Saturday, December 9, 2023

Targeted antibiotic use in dairy cows offers wide range of benefits

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A ban on blanket-use dry cow therapy in the Netherlands has seen a wide range of benefits as New Zealand works towards reducing antibiotic use.
There is a growing expectation that antibiotic dry cow therapy will only be used selectively to treat existing intramammary infections.
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Every year at dry-off more and more farmers are opting to use selective antibiotic dry cow therapy and there is a big push to reduce the numbers of cows receiving DCT for several reasons. The big ticket is antibiotic resistance.

Overuse of antibiotics can lead to the emergence of antibiotic-resistant bacteria, making it harder to treat infections in both animals and humans. 

In 2012 the Netherlands government placed a ban on preventative use of antibiotics, which meant blanket DCT could no longer be used and farmers were given parameters around DCT use. The decision to switch to selective DCT was driven in part by consumer demand for less antibiotic use in food and to lessen the risk of antibiotic resistance.

Since the ban, the country’s antibiotic use in dairy has dropped 63%, which was the aim of the government regulation. The Dutch have also seen fewer health issues presenting to hospitals linked to antibiotic-resistant bacteria because, as the use of antibiotics decreased, there was less pressure on bacteria to develop resistance. 

Over the three-year period after the ban, there was a 50% reduction in use of dry cow antibiotics and there was a 25% drop in clinical mastitis cases over the same time frame. The bulk milk somatic cell count (SCC) was above 200,000 cell/mL at the time of the ban and by 2018 it had reduced to about 170,000.

With restrictions on antibiotic usage, farmers were better able to target cows that need antibiotic treatment for udder infections, which led to better treatment outcomes and improved overall cow health.

These examples from the Netherlands offer an excellent case study of a country that has worked through the implementation pains of transitioning to a selective DCT protocol. Seeing the financial, cow health, milk quality and sustainability benefits as well as a reduction in antibiotic resistance has highlighted the value of reducing DCT use.

Here in New Zealand there is heightened expectation that antibiotic DCT will only be used to treat existing intramammary infections. This means that, before deciding if a cow is eligible for DCT, there will need to be evidence of an intramammary infection.

The usual “gold standard” for indicating the presence of bacteria is bacterial culture, carried out in a laboratory. In countries such as Denmark, Finland, Norway and Sweden, evidence of bacterial infection based on culture or DNA analysis is required before DCT is prescribed. The practicalities of bacterial culture under the seasonal system in NZ is difficult but there are other acceptable methods such as SCC and supporting farm information.

For herds with a low bulk milk SCC, a low incidence rate of clinical mastitis and low culling percentage for mastitis-related problems, it is unlikely there are many cows truly infected at drying-off. For these herds, routine use of antibiotics in every quarter of every cow at the end of lactation is not justified and veterinarians will be reluctant to prescribe DCT for large numbers of the herd.

The most appropriate strategy must be planned with a veterinarian and the industry-agreed recommendation in DairyNZ’s SmartSAMM is to ensure that all cows are protected by some form of treatment during the dry period. In most herds it is appropriate to use a targeted or selective approach, so that cows considered “at risk” of being infected are treated with antibiotic DCT, and all cows receive an internal teat sealant.

The goal posed by the New Zealand Veterinary Association is that by 2030, NZ Inc will not need antibiotics for the maintenance of the health and welfare of animals. This doesn’t mean we cannot use antibiotics, it just means we need to use them wisely and when they are actually required.

Antimicrobial use for treatment and control of mastitis is the major indicator for antibiotic use in NZ dairy cows. The use of selective DCT based on infection status is encouraged to reduce the use of antibiotics and minimise the development of antibiotic resistance. Sort your plan with your veterinarian for drying-off as well as ways to minimise antibiotic use and mastitis levels throughout the season. Monitor your progress and benchmark against others using WelFarm with your vet team.

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