The first three weeks set the tone
A disproportionate share of new clinical mastitis cases for the entire season happen in the first three weeks of lactation. That isn't a coincidence. It's the moment when the udder is most exposed: high production, teat canals freshly open, cows moving out of springer mobs into the shed, hygiene routines being rebuilt from scratch with new staff and new patterns. Get those three weeks right, and you give yourself a much easier nine months. Get them wrong, and you spend the rest of the season catching up.
Three things make the difference between a season that runs itself and one that fights you the whole way:
- a disciplined first-milking routine,
- continuous visibility on what's happening in the herd, and
- the ability to act on what you see when you see it.
Each one is useful on its own. Together, they compound.
Pillar 1: A disciplined first milking
The first time a cow enters the shed after calving sets the contamination patterns for her entire lactation. The first milking is when teat canals are still partly open, the colostrum environment is rich for bacterial growth, the cow is stressed, and any environmental pathogens that get a foothold now will compound through the weeks that follow.
A clean first milking is more than a hygiene exercise. It's the first measurable input into the season's mastitis trajectory.
The specifics, the order of operations, the kit, the timing, how cows are drafted, how any cow showing signs is handled, are best laid out as a wall reference in the shed where every milker can see them. We've put ours together as a single-page poster, available free to anyone who wants one. We're working with FIL to deliver posters in person where possible, so a conversation about how it fits your shed routine comes with it.
Pillar 2: Continuous visibility
You can't fix what you can't see. The udder health picture on a dairy farm changes constantly through the season: contagious pressure builds and recedes, environmental challenges peak and fade, hygiene routines drift, new staff bring new habits. By the time the bulk tank SCC moves, the underlying change has often been brewing for weeks.
Herd tests are part of the picture. They give you individual cow SCCs and production data, and they have a clear role to play. But they also have limits. SCC is a proxy for inflammation, not a diagnosis: a cow with a low SCC can still carry Staph. aureus, and a cow with a high SCC may be fighting an environmental pathogen that doesn't need treatment. And at around $4 per cow per test all in, four herd tests on a 450-cow herd cost more than $7,000 across a season, meaningful spend for a dataset that tells you who is high but not why.
This is where bulk tank surveillance earns its place. Four bulk tank samples timed through the season give you the pathogen profile and hygiene signals: what's actually circulating, in what intensity, and where the levers are to pull. A surveillance programme at around $325 per test comes in well under the cost of a single conventional herd test on a typical farm, with information that's directly actionable rather than purely descriptive.
For many farms, the better question isn't whether to do more herd tests. It's whether to pair fewer herd tests with continuous bulk tank surveillance that fills in the diagnostic gap.
Pillar 3: On-farm pathogen ID, in real time
When a cow flags, high SCC, RMT reactive, or clinical case, the question isn't whether to act. It's how. Reach for a tube without knowing what's on the plate, and you'll over-treat the cases that would have self-resolved and under-treat the ones that needed something different.
This is where the research is most clear. Lago and colleagues (2011), in a multi-herd clinical trial across eight commercial farms in North America, showed that selective treatment of clinical mastitis based on on-farm culture results halved antibiotic use, with no negative effects on clinical outcomes, recurrence rates, or cow survival. Half. Without giving up any clinical ground.
The principle is simple. A 24-hour on-farm culture turns guesswork into a quarter-level decision. Treat what needs treating with the right product. Don't treat what doesn't need it. Segregate or cull the cows whose pathogen profile says they're a herd-level risk. The decision-making improves at every level: clinical, commercial, and stewardship.
This is also where the broader cost picture comes back into focus. The visible costs of a clinical case, the antibiotics and the discarded milk, are the smallest part of what mastitis actually costs the farm. The much larger costs sit on the other side of the case: premature culling and the replacement heifer, lost future milk production, and lost reproductive performance. In the most widely cited economic model of a clinical case (Rollin and colleagues, 2015), premature culling and replacement alone account for 41% of total cost; future milk production loss accounts for another 28%. Targeted treatment built on diagnostic evidence reduces all of them at the same time.
The regulatory direction, and what it means for you
The dairy industry is moving toward more reasoned antibiotic use. The New Zealand Veterinary Association's aspirational goal, set in 2015, is that by 2030 New Zealand won't need antibiotics for the maintenance of animal health and wellness. That isn't a regulation. It's a direction. And it's the direction the profession, the processors, and the best operators are all walking in.
