When summer turns up the heat, it’s time to turn up the cool for cows to protect milk production and animal health.
“Nedap’s heat stress feature within its NedapNow cloud platform can help dairies stay on top of temperature fluctuations, cooling cows faster to avoid the production dips and other challenges that accompany these events,” says Steve Pavelski, Nedap large herd specialist.
A recent analysis shows cows lose up to 8.2% of a day’s milk over the week following a day of heat stress. This loss ranges from 1.6 – 2.2% following a day of low stress, 3.2% following a day of moderate stress and 8.2% following a day of extreme stress.1
Extrapolating these results over time, on average, herds examined in the research lost 1% of annual yield each year due to heat stress, though the exact loss varied year over year. For example, losses were higher during a particularly warm summer. Over the five-year period studied, sample herds lost $245 million in revenue.1 These losses have an obvious impact on a dairy’s bottom line, particularly when margins are thin.
Thanks to accurate, real-time data, like that available via SmartTag ear tags, farms like Milking R Dairy in Okeechobee, Florida, are better able to deal with this perennial challenge.
“Our goal with the Nedap tag system is to address issues before they become a bigger problem. We want to keep cows in our herd as long as we can. Longevity pays, reproduction pays and everything ties together to be a profitable farm,” says Garrett Rucks, Milking R Dairy. Addressing heat stress goes a long way toward reaching these goals.
Heat stress defined
The temperature-humidity index (THI) shown below is a commonly used indicator of when heat stress occurs. The index is based on a combination of air temperature and relative humidity.
In cows, a mild form of heat stress occurs above a THI value of 68. As heat stress rises, animals show signs such as an increased respiratory rate, reduced appetite, lower activity and lower milk production and reproductive success.
Figure 1: Temperature-Humidity Index
Effect on health and milk production
Mitigating heat stress isn’t just about maintaining milk yield. There are broader, long-term effects—especially on developing calves. Research shows that calves born to dry cows exposed to heat stress in late pregnancy weigh 1.1 to 12.5 pounds less at birth than those whose dams remained cool.2
These lighter calves also consume less feed and water after birth, resulting in slower growth and development. Over time, the impact continues: their milk production in the first three lactations is consistently lower compared to those from non-stressed cows.
Timely intervention
Nedap’s heat stress feature within its NedapNow cloud platform can help. It detects four levels of heat stress to help dairies appropriately deal with temperature swings:
- No heat stress
- Mild heat stress
- Severe heat stress
- Very severe heat stress
Updated every 15 minutes, the system displays the current stress level and how long it’s persisted—at the pen or group level. This empowers dairy producers to act quickly with measures like turning on fans or activating sprinkler systems.
A validation study on test farms showed that these heat abatement steps can reduce stress levels by at least one full level, directly supporting cow comfort and productivity.
“Use this tool to optimize barn conditions, safeguard herd health and avoid costly productivity losses—all while navigating the hotter months with greater control and confidence,” concludes Pavelski.
Visit nedap.com/now to learn more.
[1] Skidmore M, Hutchins J. 2025. Extreme Heat Leads to Yield Losses for Midwestern Dairy Producers. University of Illinois. Available at: https://farmdocdaily.illinois.edu/2025/03/extreme-heat-leads-to-yield-losses-for-midwestern-dairy-producers.html
[2] Laporta, J, et al. 2020. Late-gestation heat stress impairs daughter and granddaughter lifetime performance. J Dairy Sci., Available at: https://www.journalofdairyscience.org/article/S0022-0302(20)30448-3/fulltext.
