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AgVetLink: Number 63, August 2007

Milk Dilution Withholding Period Policy

Until now, when setting withholding periods (WHPs) for veterinary medicines used on lactating dairy cows producing milk for human consumption, the policy has been to set WHPs based on milk at the farm gate. The new policy, which was finalised recently, provides guidance on the circumstances when milk dilution within the herd could be an additional option when setting WHPs.

Risk management

When considering the risk management options under the ACVM Act, having the milk WHP based on an entire herd treatment is not appropriate in some cases. Furthermore, the ACVM Group must take into account risks and benefits along with ensuring there is least cost to the public. The current risk management approach has the potential to unnecessarily increase the total cost (based on cost of product and lost income from discarded milk) of some treatment options to the veterinarian and farmer when managing the welfare of animals.

Veterinarians and end users

Consequently, the new policy was developed to provide more flexibility and takes into consideration the role of key risk managers and level of compliance with the risk management tool. Veterinarians play an important role as risk managers and the ACVM Group’s expectation is that veterinarians will provide clear advice to end users to enable them to comply with legal milk residue requirements. If end users do not comply with this advice, then (as has always been the case) they may be subject to compliance action.

Limited treatment

The policy, which allows dilution of milk containing residues within the herd where use is limited to a small proportion of the herd, is consistent with good veterinary/agricultural practice in New Zealand. It will not apply to veterinary medicines where there is potential for whole herd treatment in usual circumstances. Product types likely to fit the new policy would include veterinary medicines with restricted use patterns, such as those used to treat occasional sick animals, eg non-steroidal anti-inflammatory drugs, antihistamines and sedatives.

It is expected that no greater than 10% of the herd would ever be likely to be treated with such products and this is the maximum percentage that would be considered for limited treatment within a herd for this policy. The value of 10% has been considered as it allows for ease of calculation and understanding by the product user.

Additional option

Withholding period statements would be modified to give this option along with the standard WHP which is based on entire herd treatment. It is important to recognise this milk dilution policy does not replace standard WHPs, but is an additional option for the risk managers to consider when treating animals.

Consultation

Key stakeholders, including Federated Farmers, the dairy industry and the New Zealand Veterinary Association, were consulted about the proposed policy. While there was some initial lack of understanding of the rationale for the policy and its implications, once these were clarified there was general acceptance of the policy.

Concern about antibiotics

However, a number of key stakeholders were uncomfortable for antibiotics to be included in this policy. The ACVM Group agreed not to include this group of compounds, but emphasised that the policy could apply to certain antibiotics as it believed residues and antibiotic resistance would not be compromised by the policy.

Following a second round of consultation on the milk dilution policy, the ACVM Group received a number of submissions from stakeholders. The submissions all expressed support for the policy for non-antibiotic drugs where there would be clear welfare benefits, but there was a general lack of confidence that the policy would be able to manage risks associated with the use of antibiotics.

The concerns regarding increased use leading to antibiotic resistance are considered to be minimal by the ACVM Group. However, considering the level of concern expressed by stakeholders, the ACVM Group has implemented the policy with the exclusion of antibiotics at this time.

No change to MRLs

The policy did not propose any changes to the permissible maximum residue limits, which also manage microbiological effects in humans. The management of antimicrobial resistance does not rely on economic factors, such as the cost of discarded milk, to control use. Any increase in use would be monitored through the usual monitoring of antibiotic sales by the ACVM Group.

Residue testing

Concern was raised regarding the testing for residues of the non-antibiotic products as they are often not part of routine checks. While the increase in levels in the milk is not expected to be significant, the ACVM Group will consider all changes to use when testing programmes are set up.

The policy is available on the ACVM website (http://www.nzfsa.govt.nz/acvm/index.htm).