Farmers need to check for toxic rock fern in paddocks

Sunset at the paddock on Deep Creek Rd. Photo: Susanna Freymark

Local Land Services is urging livestock owners to be on the lookout for rock fern in their grazing paddocks.

Rock fern is a hardy plant that survives dry conditions and reshoots after rain and is most toxic when new fronds are reshooting or growing during autumn and winter.

The fern contains the toxin ptaquiloside. This toxin depresses bone marrow production of platelets and white blood cells in cattle which reduces the affected animal’s immune system and causes bleeding.

District veterinarian Dr Judy Ellem said we there had been a few cases of deaths in young cattle in the past few weeks in the Gunnedah district.

“These deaths are suspected to be caused by rock fern toxicity. Unfortunately, in most cases there has been multiple deaths,” said Dr Ellem.

“It takes two to four weeks before the effects of the toxin are seen in the animal, with recent affected animals being found dead in their paddocks. They have had blood from the nose and, or the anus.”

Landholders are asked to keep a close eye on their cattle and watch out for symptoms. Cattle that are affected by the toxin will be off colour, out on their own, and they may have a fever, or other signs of infection. They may have blood in their faeces, dark wine-coloured urine, or a nasal discharge.

Other signs can include heavy breathing, demonstrating weakness and swaying when walking. If examined closely there maybe spot bleeding in their mouth, gums, or eyes.

Sheep are also affected by rock fern, however, are more susceptible to a different toxin called thiaminase which destroys vitamin B1 or thiamine in the rumen.

“Sheep can be found dead, or they may be out on their own, appear blind, run into fences, or press against obstacles. They sometimes exhibit a syndrome called ‘stargazing’ where they have their head pointed upwards, or they may froth at the mouth and possibly seizure,” said Dr Ellem.

Horses are also susceptible to thiaminase toxicity, and can be seen to go off their food, become uncoordinated, they may carry their head low, be head nodding, ear twitching, yawning, and can also become excitable. Like sheep, they may also appear blind.

“Sheep and horses that are affected by the thiaminase can be treated with thiamine if found early enough,” she said.

If you have deaths or signs of toxicity in your livestock, please call your veterinarian for treatment and advice.

Rock fern in the paddock. Photo: Contributed
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