The herbicide-tolerant winter fodder crop was implicated in the deaths of more than 200 cows in the south in spring. Glucosinolate, a naturally occurring compound found in almost all brassicas, was blamed for causing liver and kidney damage.
“So far we’ve seen no change in sales but farmers are usually planting winter crops in November and December in the south and they usually buy the seed as they sow it so we won’t have a good picture yet of what is happening,” Green said.
“Many famers have told us they grew really good crops of HT Swedes last season with no concerns and will plant it again. Others have had problems.”
Deaths also occurred on other brassica crops.
The seed company, along with vets and representatives from Federated Farmers and the Ministry for Primary Industries, is part of a working group organised by DairyNZ to explore the reasons for the cattle deaths. It is working towards setting up trials in Canterbury, where it has research facilities, as well as in Southland this season.
‘The more we look into it the more we realise just how little of the science of it all we understand.’
“We want to try to understand the triggers of what caused the high levels of glucosinolates so we will grow the crops in extremely controlled environments.
He said the first step would be finding a robust testing method for glucosinolates.
“I’m not a scientist but I understand there are 120 of these compounds and between 10 and 15 of them cause animal health issues, but we don’t know at what levels and how they interact with each other.
“The more we look into it the more we realise just how little of the science of it all we understand.”
The DairyNZ working group has also started talking to farmers to build up a detailed picture of what happened during spring.
About 120 farmers, both affected and unaffected, are being interviewed by a team of 10 people, who are asking them about their farm management practices, cropping and fertiliser history, and climatic growing conditions during the past season.
“We need to understand the wide ranging factors that may have contributed to the outbreak of swede poisoning,” DairyNZ’s general manager for extension Craig McBeth said.
“These include climate, soil type, trace minerals status and fertiliser programmes. All these factors can influence the levels of several natural compounds found in brassicas that can make them toxic.”
DairyNZ has also sent samples collected from a number of swede varieties for testing.
McBeth said they did not expect any results back from the crop testing until February.
