How our milk is tested for antibiotics

Milk testing

Yesterday, I explained why and how we use antibiotics to treat a cow who falls ill in the herd, together with what we do to make sure no antibiotics get in the milk that leaves the farm.

In this post, Fonterra’s quality manager for milk supply, Sarah Carter, answered a few questions about how the milk is screened for antibiotics by the milk factory.

MMM: Why is it important to keep antibiotics out of milk?
SC: Customers, consumers and markets have very clear requirements that dairy products are to be free of antibiotic residues. The two main reasons for this are: the risk of causing allergic reactions in humans (e.g. from penicillin), and the concern about a build-up of antibiotic resistance as a result of consumption of dairy products containing low levels of antibiotics.

MMM: What does the law say about antibiotics in milk?
SC: In Australia, the Australian Pesticides & Veterinary Medicines Authority (APVMA) assesses agricultural and veterinary chemicals, such as cattle antibiotics, as being suitable and safe for use. They set Maximum Residue Limits (MRLs) after undertaking a thorough evaluation, including a dietary exposure assessment. These MRLs apply to domestically-produced foods, and are set well below the level at which any residues would be harmful to human health. The MRLs are set at levels which are not likely to be exceeded if the approved label instructions on the antibiotic product are correctly followed.

MMM: How and when is the milk tested?
SC: Most, if not all, dairy companies test tankers of milk for antibiotics prior to unloading at the factory, to avoid any contaminated milk entering the supply chain.

A number of dairy companies will also have the individual farm milk samples randomly tested during each month to further discourage farmers from taking a risk and allowing a vat-load of milk to be collected where perhaps a treated cow had been accidentally milked.

At Fonterra, we have both these measures in places – we are very clear that to maintain and build the market relevance of our dairy products, dilution with milk from other farms in the tanker is not the solution.

MMM: How sensitive are the tests?
SC: There is quite a wide range of tests available to detect antibiotics in milk, and the detection limits for antibiotics vary between tests. All dairy companies have their antibiotic testing procedures audited by the relevant state dairy regulatory authority (such as Dairy Food Safety Victoria) to ensure that their chosen test method is suitable for purpose and based on a risk assessment.

Different test methods will have different sensitivities to the various active ingredients found in commonly-used antibiotics – there is a technical information note available on the DFSV website which lists the common tests and their detection limits.

MMM: What happens if antibiotic residues are detected?
SC: If antibiotics are detected at the tanker level (prior to unloading into the factory), the entire tanker load is rejected and the milk disposed of (e.g. via the factory environmental management system).

Traceback testing is undertaken on all farms on that tanker load, to identify the source of the issue. We then undertake an on-farm investigation to get to the root cause of the problem and put measures in place to ensure it doesn’t happen again. All antibiotic-positive tankers must be reported to the state dairy regulatory authority, and followed up with a report stating the findings of the on-farm investigation.

If antibiotics are detected on a random farm sample test, we again undertake the on-farm investigation to help the farmer identify what went wrong. We also undertake a trace-forward to check for any impacts to products manufactured from this milk.

Farmers receive a penalty for supplying antibiotic-contaminated milk, and this penalty increases significantly if it happens again – fortunately, repeat offenders are incredibly rare, which demonstrates that the investigation and corrective action process achieves what it’s meant to.

At Fonterra we also encourage our farmers to get in touch with our SupportCrew milk quality specialists, who can assist farmers with advice and support to minimise the risk of mastitis in the first place.

Thanks Sarah!

Mastitis, antibiotics and milk

Why do we use antibiotics on our farm? Very simply, because despite everything we do to look after their well being, cows, just like people, sometimes fall ill and need antibiotics to get better.

It’s very rare that any of our 260 milking cows become lame with an infection while digestive problems are almost unheard of here and, in any case, do not require antibiotics.

The number one illness we treat on our farm is mastitis. If you’ve breastfed a baby yourself, there’s a fair chance you’ve experienced mastitis. In both cows and women, the symptoms include swelling, warmth and redness for light cases. Nasty cases bring flu-like symptoms that, in cows, can progress to become extremely serious.

How we prevent mastitis
So, how do we reduce the incidence of mastitis on the farm? We begin even before the calf is conceived by selecting sires whose daughters show a naturally lower susceptibility to mastitis.

