Comparative Haematology and Serum Biochemical Responses of Two Chicken Hybrids following Newcastle Disease Virus Infection

Newcastle disease (ND) remains one of the most significant viral threats to poultry production worldwide. This study evaluated the haematological and serum biochemical responses of two commercial breeds: Dominant Black (DB) and Isa Brown (IB) pullets, following experimental infection with a velogenic Newcastle disease virus (KUDU 113 strain). A total of 120 ten-week old pullets were randomly assigned into four groups: DB-infected, DB-control, IB-infected, and IB-control. Birds in infected groups received 0.1 mL of 10^6.4 EID₅₀ of the virus intramuscularly, while controls received phosphate-buffered saline. Blood samples were collected before inoculation and on day 4 post-infection for haematology and serum biochemistry. Results showed significant (P < 0.05) reductions in packed cell volume, haemoglobin concentration, erythrocyte count, and total leukocyte count in infected groups compared with controls. Differential counts also revealed decreases in heterophils, lymphocytes, and monocytes relative to the controls. Serum total protein, albumin, and globulin concentrations were also significantly (P < 0.05) reduced. The anaemia observed was normocytic and hypochromic, suggesting acute blood loss and intravascular haemolysis, while leucopenia and hypoproteinaemia may indicate immunosuppression or liver dysfunction. No significant differences were observed between DB and IB pullets, indicating similar in susceptibility. This aligned with the gross and histopathological lesions, previously reported for these same experimental groups, where absence of breed-related differences in susceptibility was consistent for the two breeds. These findings highlight the profound disruption of blood and biochemical parameters caused by KUDU 113 NDV and reinforced the need for integrated control strategies that go beyond vaccination to include improved nutrition, stress reduction, and strict biosecurity.