A 96-Cow Dairy Lost 210 Litres of Milk a Day Because Flies and Mosquitoes Would Not Let the Herd Lie Down
Last updated: 7 Sep 2026 | 4 Views |
A true story from a dairy farm in Saraburi, Thailand
A 96-Cow Dairy Lost 210 Litres of Milk a Day Because Flies and Mosquitoes Would Not Let the Herd Lie Down
When insects in the barn stopped the herd from lying down, and the lost rest turned into two hundred lost litres every single day
A 96-cow dairy in Saraburi lost more than 200 litres of milk a day for two consecutive rainy seasons. The owner changed feed, changed the mineral mix, and had the vet run bloods. Nothing shifted. Then he put a camera in the barn overnight and saw something he had never seen in twenty-one years. Here are the real numbers, and how the AIROFOG AT35 thermal fogger brought the yield back.
Sompong, 54, has milked cows for twenty-one years in Muak Lek district, Saraburi. His herd is 96 milking cows, delivering to the cooperative morning and evening. His yield figures were once so stable the cooperative used him as a reference farm. But for the last two years, every rainy season the numbers fell for no reason he could explain.
His records are precise. In the dry season the farm averaged 1,340 litres a day. From June to September it dropped to around 1,130 — 210 litres a day gone, for roughly four months, more than 25,000 litres a year.
He tried everything a dairy farmer thinks of. New concentrate formulation, more minerals, silage quality testing, the vet checking udders and running bloods. Everything came back normal, until he began to assume it was simply seasonal heat and humidity he could not do anything about.
The overnight video that changed everything
Sompong's son, who studied animal science, suggested mounting cameras in the barn and reviewing the footage. He set up three in the loafing area for the group with the steepest yield drop and watched it back the next morning. What they saw silenced them both.
On a night in July, that group of cows spent a combined total of roughly three and a half hours lying down and ruminating across the entire night. A comfortable milking cow should lie and ruminate ten to twelve hours a day. On the video the cows rise repeatedly, throw their heads, swish their tails, kick at their bellies and pace without settling.
Zooming in, they could see insects clustered around the eyes, around the udder, and along the hind legs of nearly every animal. On some, they formed visible bands. His son identified stable flies and mosquitoes coming in from the effluent pond and the manure heap behind the barn.
Sompong says he had walked into that barn every day for twenty-one years. He saw insects every day and assumed they were simply part of farming. It never occurred to him that the thing he had grown used to seeing was taking two hundred litres of milk a day.
Why insects cost that much milk
People outside dairy rarely understand how biting insects can move production that much. The explanation is physiological. A milking cow synthesises milk most efficiently while lying and ruminating, because lying substantially increases blood flow through the udder. A cow that lies less produces less, directly.
Second is energy. A cow throwing her head, swishing, kicking and standing all night spends energy on defence instead of on milk. Across a whole night that adds up to a number you can see in the bulk tank.
Third is stress, which raises cortisol, which suppresses the oxytocin needed for milk let-down. A stressed cow does not milk out fully, and the milk left in the udder is itself a driver of mastitis.
Fourth is intake. A cow harassed at the feed fence spends less time eating and eats less, compounding everything above. Put all four together and 210 litres a day is not remotely an exaggeration.
The costs hidden behind the lost milk
More than 25,000 litres a year, at a cooperative price around 20 baht per litre, is roughly 500,000 baht. That is the clearest number, but Sompong says the real damage runs further.
Mastitis rose sharply in the wet months. Last year he had 14 cows with clinical mastitis, each withheld from the tank during antibiotic treatment with all milk discarded. Medication, veterinary fees and dumped milk came to roughly another 90,000 baht.
Conception rates also fell in the rainy season. Chronically stressed cows show weaker heats and settle less reliably, stretching calving intervals. In a dairy system that means lost milking days across the whole herd the following year.
And there is a cost that is hard to measure but real: milk quality. Stressed cows with subclinical mastitis push somatic cell counts up, which affects grade and therefore price directly.