In practical terms, that means a shift toward Selective Dry Cow Antibiotic Therapy (DCAT), targeted treatment of clinical cases during lactation, and prevention strategies that reduce the pool of infected cows in the first place. Herds with the diagnostic visibility to qualify for selective DCAT and run it well end the season with lower antibiotic use, lower SCC, healthier udders, and a stronger position on every milk quality metric. Herds without that visibility are increasingly the outliers.
The path from one to the other isn't a single decision. It's continuous monitoring, on-farm culture when cases arise, hygiene discipline through the season, and a vet who has good data to work with at every conversation. The diagnostics don't replace clinical judgement. They make it sharper.
Why this matters now
There's a lot of advice in the dairy industry. Some of it is excellent. Some of it is offered without the diagnostic evidence to back it up: recommendations made on intuition or on what worked last season. Advice without diagnostic evidence is just an opinion, and opinions are a poor foundation for spending decisions and animal health outcomes.
The opposite of that is a system where every recommendation, from the vet, from us, from your local partner, sits on top of data that everyone in the conversation can see. That's what continuous monitoring and on-farm pathogen ID make possible. The conversation moves from "I think we should" to "the data shows we should." Better for the cows, better for the farm's bottom line, better for the relationship with your milk processor and your vet.
How it compounds
None of these pillars is a single-season fix. Their value is in the compounding.
- A clean first milking gives you a herd that calves with less infection.
- Continuous monitoring spots emerging issues weeks earlier than waiting for the bulk tank to tell you.
- On-farm pathogen ID means every treatment decision is targeted rather than blanket.
Each one shaves a few percent off the year's mastitis cost and a few hundred from the antibiotic spend. Over three or four seasons, the same farm is unrecognisable.
That's the recipe. Not a single tool, not a magic intervention. Just the discipline to do the right thing at the right time, with the data to know what the right thing is.
References
1. Lago et al., 2011a: on-farm culture halves antibiotic use
Lago, A., Godden, S.M., Bey, R., Ruegg, P.L., Leslie, K. (2011). The selective treatment of clinical mastitis based on on-farm culture results: I. Effects on antibiotic use, milk withholding time, and short-term clinical and bacteriological outcomes. Journal of Dairy Science 94(9), 4441–4456.
Extract: "Selective treatment of clinical mastitis based on on-farm culture results halves antibiotic use and tends to decrease milk withholding time without affecting short-term clinical and bacteriological outcomes."
2. Lago et al., 2011b: long-term outcomes of selective treatment
Lago, A., Godden, S.M., Bey, R., Ruegg, P.L., Leslie, K. (2011). The selective treatment of clinical mastitis based on on-farm culture results: II. Effects on lactation performance, including clinical mastitis recurrence, somatic cell count, milk production, and cow survival. Journal of Dairy Science 94(9), 4457–4467.
Extract: Milk production, linear score somatic cell count, and risk of mastitis recurrence or removal by culling or death were not different between cows assigned to selective on-farm culture-based treatment and those assigned to blanket antibiotic treatment.
3. Rollin et al., 2015: economic model of a clinical mastitis case
Rollin, E., Dhuyvetter, K.C., Overton, M.W. (2015). The cost of clinical mastitis in the first 30 days of lactation: An economic modeling tool. Preventive Veterinary Medicine 122(3), 257–264.
Extract: "The average case of clinical mastitis resulted in a total economic cost of $444. Future milk production loss represents 28% of total cost, and future culling and replacement loss represents 41% of the total cost of a case of clinical mastitis."
Note: This is a US dataset, but the cost structure (heifer replacement cost dominates) applies even more strongly to the NZ market in 2026, where replacement heifer values sit above the figures Rollin used
4. Halasa et al., 2007: review of mastitis economics
Halasa, T., Huijps, K., Østerås, O., Hogeveen, H. (2007). Economic effects of bovine mastitis and mastitis management: a review. Veterinary Quarterly 29(1), 18–31.
Extract: Review of frameworks for calculating mastitis economics. Identifies the major cost categories: production losses, culling and replacement, treatment costs, discarded milk, and labour. Useful background reference, though per-case breakdowns vary by region and year (see Rollin et al. 2015 for current figures).
5. NZVA 2030 aspirational goal: antimicrobial stewardship
New Zealand Veterinary Association. Antimicrobial resistance and antibiotic stewardship. "By 2030 New Zealand Inc. will not need antibiotics for the maintenance of animal health and wellness."
