Cows are herd animals and are originally from colder climate zones. That is why cows feel most comfortable at temperatures between 7°C and 17°C. High temperatures during the summer months can be very difficult for the animals to deal with.
In the following article we take a look at the questions, how you can detect heat stress in your animals and what effects high temperatures have on cows. Additionally, we talk about how smaXtec can help you to intervene at an early stage.
Cows are generally relatively resistant to cold, but they are not resistant to heat. On summer days with outside temperatures of 30°C and over and a relative humidity between 35% and 50%, inner body temperature as well as surface temperature often increases massively. 
Frequent symptoms and consequences of heat stress
If cows are suffering from heat stress the following symptoms often occur:
- increased body temperature
- increased breathing frequency (>80/min); puffing and panting are visible
- head and neck are stretched
- animals increasingly stand close to windows, doors or other better ventilated areas; cows crowd around watering places
- animals are rather inactive and stand around a lot; they spend less time than normal laying down
- reduced feed intake (at temperatures around 26°C approx. 5% less, at 35°C and higher up to 20% less)  
The hypothermic burden is difficult for the animals to deal with. Heat stress has a massive impact on both productivity and health of cows. It can have serious consequences:
- the reduction in feed intake increases the risk of ketosis in high-performance animals
- lack of water intake as cows do not drink enough although sufficient water is available
- milk urea content rises
- milk yield decreases
- milk fat content decreases
- the cell count in the milk increases as concentrated feed is eaten in large amounts and insufficient basic feed is eaten
- fertility suffers – cows show less signs of coming into heat and pregnancy rates drop; increase in the rejection rate
- in the case of persistent heat, the risk of mastitis, laminitis and ruminal acidosis increases
- emigration of pathogenic germs from the digestive tract (E. coli)
If cows have to deal with very severe heat stress, it can lead to much more serious problems and even to death. 
How is heat stress measured?
Heat stress can be measured using the temperature humidity index (THI). The THI is calculated with a formula that is composed of air temperature and relative humidity:
THI = (absolute temperature °C) + (0.36 * temperature of dew point °C) + 41.2
The result can be interpreted to detect possible heat stress.
- THI ≥ 72: early stage of heat stress
- THI ≥ 78: significant heat load
- THI ≥ 82: severe heat stress 
smaXtec and heat stress
Of course, preventative measures against heat stress can be taken without technological assistance. However, these involve additional work as well as cost, e.g. for electricity. By continuously observing heat stress conditions, you can optimise the usage of heat stress revealing measures and thus save money, all whilst ensuring that you keep heat stress to a minimum for your cows to protect their health and safeguard your outcomes.
The smaXtec system comprises of two components enabling the precise detection of heat stress conditions: smaXtec Climate Sensors for measurement of outside factors favouring heat stress and smaXtec Boluses measuring the effects of outside conditions inside the cow. Heat stress can only be monitored reliably if you monitor outside as well as inside temperature. This way, measures to relieve cows’ heat stress can be taken exactly at the right time, saving cost and ensuring constant milk production and cow health.
The Climate Sensor automatically calculates the THI for you and transfers it to the smaXtec Software, where it is displayed in a diagram. If the THI is increased, you will receive a notification and can immediately take measures to improve the climate in the barn.
In combination with the data collected by the smaXtec Boluses, e.g. body temperature, it is possible to draw reliable conclusions about heat stress.
Here you can see examples of how smaXtec displays heat stress:
Example 1: THI measured by Climate Sensor
In this example you see the information provided by the smaXtec Climate Sensor in case of heat stress. It continuously measures humidity and outside temperature. Based on these data, we calculate the THI which is commonly used to assess heat stress. As soon as the smaXtec Climate Sensor detects a risk of heat stress, you will receive an alert. See in the example above how it works.
You can clearly see how the conditions change throughout the day and that the heat stress risk was particularly high in the afternoon.
Additionally, you see the different heat stress alerts provided by the system. The farmer was informed about early indications of heat stress at approximately 9 a.m. and received a further alert about the increasing heat stress level at noon. At 2 p.m., he received a third alert indicating that there is a risk of serious heat stress.
While information on outside conditions are helpful to take relieving measures, only insights from inside allow for conclusions to be drawn on the actual heat stress of cows. You will see its impact in the following example.
Example 2: Temperature alerts
This example curve shows the effects of heat stress on the cow's inner body temperature. During this hot period of three days, increased temperature alerts were sent once daily. You can also see that the alerts were always sent in the evening, e.g. on 25th June at 7:52 p.m. This shows how the long-term exposition to heat stress conditions influences the organism of the cow.
Temperature normalises again during night, but during this hot period the cow suffers again from heat stress the following days.
Heat stress is not only a burden for the organism, but also leads to changes in feed intake and thus affects rumen pH as well.
Example 3: Influence on rumen pH
Heat also impacts cows' eating behaviour: Feed intake decreases up to 25%, leading to reduced productivity. It also leads to a greater risk of rumen acidosis because of:
- Less buffer in the rumen through salivating (panting) and less rumination
- Supply of feed with higher energy density to compensate the reduced feed intake during heat
In the example above, you see the changes in rumen pH caused by heat stress. On that day (26 July) an alert indicating serious heat stress was sent at 2:15 p.m.
Clear changes of rumen pH can be observed: The curve is less stable than usual; fluctuations are very high. This led to a reduced feed efficiency alert. Additionally, the cow showed increased temperature. Another typical alert for a cow being in severe heat stress is increased risk of acidosis.
Summing up, smaXtec supports you with different tools when managing heat stress: The combination of inner body temperature and outside conditions ensures you know when heat stress is getting severe and at what time you need to act. Rumen pH value measurement gives further information on the cows' reaction regarding feed intake and helps you to adapt feeding management to cows’ needs during hot periods.