The aim of this study was to evaluate the changes that occur in the acute phase response (APR) of experimentally-induced salmonellosis in buffalo calves and to identify potential indicators of infection. Five buffalo calves received 10⁹ colony-forming units of Salmonella typhimurium, orally. Another five animals were used as control group. Clinical examinations were performed and venous blood was sampled before and throughout 7 days after inoculation. Red blood cell count (RBC), packed cell volume (PCV), hemoglobin (Hb), plasma fibrinogen, serum haptoglobin, ceruloplasmin, transferrin and iron were measured. Severe diarrhea started 72-108 h after inoculation, in all animals. The infectious stimulus induced severe APR, characterized by pyrexia, lymphopenia (4.99±1.73x10⁹ cells/L), increase in fibrinogen (24.7±4.91 µmol/L), haptoglobin (21.5±8.65 µmol/L) and ceruloplasmin (1370±374 mg/L), decreased transferrin concentration (3.90±0.69 g/L) and hypoferremia (15.2±11.2 µmol/L). These changes coincided with the onset of clinical signs. Alterations of lower intensity occurred in erythrogram. Based on the magnitude and duration of changes, it is suggested that the combined measurement of serum levels of iron and haptoglobin is a useful tool for identifying newborn buffaloes recently affected by bacterial disease and for monitoring the effectiveness of its treatment.

Key words: Acute phase proteins, Buffalo calves, Diarrhea, Salmonella typhimurium