Abstract
Background: Newcastle disease (ND) is a viral disease that affects numerous bird species and is still present in many places, including Iraq.
Aim: The purpose of this study was to compare maternal derived antibodies (MatAb) against ND vaccination in one-day-old imported Cobb 500 and Ross 308 chicks.
Methods: From April to October 2020, four locations in Mosul governorate chosen to compute the maternal derived antibodies (MatAb) from one-day old broiler chicks. Seven hundred and seven blood samples (451) from imported 28 Ross 308 flocks and 256 from 17 Cobb 500 flocks were obtained and tested for antibody levels using an indirect ELISA (iELISA) assay (Biochek commercial kit, UK).
Results: The Cobb 500 broiler chicks outperformed the Ross 308 broiler chicks in that all of the Cobb 500 broiler chicks had maternal antibody (Mat Ab) titers (100% positivity) versus 97.78% of the Ross 308 chicks, had a mean (Mat Ab) titer of 9871.47 versus 8647.76, and had a mean CV percentage of 12.41% versus15.18% respectively. The mean Vaccination index of Cobb 500 broiler chicks was 966.59 versus 821.60 for Ross 308 broiler chicks.
Conclusion: Although both broiler types produced chicks with high and uniform maternal antibody titers, Cobb 500 produced chicks with higher protective titers than Ross 308.

Key words: Cobb 500, maternal antibody titers, Newcastle disease, Ross 308.