What he tried that did not work, before he found the answer
First he hung fly paper throughout the barn, hundreds of strips a month. They filled within two days, which proved how many insects there were, but the number in the barn never fell, because flies were breeding faster than paper could catch them.
Second he sprayed insecticide using the pressure washer he used for washing down. That soaked the barn, made the floors slick and put cows at risk of falling, wasted a great deal of chemical, and produced droplets far too coarse to reach insects resting in roof cavities and steelwork.
Third he added fans, which genuinely helped where the air moved because flies struggle to land in a breeze — but only where the air reached, and the electricity bill rose by thousands of baht a month while the underlying problem remained.
The turning point came on a visit to a larger dairy where he watched a worker carrying a thermal fogger around the barn and the manure heap in the evening. That owner told him plainly: deal with the adult insects where they rest, rather than chasing them around the barn.
What it actually costs
Lost milk is lost income, directly
210 litres a day for four months a year is roughly 500,000 baht — revenue the farm should have earned from the same cows, the same feed and the same labour. That hurts more than a rising cost, because it is profit that disappears with nothing received in return.
Udder health and the treatment costs that follow
Cows that do not milk out because of stress carry a much higher mastitis risk. This farm had 14 clinical cases in a single year, costing roughly 90,000 baht in medication, veterinary fees and discarded milk during withdrawal periods.
Reproduction and the whole herd's production cycle
Chronic stress weakens heat expression and lowers conception rates. Stretching the calving interval by even one month per cow, multiplied across nearly a hundred animals, means an enormous number of lost milking days the following year.
The health of the people working the farm
Stable flies and mosquitoes do not only trouble the cattle. Farm staff working hours in the barn face vector-borne disease risk, and flies carry enteric pathogens to people and can contaminate milking equipment.
Why the usual fixes do not work
Hanging fly paper
It catches enough to fill within two days, which proves the scale of the problem, but the barn population never falls, because stable flies breed in manure and damp bedding faster than paper can catch them. It measures the problem rather than solving it.
Spraying with a pressure washer
This soaks the barn and makes floors slick, which is dangerous — a cow that slips and injures a hip may have to be culled. It also wastes chemical, because coarse droplets fall immediately and never reach the roof cavities, steelwork and dark corners where insects rest by day.
Adding more fans
Genuinely useful within the airflow, and helpful for heat stress too, but it removes no insects from the farm, and several thousand baht a month in extra electricity is a permanent cost that never addresses the source.
Spreading lime or deodoriser on the manure heap
It helps with odour and reduces egg laying somewhat, but it does nothing about the tens of thousands of adult insects already present, and it does not cover the other breeding sites: the effluent pond, the wash-down channels and spilled silage.
Pour-ons and ear tags on the animals
These protect only the individual animal and only for a limited period, and the per-head cost is significant across nearly a hundred cows. Most importantly, when the environmental population stays the same, the pressure on the herd stays the same.
You have to reduce the adult insect population in the farm environment, not just protect individual animals
After that farm visit, Sompong understood the principle he had missed for years. Stable flies and mosquitoes spend most of the day resting in dark, still places — under the barn roof, in steelwork, in post recesses, on rear walls, in the shrubbery around the farm, on the manure heap and around the effluent pond — and only then move out to work on the cattle.
Chasing insects around the barn is therefore treating the endpoint. What actually works is reducing the adult population in those resting places, which requires equipment that carries the product up into cavities and heights rather than coarse droplets that fall to the floor.
A thermal fogger does this best. The fog rises under the roof, penetrates the steelwork, and blankets the manure heap and perimeter vegetation in a matter of minutes — without wetting the barn or making the floor slippery.
The machine also has to survive humidity, ammonia and frequent washing down. That is why Sompong chose the AIROFOG AT35, with a body built from 100 percent stainless steel.
10 reasons the AIROFOG AT35 thermal fogger solves it
1. Fog rises into roof spaces and steelwork where insects rest
Stable flies rest overnight under roofing, on steel beams and in post recesses — places a pressure washer never reaches. The AIROFOG AT35 produces a fog light enough to rise and blanket those areas, treating insects where they actually are rather than the air the cows stand in.
