The deaths of 22 quarter horses on a property in Queensland was caused by a type of grass, independent analysis suggests.
The horses died within a few days of each other last October on the property southwest of Brisbane, at Kooralbyn.
Biosecurity Queensland launched an inquiry and indicated botulism or scrub ticks were most likely responsible for the deaths.
Agricultural scientist Kerry Marsh was engaged by the horses’ owners to delve further.
She sent hair samples from two of the three surviving horses to the United States for testing.
Evidence suggests the horses were casualties of johnson grass, which can become stressed in certain conditions, resulting in a rise in cyanide levels.
The symptoms shown by the horses before their deaths were consistent with cyanide poisoning.
Those responsible for the care of the horses suspected the grass following the deaths and burnt off the pasture.