Farmers who inadvertently fed their calves milk contaminated with the potentially harmful bacteria, Clostridium botulinum, are being told the risk to their animals' health is low.
Calf feed milk replacer is the calf equivalent of infant milk formula.
Fonterra's animal feed subsidiary, NZAgbiz, has recalled 65 tonnes of Ancalf and Brown Bag calf milk replacers.
It contains the same contaminated whey protein as in infant formula and other products being recalled around the world.
NZAgbiz believes the nearly all the product, about 60 tonnes, is still on the shelves and not out on the farm.
General manager Justine Pearce says she's been working with rural retailers to identify farmers who have bought contaminated stock.
Ms Pearce says NZAgbiz doesn't know yet whether the strain of the bacteria Fonterra has found would be a direct threat to the calves but it's putting safety first.