About withholding periods for vet medicines
If a veterinary medicine has been used in or on an animal, you must wait a minimum amount of time before it is used for food. This is to make sure the medicine won't pose a health risk to consumers.
Veterinary medicines registered for use in or on animals must have the withholding period printed on the label. We calculate withholding periods from residue data provided during registration of a veterinary medicine.
Determining residue withholding periods for veterinary medicines - ACVM registration standard and guideline [PDF, 148 KB]
Default withholding periods for veterinary medicines
In some cases, where no residue data is provided for a product, default withholding periods are used.
The following default withholding periods are applied to registration of veterinary medicines without residue data. These are conservative withholding periods based on all residue data provided to MPI.
These don't apply to sustained release formulations because a withholding period must be after release into the animal, not after the medicine is given to the animal.
Birds, including chickens
Meat: 63 days
Eggs: 10 days
Ruminants, including deer, cattle, sheep
Meat: 91 days
Milk: 35 days
Camelids, including llama, alpaca
Meat: 63 days
Lagomorpha, including hares, rabbits
Meat: 63 days
Monogastrics, including pigs, horses
Meat: 63 days
Fish and shellfish, including crustaceans, molluscs
Meat: 35 days
Milk withholding period based on dilution
There is a direct relationship between the residues present in milk after an animal is treated with a veterinary medicine and the amount of milk that animal produces. Because of this, residues present in the milk of a few treated animals in a herd can be diluted when milk from treated animals is mixed with milk from untreated animals.
Under current ACVM policy, we will consider allocating a milk withholding period (WHP) based on dilution for veterinary medicines when all the following situations apply:
- Treatment of a small proportion of the herd is consistent with good agricultural practice. Products generally administered on a whole herd basis – for example, parasiticides – are not eligible.
- No more than 10% of the herd is treated.
- The veterinary medicine does not contain an antibiotic.
- Use of the product has veterinary oversight, in other words, it is a restricted veterinary medicine.
All applications will be considered on a case-by-case basis.
Where approved, the veterinary medicine will have 2 withholding periods stated on the label:
- the standard withholding period, and
- the dilution withholding period, which accounts for dilution of residues from treated cows with milk from untreated cows.
The label will stipulate under which circumstances the dilution WHP may be applied. The veterinarian will then be responsible for advising the farmer whether to apply the standard or dilution WHP and completing the required records of this decision.