2. It does not wet the barn or make floors slippery
This matters enormously on a dairy, because one cow slipping can mean culling her. Thermal fog uses a tiny fraction of the liquid volume of water spraying, so the floor stays dry and safe while the insect control is far more effective.
3. A 100 percent stainless steel body that resists ammonia and barn humidity
Dairy barn air carries high ammonia and constant humidity, which corrodes ordinary metals quickly. A fully stainless body lasts far longer in those conditions, which is why its annual cost beats a cheap machine replaced every year or two.
4. Carried on the shoulder across the whole farm — barn, manure heap and ponds
Insect sources on a dairy are spread across places no vehicle can reach: behind the barn, the manure heap, the effluent pond and the boundary vegetation. The AT35 is light enough for one person to walk the entire circuit in a single pass without moving heavy equipment.
5. Runs both water-based and oil-based formulations
Dairy farms must choose chemistry carefully because of feed and milk. Accepting both formulation types means you can use products registered for livestock exactly as your veterinarian advises, and rotate products to slow resistance.
6. Fog on your own schedule, fitted to the milking routine
Dairy farms run on a rigid timetable. Owning the machine means fogging while the herd is out at pasture or after the evening milking — the safest and most effective windows — rather than waiting on a contractor who arrives when it suits him.
7. Covers the whole farm in well under an hour
A 96-cow barn plus manure heap and effluent pond takes roughly 30 to 45 minutes per pass with the AT35. That is short enough to become a genuine daily routine without disrupting anything else on the farm.
8. Certified to German and British standards
These certifications mean the machine has been tested for safety and droplet-size consistency, which matters greatly on a livestock farm because consistent droplets mean precise chemical dosing and predictable results.
9. Compliant with Thai government standard equipment specifications
For government-run farms, livestock research and development centres, dairy cooperatives and university demonstration farms, meeting the official standard equipment schedule makes procurement and acceptance inspection straightforward.
10. A Thai service centre with genuine parts and 10-plus years of technician experience
A dairy cannot pause for a single day. If a machine fails and parts take a month from overseas, the insect population rebuilds and yield falls again. Domestic service and genuine parts are worth more than any discount at purchase.
Before the thermal fogger
- Yield falling from 1,340 to 1,130 litres a day through the rainy season
- Cows lying and ruminating only about three and a half hours per night
- 14 clinical mastitis cases in one year
- Roughly 90,000 baht a year in medication and discarded milk
- Thousands of baht a month on fly paper and extra fan electricity
- Noticeably lower conception rates through the wet months
After the thermal fogger
- Rainy-season yield back to an average of 1,295 litres a day within six weeks
- Lying and ruminating time up to roughly eight and a half hours per night
- Mastitis down to 4 cases the following year
- Somatic cell counts down enough to lift the milk grade
- Fly paper almost entirely discontinued
- Fogging running cost in the tens to low hundreds of baht per day
The three-step process
1. Survey and map resting sites and breeding sources
Walk the farm in daylight to find where insects rest — under the roof, in steelwork, post recesses, rear walls — and separately walk the breeding sources: the manure heap, effluent pond, wash-down channels, spilled silage and any container holding water. Separate what can be fixed immediately from what needs regular treatment.
2. Fog on a schedule that fits the milking routine
The best windows are after the evening milking and while the herd is out at pasture. Treat under the roof, the steelwork, the walls, the manure heap and the boundary vegetation. Fog daily for the first two weeks to break the cycle, then two to three times a week in the rainy season and weekly in the dry.
3. Measure with yield figures and cow behaviour
The best indicators on a dairy are daily milk volume and lying-and-ruminating time, which you can read from a camera or by observing at the same hour each night. Log both alongside catch counts on a few reference fly papers. Those three numbers tell you clearly whether to raise or lower fogging frequency.
From someone who uses one
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The breeding sites dairy farmers most often miss
The manure heap is the largest stable fly nursery on every dairy. Flies lay in manure at the right moisture, and in Thai heat and humidity the cycle from egg to adult takes only about seven to ten days. What works is turning the heap so it heats and destroys eggs and larvae, or removing it more frequently through the wet season, alongside fogging the surface.
