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How do cows cope in a warming climate?

In this article, Dr Marie Dittmann discusses the impact of rising temperatures on dairy cows.
Cow poking it's head through some bars within a farm.
© University of Reading

As briefly discussed in Step 2.6, dairy cows suffer from heat stress when temperatures rise over the level they are adapted to, which generally results in lower productivity and even higher mortality. What problems does the dairy industry face with rising temperatures?

The Holstein Friesian cow was originally bred in a moderate, oceanic climate and is the most popular and efficient breed of dairy cattle. Because of this, they have been exported all over the world where they’re sometimes faced with conditions they’re not bred to cope with.

Dairy cows are mammals, so their metabolism creates heat that results in a normal body temperature of around 38-39C. Their options to cool themselves are limited to evaporative cooling, like panting or sweating, by increasing blood flow in their external skin layers to facilitate heat exchange, or by seeking shade or increased airflow to cool themselves.

In dairy cows, heat stress generally leads to a decrease in food intake which affects the performance of the animal. Feed intake in lactating cows begins to decline at about 25-26C. Further effects of heat stress are a lower milk yield, lower fertility, higher incidental rate of metabolic problems or infectious diseases such as mastitis, a bacterial infection of the udder. Due to their short hair, cows can even suffer from sunburn.

Although there are fewer bulls than cows, heat stress on bulls can be a problem. As in most mammals, the testicles are located in the scrotum, outside of the body cavity, because sperm production in the testicles is reduced at high temperature inside the mammal body. Overheating in bulls due to lack of shade or water could therefore lead to reduced fertility.

Heat stress can also result in an abortion of the embryo during a cow’s pregnancy. It is crucial to offer options to cows to prevent heat stress. A number of ventilation systems are available for cow sheds, which include fans, air conditioning or natural ventilation by opening up certain walls of the building. It is also possible to spray cows with water to facilitate evaporative cooling. Roof insulation, the position of roof windows, and the general provision of shade within the shed and on pastures can provide relief from overheating.

Figure 2: Parthenais. A French beef breed originating from the town of Parthenay. ©Marie Dittmann

During hot periods altering the feeding of the cows should be considered. Feeding at night rather than during the heat of the day can help to lower heat stress. The food composition can also be altered to: reduce the heat that is produced by the fermentation of the food inside the cow, supply minerals lost in sweat, and to increase appetite.

You can read more about how farmers can help to avoid heat stress in their cows on the Farmers Weekly website.

Providing shade is one of the easiest and most effective methods to prevent heat stress in cows. Silvopastural approaches aim at combining grazing land with trees or bits of forests. This means that forest fragments, live fences such as trees or hedges, and free standing trees are included into a grazing system. This provides several benefits, including: higher uptake of carbon by the plants, a double use of the land, soil protection, higher biodiversity and, in the case of our dairy cows, cool shade on sunny days and possibly a more diverse diet.

Figure 3: Cattle on silvopastures in Switzerland. ©Marie Dittmann

According to the World Bank, silvopastural systems have proved to be a win-win situation in Costa Rica and Nicaragua. A high carbon sequestration rate was combined with higher milk yields and a larger number of animals, and higher farm income. In more temperate countries in Central Europe, it is common for pastures to contain a few fruit-bearing trees like apple or cherry, which provide shade and scratch posts for the cows.

In the next Step, you will explore how cows can be adapted to climate change with the aid of breeding.

References and further reading:

© University of Reading
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The Future of Farming: Exploring Climate Smart Agriculture

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