There have been reports of more dairy cow deaths in Southland as farmers switch their cows from pasture to winter crops.
Farmers have recently been given detailed advice about managing swedes in their cows' diets, following hundreds of cattle deaths last spring linked to the brassica.
Now there are warnings from DairyNZ and vets about safeguarding the health of cows being fed the increasingly popular winter vegetable crop fodder beet.
DairyNZ regional leader for Southland and South Otago Richard Kyte said around half a million cows in the region had been moved onto winter crops and vets had already reported a small number of deaths and cows falling ill.
Mr Kyte said fodder beet posed different risks to swedes but still had to be carefully managed.
"Fodder beet's been taken up rapidly in the south. It's a great form of winter feed, but it also comes with its challenges as well, around how you feed it.
"Acidosis is an issue, so if you don't transition it well you can create ill health with your cows, or if they break out onto it, you've got to be vigilant, making sure they get the right amount and the right amount of other supplementary feed, along side it.
"It's around the change of diet, making sure it's not a rapid change, it's a gradual change of diet onto the new crop."
DairyNZ is asking vets and farmers to report cases of ill health in cows so it can assess the extent of the issue.