This study was designed to find out the effects on haematology (Hb, TLC and DLC), immune response (against NDV vaccine) and on organ body weight indices (liver, spleen, bursa of Fabricius and thymus) in broiler chickens when given two different HPS vaccines (Formalinized and oil-based HPS vaccines). Morbid livers of chickens affected with naturally occurred hydropericardium syndrome (HPS) were collected from field outbreaks to prepare the HPS vaccines and inoculum. Sixty broiler chicks were divided into three groups (A, B and C), comprising of 20 chicks in each on 10th day of experiment. At 14th day of age, chickens of groups A and B were given f-HPS and o-HPS vaccines, while group C was kept as unvaccinated control. On 28th day of age chickens of groups A, B and C were challenged with HPS inoculum. To study the effects of f-HPS and o-HPS vaccines, blood samples were collected on 12th (pre-vaccination), 26th (postvaccination) and 35th (post-challenge) day of experiment.

Haematological study revealed that f-HPS and o-HPS vaccines had no significant effects on haemoglobin concentration in groups A and B, but its concentration decreased significantly on 35th day in control group-C. Whereas TLC values increased significantly on 26th and 35th day in groups A and B, but decreased significantly on 35th day in group-C. DLC value revealed that there was relative lymphocytosis and heterpenia on 26th and 35th day in groups A and B, whereas eosinophilia on 35th day. While in control group-C there was lymphopenia and eosinopenia along with hetrophHia on 35th day. Antibody titre against Newcastle disease virus vaccine indicated that there was no significant difference in'GMHI titre values among the groups A, B and C. Results of organ body weight indices indicated that in control group-C (unvaccinated) indices of liver, spleen and bursa of Fabricius were significantly higher than those of groups A and B, whereas no effect was observed on thymic body weight index among groups A, B and C.

The results of this study suggested that f-HPS and o-HPS vaccines had no significant effect on Hb concentration, TLC and DLC values. No significant immuno-modulatory effect was noted on antibody titre against NDV vaccine of these HPS vaccines, whereas significant effect was noted on organ body weight indices of livers, spleen and bursa of Fabricius in group-C as compared to vaccinated groups.