DICOUMAROL STUDIES: I. ORAL ADMINISTRATION OF SYNTHETIC DICOUMAROL TO VARIOUS CLASSES OF SHEEP AND CATTLE

In one experiment 3 steers, 4 bull calves and 4 wether lambs were orally administered 2 milligrams dicoumarol per kilogram body weight and blood-clotting time measurements were made over a 4-day period. All animals responded to the dicoumarol but differences were evident between sheep and cattle; sheep were apparently more tolerant of the drug.The ’one-stage prothrombin’ test was more reliable and sensitive than the clotting tests employed for factor VII, factor X and prothrombin concentration.In a second experiment, 16 ewes in late pregnancy were fed rations containing 0 to 30 p.p.m. of synthetic dicoumarol and vitamin K 3 as a cross treatment. Evidence of abnormal clotting power of ewe blood was observed in ewes fed diets containing 10 p.p.m. of dicoumarol. There was some indication of cumulative effects at this level after 32 days on test. At intake levels of 20 and 30 p.p.m. clotting times were affected more markedly and some ewes exhibited extended bleeding times after 2 to 4 weeks on test. No unusual hemorrhaging occurred at parturition. In general, the lambs’ blood did not reflect the pre- or post-partum dicoumarol intake of their mothers but a few lambs, as in the case of the ewes, exhibited low tolerance for dicoumarol without showing much disturbance in terms of clotting time. A large single oral dose of menadione sodium bisulphite demonstrated the effectiveness of vitamin K 3 as an antidote. However, vitamin K 3 as a ration supplement at 12 milligrams per pound feed failed to protect ewes against the effects of dicoumarol.