Avoiding residue failures and ensuring your milk is of the highest quality is crucial. So you need to be able to milk with confidence to positively promote the amazing product that is milk.

We don’t need to remind any of you of the media storm around livestock farming that has been building over the last months. A growing challenge lies in the future of demand for dairy products with the rise of nut, soya and cereal-based alternatives to dairy flooding the market.

We can offer a wealth of science to demonstrate the health benefits in comparison to the below par copycat products. Criticisms around the quality of the product is one of the most infuriating arguments posed at the dairy industry. Products such as ‘antibiotic free milk’ causes confusion to consumers who are unclear that ALL milk sold for human consumption is free from antibiotics.

Delivering a product that is of high quality, safe and free from any contaminants is absolutely critical to ensuring consumer confidence. Katie Fitz is going to take us briefly into the precautions taken by dairies.

What are residue failures?

All antibiotics that are allowed to be used in food producing animals have a Maximum Residue Limit (MRL). It is illegal to sell milk from an individual cow which contains medicines above this limit. Processor checks are carried out at various levels.

There are many reasons why residue failures may occur. Most commonly due to human error e.g. accidental transfer of milk from an animal under treatment, not withholding milk for the full withdrawal period or early calving cows. Other causes can be less obvious. This includes small volumes of highly contaminated milk left in the system if a separate dump line is not used, splashes onto the udder from topical treatments or mechanical failures such as leaking valves in the plant.

Who is responsible?

Ultimately, as the producer you are responsible for ensuring your product is free from residues. However, your vet is responsible for prescribing veterinary medicines and should ensure you are aware of the milk withdrawals. The milk withdrawal can be found on the data sheet. However, it only applies when a medicine is used ‘on licence’ as defined in the datasheet.

  • Medicines used ‘On licence’ must be:
  • In the defined species
  • For the defined condition
  • At the defined dose and duration

Some medicines are licenced to be used in combination and have a stated withdrawal. If using a non licenced combination, you should observe the longest withdrawal period; as long as non of the combination contain the same antibiotic. If they contain the same antibiotic then statutory withdrawal periods should be applied (E.g. Mastitis tubes containing penicillin given at the same time as Pen & Strep).

Sometimes, there is no appropriate course of treatment that is licenced for a particular condition. In these cases your vet can prescribe a treatment plan using the ‘medicines cascade’. This includes using a licenced treatment for a duration longer than on the licence. (For example Tetra Delta is licenced for one tube repeated at 24 to 48 hours in severe cases so twice daily administration or use for more than three days would be considered off licence). If medicines are prescribed on the cascade there is no defined withdrawal and your vet should set an appropriate period.

How can I reduce the risk of residue failures?

  1. Clear identification of cows under treatment and thorough records of duration of milk withdrawals are critical.
  2. Follow the instructions from your vet on withdrawal periods even if it differs from the time stated on the packaging as this may account for the product being used on the cascade. Delvo Test kits are available for use on farm and should be used in any uncertain cases.

This topic can be a real minefield. Therefore, if you are interested in learning more, book on to one of our Milk Sure Courses. As part of this, a farm specific assessment will help you minimise the risks and continue to send your milk with confidence.

Avoiding milk residue failures

Different Test Types

Immune Receptor Tests (e.g. Beta Star):

Quick tests that contain receptors that bind to specific antibiotics. The most commonly used ones look for beta-lactam antibiotics (such as penicillin and cephalosporins). However, more modern tests such as Randox InfiniPlex can detect up to 42 different medicines including flukicides and non-steroidals such as Metacam. These tests are available commercially and are increasingly being used to help pinpoint the reason for bulk tank failures.

Inhibitory Tests (e.g. Delvo T):

These tests include wells that contain bacterial spores and a colour changing indicator. When milk is added to the well the colour is purple. The sample is incubated and the bacteria should grow causing a colour change to yellow. If antibiotics are present the bacteria do not grow so the samples remains a purple colour. These tests can detect a larger range of antibiotics but can take 3 – 3.5 hours to complete.

Liquid Chromatography Mass Spectroscopy:

This test is used by the Veterinary Medicines Directorate to check final product safety; but can also be used by dairies to investigate bulk tank failures. It detects all the compounds contained within a sample of milk. So can detect the presence of any compound within the milk including non steroidals, flukicides and disinfectants.