To study the effects of different doses of furosemide on the urinary excretion of water and electrolytes 16 healthy steers were used. The animals were randomly divided into four groups and treated, intravenously, as follow: control (10mL of isotonic saline); 1; 2 and 3mg kg-1 BW of furosemide. For the next 4h, the urinary volume was measured and blood samples were taken to calculate the urinary excretion ratio. Furosemide increased the urinary volume by four fold, with higher effect with 2 and 3mg than 1mg, mainly in the 1st and 2nd hour of treatment. Furosemide did not change the glomerular filtration rate, but decreased significantly the tubular reabsortion of water, sodium, and at lower level of potassium, causing the diuresis. The osmolality was decreased about 28% in either doses of furosemide. For practical use 2mg kg-1 BW of furosemide should be adopted for diuretic effect in cattle.
furosemide; cattle; urinary excretion; electrolytes
