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How to Reduce the Impact of Heat Stress on Dairy Cows

Excess heat and humidity plays a huge role in the metabolism of the dairy cow, therefore extra care is needed in the summer months in order to limit the impact that heat stress can have during this time. The phenomenon of heat stress results from the combination of high temperatures and humidity, which can vary significantly from country to country. Below is a number of provisions that can be put in place to counteract the negative impact heat stress has on your dairy cattle.

Why do cows have difficulty tolerating high temperatures?

The normal body temperature of a cow averages at 38.5 ° Celsius. While her rumen temperature hovers around 40 ° Celsius due to the heat produced by rumen fermentations, the dairy cow’s comfort zone ranges from 5 to 25 ° Celsius. She is usually better shielded against cold weather rather than hot weather. Therefore, the pending summer season and rising temperatures have consequences on dairy cattle’s behaviour, health, reproduction and production.

The metabolic activity of a cow’s rumen makes her particularly susceptible to heat stress. A cow subject to this condition finds herself suffering from the combination of high temperatures and humidity; this status is measured via the ITH (Index Temperature Humidity). The higher the temperatures and humidity, the stronger the impact of heat stress is.

As outside temperatures rise, cows must release excessive heat through different mechanisms, including breathing and perspiration.
mechanical fan dairy cow heat stress

However, cows reared in two different countries living in similar climatic conditions do not necessarily react at the same level to heat stress. Other than outside temperatures, humidity also plays a major role in the way these animals experience heat stress. The ITH impact worsens as temperatures and the level of relative humidity increase. For example, cows reared in the city of Torreon in Mexico (where temperatures are usually high) are less prone to heat stress than they are in Tunis in Tunisia, which is three degrees less but where there is a higher level of humidity in the atmosphere.

ITH heat stress dairy cow


ITH heat stress dairy cow

What is the impact of heat stress on dairy cows’ activity?

Heat stress can be detected through different signs. Cows affected by this condition usually change their behaviour. They start breathing at a much quicker pace. We can then observe a sharp decline in rumination and milk production. Meanwhile, their maintenance needs increase. As their immune defences are disrupted by the occurrence of oxidative stress, cows become more vulnerable to environmental pressures.
The extent of their ailments can be measured through different parameters:

  • sharp drops in milk production by 10 to 20%;
  • rising occurrences of mastitis, increases in acidosis expenses and veterinary costs;
  • lower conception rates.

Overall, the resulting losses can reach up to € 420 per dairy cow.


How to limit the impact of extreme heat on cows’ productivity

When considering the nutritional aspect, it is advised to increase the energy density of their diet. One should also use a more digestible source of energy in order to limit the impact of ruminal fermentations. Protein degradability should be reduced to promote intestinal absorption.

Increasing the diet distribution, keeping the forage fresh and appetizing is also recommended in order to promote the cow’s consumption.

In addition, our experts advise that rations be given in the evening to encourage cows to ingest their diet at night (when the temperature is cooler).

One should also ensure that the cattle be adequately supplied with water. In this respect, the water flow must be sufficient (15 to 20 l / min) and the number of water points must be adjusted to the number of animals reared on the farm (1 water point / 10 dairy cows).
In areas or countries regularly exposed to this risk, the installation of mechanical fans and sprinklers are recommended to improve air conditions in the barn.

trough summer heat heat stress

Many other elements such as bedding, ventilation, building and breeding management should also be considered in order to reduce the impact of heat stress on the animals’ metabolism. Our experts are help you to achieve this goal, please do not hesitate to contact them!

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