatoxin (Afl) per g of diet from hatching until 4 weeks old and infected with infectious bursal disease virus (IBDV) at 3 weeks old had significantly higher mortality and more severely depressed body weights than chicks with aflatoxicosis or IBD alone. Afl-IBDV chicks also had more extensive gross and microscopic changes characteristic of IBD than did IBDV-chicks. None of the treatments significantly reduced antibody responses to Newcastle disease(ND) and infectious bronchitis vaccines or increased susceptibility to challenge with virulent NDV. In a similar experiment chickens fed Afl from hatching to 7 weeks of age had no marked depression in immune response to ND vaccination.