BVD Control Begins Long Before You See A Problem
Bovine Viral Diarrhoea (BVD) is sometimes viewed as a dairy industry issue, but the reality is that the disease can have serious consequences for beef breeding herds as well.
From 1 January 2027, that approach could become much harder to justify.
Updated Veterinary Council guidance will put greater emphasis on antimicrobial DCT being justified at the individualcow level, strengthening the expectation that antibiotics are used only where there is evidence they are needed.
MSD Animal Health veterinary technical advisor Matt Buckley says selective DCT itself isn’t new. What is changing is the weight behind it and emerging technologies to support smarter dry cow decisions.
“The thresholds and guidelines have been there for quite a while. The difference now is that vets have much stronger backing to say, ‘show me the evidence that this cow needs antibiotic dry cow therapy.’”
And recent New Zealand research suggests that for the vast majority of herds, treating every cow isn’t necessary.
DairyNZ says extensive analysis has found blanket DCT provides a benefit only in herds where bulk milk somatic cell count (BMSCC) is above 250,000 cells/mL and rises by more than 50,000 cells/ mL during the final three months of the season.
Fewer than 5% of New Zealand herds are likely to meet those criteria.
For the rest, DairyNZ’s advice is selective antibiotic DCT for qualifying cows, combined with internal teat sealant for all cows to help prevent new infections during the dry period.
Why does it matter?
The objective isn’t to remove access to antibiotics for cows that need them, but to avoid using them where there isn’t evidence they’re required, reducing unnecessary antimicrobial use without compromising animal health.
It also forms part of the much bigger challenge facing agriculture and human health: antimicrobial resistance.
Buckley says protecting the effectiveness of the antibiotics available to treat both people and animals is ultimately what responsible use is about.
“We want antibiotics to work when we genuinely need them. This isn’t about not treating cows that need treatment – it’s about the right treatment, for the right cow, at the right time.”
For New Zealand dairy, that’s also an important position to protect. DairyNZ says New Zealand farmers already rank among the lowest users of antibiotics internationally.
Selective DCT might sound straightforward in principle, but the harder question is how to make it work in the shed.
Unlike a blanket approach, selective DCT requires farmers and vets to determine which individual cows warrant antibiotic treatment, using evidence such as clinical mastitis records and individual-cow somatic cell count (SCC) information.
Buckley says this is where the conversation needs to move beyond simply telling farmers to use fewer antibiotics.
“If we’re asking a farmer to make a decision for every individual cow, we need to make that practical,” he says.
Building a picture of the cow over time
Traditionally, individual-cow SCC information has commonly come from herd testing. Increasingly, in-line milk monitoring can provide another source of that information.
A 2024 study published in the Journal of Dairy Science involving 1544 cows across four predominantly pasture-fed New Zealand dairy herds investigated whether SenseHub Dairy In-Line Somatic Cell Count could help identify cows for different treatments at dry-off.
Researchers found that in-line SCC information collected over the final 12 weeks of lactation delivered similar results to conventional herdtest SCC measures in identifying cows with major intramammary infections at dry-off.
The researchers concluded that the in-line SCC data had utility for selecting cows for either antimicrobial DCT or internal teat sealant at the end of lactation.
For Buckley, the value of collecting that information extends well beyond the dryoff decision. Having individual-cow SCC data available throughout the season gives farmers a deeper picture of what’s happening within their herd, including the ability to identify cows with rising SCC earlier and investigate potential mastitis issues sooner, ultimately driving better outcomes and more milk the vat.
“It’s about having more information about the individual cow and being able to act on it,” says Buckley. “By the time you get to dry-off, you’ve already built up that history rather than starting from scratch.”
Turning Data Into A Decision
Many farmers already use herd-test results, clinical mastitis records, dry-off dates and other information to create reports identifying cows that meet the criteria for antibiotic DCT.
“If you’ve got a report that can identify the cows that are above the agreed threshold over the last 12 weeks and have had mastitis, you’ve got your list of cows that need antibiotic Dry Cow Therapy and your list of cows that don’t,” says MSD animal health veterinary technical Advisor Matt Buckley.
“It becomes a two-second job.”
Technology can also help make those decisions easier to implement on farm, including by helping farmers identify and separate cows requiring different treatments.
Milk volume can also help determine when an individual cow is ready to be dried off, while other individual-cow data can help farmers manage the wider transition through dry-off.
The technology doesn’t replace the veterinarian. The appropriate thresholds and treatment strategy still need to be determined between the farmer and their vet, taking into account the mastitis situation within the individual herd.
“As 2027 approaches, farmers who have traditionally used blanket DCT should talk to their veterinarian about how they will approach dry-off, what criteria will be used to identify cows requiring antibiotic treatment, and whether they have the individual-cow information needed to support those decisions,” says Buckley.
Selective DCT has been best practice for years, and from 2027, farmers and vets will need to work together with evidence regarding which cows actually need antibiotic treatment to ensure that selective DCT decisions are implemented on all farms.
