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18/05/2014 08:53 BST | Updated 18/05/2014 08:59 BST

Australian Sheep 'Cracking Their Heads Open' After Eating Poisonous Plant, Darling Pea

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A plague of a poisonous plant in Australia is turning sheep suicidal causing the crazed beasts to crack their own heads open.

The darling pea plant is toxic to animals and if grazed on over a period of time causes addiction, lack of coordination and depression.

Farmers Stephen and Louise Knight have lost 800 sheep in such a manner in New South Wales.

Louise said: "They just go to a post and bang their head on it till they crack their heads open; it's like dealing with a thousand heroin addicts."

The toxin works by blocking an enzyme involved in metabolism leading to weight loss and erratic behaviour "similar to that of a drunk."

There is no cure for the affliction other than trying to ween the sheep off it.

A vet from the affected region, Bob McKinnon, said: "Once you take them off it they are no longer exposed to the substance that is blocking the enzyme and the cells can then repair themselves.

"But if they've been on it too long the damage has been done and it doesn't repair to where it should be."