We recently attended an unusual and devastating case of suspected plant toxicity in our area. We were called out one weekend to a farmer who had lost a number of head of adult cattle the previous day and had several cows now down and unable to get up. The cattle had been let out onto a fresh, recently fertilised kikuyu pasture after being yarded overnight. On the basis of the clinical presentation of the cows and the results of lab tests a diagnosis of suspected kikuyu poisoning was made.
Kikuyu is a common pasture, especially in more coastal areas with higher rainfall and warmer climates, but is still grown and grazed in this region. It is generally grazed with no ill effect, but sporadic outbreaks of kikuyu poisoning have been documented in Australia, New Zealand and Africa.
The exact cause of kikuyu poisoning is unknown, despite several investigations into the cause, the clinical symptoms can vary a little also. Some of the more commonly seen symptoms of kikuyu toxicity include: sudden death, recumbency, watery bloat, salivation, incoordination, depression, dehydration, kidney failure, rapid heart rate and rapid shallow breathing. Kikuyu can be quite high in oxalates, which may cause kidney damage and possibly irritate the mouth cavity and guts leading to increased salivation and bloat, but this has not been proven. It has also been postulated that certain fungal infestations may make kikuyu more toxic, however again this has not been proven.
There are some risk factors that some outbreaks have had in common. Kikuyu poisoning usually occurs in rapidly growing pasture in autumn, often following rain. The majority of offending pastures have been recently spelled and fertilised. A number of, but not all cases, of poisoning have been associated with a recent attack by army worms. Varying species of fungi have also been detected in toxic kikuyu pastures, but there hasn’t been one species in particular implicated in every poisoning.
Kikuyu poisoning is thankfully not a common poisoning, but it unfortunately is very often lethal to affected cattle and devastating to affected farmers. Until the exact cause is determined it is difficult to provide accurate advice on avoiding toxicity, but avoiding grazing stressed, recently fertilised kikuyu pastures during autumn may help.