Even though the product was made available in the North Island for the first time, the company had expected sales to be down after last spring when the crop was implicated in hundreds of dairy cattle deaths in Southland and South Otago.
“Farmers have moved to growing fodder beet or kale for winter feed but there are still a lot of people growing HT swedes,” Green said.
“Although what happened last spring was very serious, we have farmers who have fed HT swedes for the past three or four years with no issues.
“We are still getting consistent feedback that this product is having the biggest positive impact on farming systems compared with anything else we have ever launched.”
HT (herbicide-tolerant) swedes have a genetic trait bred into them that allows the brassica to be sprayed with low-rate sulfonylurea herbicides. Little or no detectable spray residue can be found in the crop or in livestock after use.
Southern farmers have long had problems with wild turnip, fathen and other broadleaf weeds when growing winter crops, all of which are controlled by the sulfonylurea herbicide.
Green said PGG Wrightson Seeds was doing its own research into what might have gone wrong last spring and was growing plots of the swedes in Southland and Canterbury which will be fed to cows in the winter.
‘It’s really too difficult to establish a link with the problems from the spring as there are too many variables involved.’
Farmers who have bought the seed this season have had to sign a “product endorsement” which says cows died in the south from liver damage and most of the incidents occurred on HT swedes.
“Given our current state of understanding, PGG Wrightson Seeds recommends the prudent approach is that HT swede (HT-S57) should not be grazed by pregnant dairy cows,” the endorsement states.
Green said it was developed following consultation with Federated Farmers and DairyNZ.
“We just wanted to make sure that every single farmer who bought HT swede seed was aware of the issues.”
For Edendale contract milkers Logan and Melissa Johnson, the problems following feeding HT swedes have not gone away.
More than 20 cows died on the farm in spring from liver failure and about the same number from other causes they believed were linked.
“Just a couple of weeks ago we had a young cow that went downhill after a cold snap. We got the vet out to her and they said it was liver failure and to put the cow down,” Logan said.
Although they are still to do their final pregnancy scan, early scans show they will have an empty rate of about 15%.
“Usually we would be at 10% or under. The weather was rubbish during mating but we were giving them all the grass they could eat and had in the dairy a high energy blend so we were feeding them well.”
Production is so far 1% lower than last season when 660-670 cows were milked.
“We’re milking just under 700 so it’s disappointing that it’s down.
“We keep on having unexplained health issues. At the end of calving there were a lot of retained membranes and we still have cows that suddenly lose weight and we don’t know why. My gut feeling is it’s from the HT swedes.”
This year there is kale growing at the farm for late winter feed and their winter grazier is also growing kale.
VetSouth veterinarian Dr Mark Bryan said in-calf-rates on affected farms “were all over the place”.
“In some case there are good results and in others they’re very poor. It’s really too difficult to establish a link with the problems from the spring as there are too many variables involved,” Bryan said.
“From the facial eczema model in which cows also suffer liver damage, we know they are more likely to succumb to metabolic problems and don’t get in-calf. At the end of lactation they are more likely to be culled.”
He said he wished more farmers would take blood tests of cows which were sick and request liver tests of cows sent to the works.
“But it all costs money. A blood test can cost about $100 and in a low payout year I don’t blame farmers for not finding out what is wrong. It’s been a tough year for them.”
He said veterinarians nationwide would be on the lookout for similar problems with cows on brassica crops occurring this year.
“Last year we just thought at the start there were an unusual number of cases of acidosis and then we started testing and found out it wasn’t acidosis. It took a while to realise what was happening.
“It will be interesting to see what happens this year.”
DairyNZ regional Southland-South Otago regional leader Richard Kyte said results of the farmer survey were due and hopefully would give farmers some direction on winter feeding.
Late last year 120 Southland farmers were surveyed, half with cows which died or showed clinical signs and half which were unaffected.
“We asked questions on how the winter crops were grown, how animals were transitioned on to them and how they were fed. We’re hoping that there will be some common factors involved that we can tell farmers before winter.”
