Rubber-vine (Crypto-stegia grandiflora) toxicity for ruminants

On one property in the restricted area of northern Queensland where rubber-vine is eaten by cattle the usual annual mortality was five out of 800 cattle mustered. This rose to 30 of 1000 cattle mustered when the rubber-vine had been burned the previous year. Some cattle in the field "drop dead" during exercise, usually after a short gallop or trot. Death is often sudden, with little or no struggling. Postmortem examination usually shows congestion and cyanosis of blood vessels, particularly the cerebral and myocardial vessels. Rubber-vine is present in the ruminai contents. Feeding trials with cattle showed that after fresh leaves had been minced, soaked in water for 16 hours and both leaves and extract introduced into the rumen, the lethal dose was as low as 0.7 g/kg body weight. Although the "dropping dead" syndrome was not reproduced in docile experimental cattle, it was reproduced in a paddock sheep which, over 3 days, received 10 g of minced rubber-vine leaves and their aqueous extract after soaking for 24 hours. The sheep collapsed after galloping 200 yards and died within a minute. Vet. Bull. 40: 310