A recall has been issued for a product used to treat worms in sheep and MPI has issued a withholding period of 154 days before the affected animals can be slaughtered for food.
Animal health company Boehringer Ingelheim has recalled its Bionic Plus Hogget capsules, which treat worms in sheep.
New Zealand Food Safety deputy director general Vincent Arbuckle said the recall related to three batches of the product, about 219,000 capsules, which were dissolving too slowly in animals, making them less effective.
Arbuckle said MPI was told about the recall three weeks ago and had established a withholding period of 156 days to manage residues.
This meant farmers who want to send sheep and lambs to be killed now had to wait up to 22 weeks before they could send the stock to be killed for food.
That could result major financial headaches for some, if they could not meet contract requirements for the lambs' ages and had to pay to feed them until they could be killed.
Arbuckle said there was no food safety risk associated with the products.
"Boehringer Ingelheim has contacted both all vet clinics stocking Bionic Plus Hogget capsules to stop sale, and all customers who have purchased the product to stop use," he said.
"MPI continues to monitor the recall, and provide support where required."
Boehringer said it was working with Argenta Ltd which manufactures the product in Auckland and MPI to investigate the root cause of the problem.
Company spokesman Steve Rochester said the welfare of animals and its farmer customers was most important.
He said Boehringer Ingelheim has been working with vets and farmers to address the immediate welfare needs of animals and minimise the impact on farmers' businesses as much as possible.
"Through our veterinarian customers we have offered animal welfare support to affected farms by providing parasite control products for existing treated animals, as well as immediate financial relief for feed for hoggets destined for the meat market."
The company realised the product recall was a disruption for vets and their farmer customers during a busy time in the lambing season, he said.