The effluent pond from barn wash-down is a major mosquito source, especially where weeds grow along the edge, because mosquitoes prefer still water with cover. Trimming the vegetation around the edge and stocking larvivorous fish is an extremely low-cost measure with a clear effect.
Wash-down channels with insufficient fall hold pools along their length — the most-overlooked source of all, because the channel appears to be running. Correcting the fall or scraping out sediment regularly fixes it permanently.
Last is spilled silage and concentrate around the feed fence, which combines with moisture to become a small fly nursery within days. Sweeping the fence line daily is a small job with a large return.
Chemical safety for milk and animals on the farm
The concern dairy farmers raise first is contamination of milk. The answer is that with products registered for livestock premises used strictly per label, the risk is very low — but it has to be done properly, not by habit.
The most important rule is never to fog with cattle in the building. Fog while the herd is at pasture or moved to another pen, then allow at least 30 to 60 minutes with ventilation open before bringing them back.
Cover feed troughs, water tanks and all milking equipment before every application. Anything that contacts milk directly should be cleaned to the usual standard before the next milking. This is not a step to shortcut.
Finally, consult your farm veterinarian or district livestock officer on product choice and dilution, particularly if you supply a cooperative that samples for residues. Keeping a written log of chemical use is strongly in the farm's favour under any inspection.
Frequently asked questions
Can I fog while the cows are in the barn?
No. Fog while the herd is out at pasture or moved to another pen, then allow roughly 30 to 60 minutes with ventilation before bringing them back. In practice this is easy, because dairy farms already run on a fixed timetable.
Will chemical residues end up in the milk?
With products registered for livestock premises, used at label rates, and with milking equipment and feed troughs covered every time, the risk is very low. Consult your farm veterinarian on product choice and keep a record of every application.
How many machines does a farm of my size need?
A dairy of 50 to 150 cows is generally fine with one machine, since the barn, manure heap and pond can be covered in 30 to 45 minutes. Larger farms, or farms with several separated barns, should have two so the whole circuit fits in one window.
How often should I fog?
Daily for the first two weeks to break the breeding cycle, then two to three times a week through the rainy season and once a week in the dry season. Let daily milk volume and fly-paper counts drive the decision, not the calendar.
Does fogging make the barn floor slippery?
No, and this is the key advantage over water spraying. Thermal fog uses a very small liquid volume, so the floor stays dry and safe for the cows — which matters greatly, since one bad fall can end an animal's productive life.
Does it handle both flies and mosquitoes?
Yes. Thermal fog controls flying adult insects including stable flies and mosquitoes, the two main problems on a dairy. But it must be paired with breeding-source management — manure and standing water — or new generations simply replace what you removed.
How many weeks before milk yield responds?
Most farms see behaviour change within one to two weeks: cows lying and ruminating longer and settling more. Yield figures usually move clearly in weeks four to six, because the animals need time to recover from accumulated stress.
If the machine breaks down, how long is the wait?
AIROFOG maintains a service centre and genuine parts in Thailand with technicians of more than 10 years' experience, so there is no month-long overseas wait. On a farm where stopping means yield falling again, repair speed is worth more than the purchase price.
The cows cannot tell you — but the bulk tank does, every day
The clearest lesson in Sompong's story is that the problems we see every day until we stop noticing them are usually the problems we never count — and what is never counted is never fixed.
A cow has no way to tell you she could not lie down. The tank tells you every single day. Farms that record daily yield and genuinely observe cow behaviour catch these signals long before they compound into hundreds of thousands of baht.
Insect control on a dairy is not a side task. It belongs alongside feed and water as part of managing production, and it is among the fastest-paying investments a dairy farm can make.
Talk to the World Health Disinfection team about the right machine and a fogging schedule matched to your herd size and milking routine.
See the machine and pricing — click here
Call 065-556-6294 or add LINE @whd268
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Related keywords: thermal fogger, dairy farm fly control, livestock mosquito control, AIROFOG AT35, milk yield, barn fogging machine
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