Heliotrope contains toxins known as pyrrolizidine alkaloids that damage the liver, and is found particularly where there is bare ground like roadsides, fallowed ground and in stubbles.

Livestock tend to avoid it if other feed is available since it is relatively unpalatable.

While all animals are susceptible to heliotrope poisoning, sheep are primarily affected as they are most often grazed in locations where heliotrope is common.

British breed and cross-bred sheep are more commonly affected, more so than merinos due to their different grazing habits.

The toxin found in heliotrope alters the liver's metabolism for copper causing the liver to hold abnormally high levels of this element.

The liver damage caused by heliotrope is cumulative, so in other words, the liver damage increases each time an animal eats it.

When the liver becomes saturated with copper there is a rapid release of copper leading to kidney failure and death due to a condition commonly known as 'yellows'.

Yellows usually does not occur until sheep have been exposed to heliotrope for more than one summer, and often occurs after the exposure to heliotrope has gone when sheep are later put on lush pastures rich in copper, such as clover.

Although other livestock are susceptible to the effects of heliotrope, cattle and horses are more susceptible to heliotrope toxin than sheep.

Unlike sheep, the signs of liver damage associated with heliotrope poisoning often occur soon after cattle and horses are exposed to heliotrope and large losses of stock occasionally occur.