NEW ZEALAND – A mystery condition which saw cattle experience ill health and in some instances die after grazing on swedes has been solved after a three month wait, according to Dairy New Zealand.
Deaths observed in Southland cattle in September have been caused by liver damage, officially linked to grazing on Swedes.
Baffled scientists got to work after notification of several deaths in dairy cows whilst grazing winter swede rotations.
Laboratory work revealed that substances known as pre-toxins containing sulphur, produced by all brassicas, become toxic in the rumen.
These nitriles are known to cause liver damage in rats. However, Dairy New Zealand stated that an “unknown toxin can’t be discounted.”
A spokesperson for Dairy New Zealand, the organisation overseeing the studies, likened the liver damage seen in Southland cows to that seen in outbreaks of facial eczema, with photosensitivity occurring after the liver has been damaged.
“We’ve reviewed the published scientific data on this topic," the spokesperson said. "It supports the possibility that substances in the swedes caused this disease.”
The spokesperson added: “While the study did not allow comparison between swede varieties, the findings indicate that cows experienced liver damage after grazing swede varieties as well as the herbicide tolerant variety, regardless of whether there were visible signs of illness.”
Dairy New Zealand said it has to be “careful” about drawing any major conclusions, offering sample diversity as a main reason to be tentative about the findings.
“The analysis is based on samples collected at a single point in time towards the end of the period when the illness was evident. They were not collected over the whole swede grazing period.
“Additionally, only a selection of swede varieties was represented in the animal samples taken.
Next is a more rigorous 120 farm survey to collate and analyse data, the collating process is near completion.
You can read more about the swede story by clicking here.
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