Hemato-clinical changes in phenylhydrazine-induced acute hemolytic anaemia in calves.

Acute anaemia was induced in calves aged 1 week, using the oxidant chemical phenylhydrazine-hydrochloride (PHH). The hematoclinical responses to graded doses were evaluated. Mild anaemia was observed with the 60 mg/kg body weight (B.W.) dose. The 100 mg/kg B.W. dose was too toxic. The sublethal 80 mg/kg B.W. dose produced the desired type of hemolytic anaemia, the peak of which being observed on d 4 post-injection (p.i.). Hemolytic anaemia was evidenced by hemoglobinaemia and hemoglobinuria. The acute toxicity symptoms lasted for about 30 min. Thereafter, the animals appeared to overcome the stress. In general, increases in pulse and respiration coincided with progress of the hemolytic syndrome. Peak response occurred 48 to 60 h p.i.