The Green Party is again calling for the ban of HT swedes, following two cows becoming ill as a result of eating swedes.
In 2014, 200 Southland dairy cows and 300 ewes died after eating herbicide tolerant (HT) swedes.
DairyNZ has updated its winter feed transitioning advisory to say that in 2017, there have been two farms experiencing ill-health with cows on swedes.
Green Party pesticide spokesman Steffan Browning called for Minister for Primary Industries Nathan Guy to immediately order the removal of the swedes from the market.
“It’s extraordinary they’re still being sold. They should have been taken off the market back in 2015 when tests showed that HT swedes caused liver damage in livestock.”
Browning said the Government had limited its action to advising farmers of when to feed the swedes to cattle, but it clearly had not worked.
DairyNZ’s recommendations for feeding the brassicas to cows include not feeding HT swedes on the milking platform in late August/early September, as it is the period is when many of the factors that lead to ill-health and potential cow death can rapidly combine.
Animals being fed the swedes in autumn, before the first frosts, were likely to eat leaves instead of the bulbs as they were harder to eat.
“Be cautious, at any time during the season, when grazing animals on swede crops with a high leaf to bulb ratio as cows may preferentially graze leaf,” the advisory says.
DairyNZ also advised farmers not to feed swede crops while they were in their reproductive growth phase.
VetSouth Winton veterinarian and director Mark Bryan said as far as he was aware there had been three events in Southland and Otago that all involved HT swedes.
Bryan was involved with further analysis of the damage the swedes caused to the livers of cows, and found the climactic conditions of 2014 caused unusual growth patterns. A report he did linked high glucosinolate levels in the leaves of the swedes.
“It’s very similar to 2014, it’s been a warm May and so there’s been quite a lot of growth. There hasn’t been many frosts. I think it is quite similar to what it was happening in 2014 in terms of climate.”
However, he said far fewer HT swedes had been planted than in Southland and Otago since the original event, but given that, the new events were a worry.
“Even if it’s as severe on the affected farms as last time it won’t be as severe because there isn’t as much of it around.”
HT swedes are sold through PGG Wrightson Seeds.
PGG Wrightson Seeds and Grain general manager John McKenzie said he did not want to comment further on the situation, citing DairyNZ’s advice.
However, he did say there had been fewer sales of HT swede products in the past few years.
PGG Wrightson Seeds sells the product under a product endorsement that it is not recommended to be fed to lactating or pregnant dairy cows.