At the same time, we minimise the risk of infection by keeping the cows and their environment as clean as possible. Tracks are maintained so there’s less mud around to flick onto teats and cows are happy to walk straight to their grassy paddocks rather than spending their rest times on mucky surfaces.

Cows resting in the paddock

Cows resting in the paddock after milking

The cows are well fed with a carefully balanced diet that is mostly grass and we treat the cows with care to minimise stress. It’s a slow, gentle walk to the milking shed, there’s no shouting and if I see one of our cows run, there’d better be a good explanation!

The hygiene of the dairy is important, too. We clean any dirty teats before the milking machine cups go on and spray them afterwards with a mix of iodine and glycerine to disinfect and protect them. We also routinely test the milking machines to make sure they are gentle and effective.

And we’re vigilant. Not surprisingly, when you spend hours every day with the cows’ udders at face level, you notice a sore cow quite quickly. A sore cow is an unhappy cow and an unhappy cow is an unhappy milker, too. Everyone who milks in the dairy has been specially trained at a “Cups On, Cups Off” course to look for mastitis and put top priority on the comfort of our cows.

Sometimes, cows have sub-clinical infections that don’t show any symptoms, so every few weeks, we collect samples of milk from every cow and have them analysed at the local herd test centre lab.

It’s a lot of work but it’s important work. The comfort of the cows is our number one priority and there are implications for the quality of the milk, too. If there is too much mastitis in the herd, our milk has a shorter shelf life.

One thing we don’t do, however, is include antibiotics in the cows’ feed. Routine antibiotic use is not legal and would mean that none of our milk would be useable.

Treating mastitis
When we find a cow with mastitis, we don’t wait to see whether she goes downhill, we treat her immediately with the medicine prescribed by (and only available from) our vets to help her recover fast. Antibiotics help the cow feel better in a day and we keep on milking her so that her udder is well drained and kept as soft as possible.

Making sure milk is free from antibiotic residues
The milk we collect from a treated cow is tipped out until there is no risk of antibiotic residues in the milk. The antibiotics come with quite precise details of how long they remain in meat and milk. It’s critical information because nobody wants food laced with antibiotics, especially those with life-threatening allergies.

As precautionary measures, we:

  • paint the cow’s udder red as a warning to everyone in the dairy that she either needs more treatment or to have her milk disposed of,
  • write her treatment needs and the time her milk needs to be withheld from the vat on a whiteboard in the dairy for all to see, and
  • record all her treatment details in a quality and treatment register.

After she has finished a course of treatment, we check the cow again to be sure the infection has cleared up.

Testing for antibiotic residues
Even with all these protocols, it’s good to know that if milk contaminated with antibiotics somehow got into the vat, there are more safeguards in place. In the next post, a guest from milk processor, Fonterra, will explain how they test our milk for antibiotics.

The bottom line
Our cows live good, healthy lives and rarely fall ill but when they do get sick, we give them the best treatment available straight away. For people and animals alike, antibiotics are our last line of defence against misery and death, so we use them only when really needed and then with great care. And I don’t want to go back to a world without them.

When the lights go out on farm

Jumping off the milk vat

Zoe leaps off the vat ladder to her Papa

Our power has become so unreliable I’ve given up resetting the microwave clock but this is far from the most serious consequence for our dairy farm. Unfortunately, we use a lot of power. There are water pumps, milking machines and, most critically, refrigeration. Our milk is stored in a stainless-steel 17,500-litre vat before it is collected by the tanker.

The vat keeps the milk at a steady 4 degrees Celsius to keep it fresh. As part of the co-op’s quality assurance program, the tanker driver records the temperature upon collection. If the refrigeration fails, we need to organise immediate collection to prevent a quality failure.

The most common cause of problems with the vat are power outages or spikes that mean we have to manually reset the compressors. That’s what happened yesterday and the milk was not kept cool enough. The co-op’s lab will test the milk to make sure it remained fresh. Fingers crossed.

Power outages also affect milking of course. There’s nothing worse than being halfway through milking when the power goes off and looks like staying off for a while. The dilemma is whether to let the cows out and know they won’t be comfortable overnight or keep them waiting in the yard and hope it comes back on quickly.

A little while ago, the electricity infrastructure company rang to do a customer satisfaction survey. I don’t think they were expecting quite the ear-bashing they got!