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It happens every year.
Summer arrives, temperatures rise, and reproduction is the first thing to suffer.
At surprisingly moderate conditions, around 24°C / 76°F with 50% humidity, reproductive performance can already begin to decline. That means getting cows pregnant from June through October becomes a challenge on many farms.
And when cows don’t get pregnant on time, the consequences show up months later.
No pregnancy means no calf.
No calf means no next lactation.
And no next lactation means no milk.
That’s not opinion — that’s a plain and simple fact.
Reproduction Is Extremely Sensitive to Heat
Maintaining core body temperature is critical to reproductive success.
Once a cow’s body temperature rises, the reproductive system is one of the first systems to shut down. The cow is prioritizing survival, not pregnancy.
When core body temperature exceeds 40°C / 104°F, the consequences for a newly conceived embryo can be catastrophic.
Many producers see summer conception rates fall into the single digits as temperatures rise. Those losses don’t stay in summer — they ripple through the herd for the rest of the year.
What the Research Shows
Research published in the Journal of Dairy Science clearly demonstrates how sensitive conception is to temperature increases:
“The upper critical temperature for heat stress to begin was between 25 and 26°C.
Conception rate declined from 61% to 45% when rectal temperature 12 hours post-breeding increased by just 1°C.
Cows with rectal temperatures of 40°C following exposure to 32.2°C ambient temperatures for 72 hours after insemination had conception rates of 0%, compared to 48% when rectal temperature remained at 38.5°C.”
Read the full article here:https://www.sciencedirect.com/science/article/pii/S0022030203740430
Put simply:
- A 1°C rise in core body temperature can reduce conception by 20% or more
- Sustained heat exposure during the first 72 hours post-breeding can reduce conception to zero
Now imagine what that does to a herd over an entire summer.
Why Cooling Core Body Temperature Matters
You can’t fix reproduction problems in the fall if they were caused by heat stress in the summer.
That’s why investing in a system that:
- Automatically responds to temperature and humidity
- Adjusts itself in real time
- And maintains cow core body temperature
can have such a powerful impact on reproductive performance.
This isn’t about comfort alone — it’s about protecting fertility when it matters most.
What Farmers Are Seeing on Their Farms
A dairy farmer near Kidron, Ohio, shared this after installing the CowKühlerZ series by Core Cool Systems:
“The most significant difference for us was in conception rate. Our reproduction percentage was horrible before. We never used to be able to breed cows in the summer.
Now we’re getting most cows in calf on the first breeding cycle throughout the summer, regardless of heat events. Our AI technician commented last summer that we were the only farm in the entire area successfully getting cows pregnant.”
That’s the difference between fighting heat stress and preventing it.
The Real Cost of Poor Summer Reproduction
Low summer conception rates create:
- Missed breedings
- Delayed calvings
- Extended days open
- Disrupted dry-off schedules
- Fewer cows entering lactation
- Less milk in the tank
- And a management nightmare that follows you all year long.
You shouldn’t have to accept that as “normal.”
The Bottom Line
Preventing heat stress isn’t just about surviving summer.
It’s about:
- Getting cows pregnant on the first attempt
- Calving on schedule
- Keeping cows moving smoothly into the next lactation
- And keeping milk — and revenue — flowing
No calves. No milk. It really is that simple.
If summer heat is costing you pregnancies, it’s already costing you calves — and that means lost milk months down the road.
You can’t make up for missed conceptions later.
You can only prevent them now.
If you want to protect reproduction, calving schedules, and milk flow through the rest of the year, it starts with maintaining core body temperature during heat events and everyday warm conditions.
Now is the perfect time to plan.
Talk with a Core Cool Systems representative about how fully automated, stall-level cooling can help protect reproduction on your farm.
Email nancy@corecoolsystems.com or Visit www.corecoolsystems.com
Because when cows stay core cool, they breed back sooner and stay in calf — and that keeps the milk flowing.