Grass tree poisoning
Grass trees and yacca are common names given to plants belonging to the genus Xanthorrhoea. These plants, with their long flower spikes, are capable of causing a peculiar disease often called 'crampy wamps', 'staggers' or 'rickets'.
Cattle lose condition and develop an unusual staggering lurch to one side after eating the plants. Surprisingly, they often seem normal until forced to move in any direction other than a straight line.
As the condition worsens, and they become poorer and stagger more, they often fall and are sometimes unable to rise. Once this occurs, the animal rapidly wastes away and dies. Affected cattle may also become worse 2-3 weeks after they have stopped eating the plant.
Another common sign of this disease is the continuous dribbling of urine with the tail held high. In some cases, complete or partial blindness has occurred, caused by cataracts in the eyes. It is not known whether this is a result of grass tree poisoning.
One curious feature of toxicity is delayed onset of clinical signs. Several sources report delays of up to 6, 10 or 12 weeks after the animal's last access to Xanthorrhoea plants.
Conditions for poisoning
Access to grass trees, especially when they are flowering and other feed is scarce, usually allows poisoning to occur. In South East Queensland, this is usually in winter and spring; however, in North Queensland, grass tree poisoning is common in autumn and early winter.
Cattle are the only animals affected and the flowering spike or spear seems to be the most poisonous part of the plant.
Newly introduced cattle and those grazing on mineral-deficient country with grass trees are especially likely to be affected.
Remove the affected animals from the paddock. Unless the signs are very severe, cattle will completely recover when removed from the area. If clinical signs are severe, consult a veterinarian.
It is claimed that supplementary feed, especially protein and salt, can prevent the disease but there is no definite evidence of this. Discuss supplementation options with your local stock inspector, beef advisor or veterinarian.