Antithrombin-III activity in plasma of healthy and sick cattle.

Antithrombin-III (AT-III) activity was determined in the plasma of 32 healthy cows. The range of activities was between 105 and 160 per cent of a human reference plasma; the median activity was 132.5 per cent, and the 5 per cent and the 95 per cent quartiles were 111.1 per cent and 153.9 per cent of the standard. The activity of AT-III was also determined in 82 cows with a variety of internal diseases. In cows with hepatopathy, acute enteritis, generalised peritonitis, blood loss, idiopathic cardiomyopathy, glomerulonephritis and disseminated coagulopathy, the activity of AT-III was lower than in healthy animals. The lower values were due to decreased synthesis, increased consumption, or the loss of AT-III. An acquired deficiency of AT-III appears to favour the development of thrombophlebitis.