Evaluation of Antibody Titer Changes against Newcastle Disease and in-fluenza (H9N2) In the Egg Yolk during Incubation Period and its Impact on The Replication of the Viruses

Maternal antibodies are transferred from hens to their offWinter through the egg yolk where the antibody is absorbed and enters the circulatory system. Passive immunity via maternal antibodies can lessen the effects of clinical diseases in chicks or prevent the incidence of them. Haemagglutination inhibition (HI) test is one of the popular assays for detection of Newcastle disease virus (NDV) and Avian influenza virus (AIV) infections. Newcastle disease and avian influenza disease are very important contagious infections which causes vast economic losses to poultry industry. In this study, antibody titres against NDV and AIV measured in serum of breeders, egg yolk, and day old chicks by HI method. NDV and AIV antibodies compared in serum of breeders and egg yolk of the flock. Level of antibodies in the first, third, 6th, 9th, 14th, and 18th days of incubation measured and compared. These values compared with antibody levels of day old chicks. In another experiment, NDV and AIV injected to eggs via allantoic cavity of eggs. EID50 test was used to compare the eggs with NDV and AIV antibodies and the eggs without antibodies (SPF eggs). There was no significant difference in NDV and AIV titres in serum of breeders and egg yolk samples (P>0.05). Also, antibody titres during incubation and serum of day old chicks showed no significant difference (P>0.05). Hence, evaluation of egg yolk antibodies is a valuable tool for estimation of antibody levels in serum of breeders and their chicks. Results of NDV EID50 test showed significant difference between eggs with NDV antibodies and SPF eggs (P<0.05). But, this comparison about AIV was non-significant (P>0.05). Hence, it is better to use SPF eggs for determination of EID50 of NDV.