Abstract: Eighteen blood biochemical indexes were tested in ducks experimentally infected with a highly pathogenic avian influenza virus, A/duck/Guangdong/220/2004(H5N1) by intravenous and eyes-nares-mouth-cloaca routes. The results showed that the activity or contents of serum alanine aminotransferase（glutamic-pyruvic transminase）, aspartate aminotransferase（glutamic-oxaloacetic transminase）, γ-glutamyltransferase, creatine kinase, lactate dehydrogenase were significantly increased; alkaline phosphatase’s were obviously decreased; early α-Amylase’s were significantly increased, late slightly decreased; total protein, globin, urea nitrogen, cholesterol, calcium and phosphorus’s were somewhat increased; albumin, creatinine, glucose, triglycerides and uric acid’s were usually decreased. We consider that assaying these blood biochemical indexes are useful for diagnosing avian influenza.

Key words: H5N1 subtype avian influenza; blood biochemistry; ducks