Heat stress management in dairy cows

Sarah M Kunda

Benine Ackermann

Heat stress occurs when cows generate and absorb more heat than what they can easily get rid of. Heat is mostly generated during the hot periods of the day and during feeding. The major causes of heat stress are high temperatures and humidity. Cows experience heat stress at a much lower temperature than humans, namely around 22 degrees Celsius. Good ventilation, respiration, and sweating are ways in which cows manage heat stress.

Importance of heat stress management

It is important to manage heat stress because heat stress leads to more stress, lowers milk production, and also leads to an increased rate of disease and death. Heat stress leads to production costs and poses a danger to the dairy business; it is therefore very important to manage it and avoid costs and losses due to lower productivity and disease.

Methods of heat stress management

There are many ways to manage heat stress such as using ventilation, providing shade, hydration, and cooling with water sprinklers.

Ventilation

Barn ventilation allows air exchange between the cows and the outside environment via natural or mechanical means. Natural ventilation depends mainly on wind and hot air movement. It involves uncrowded barns and open ridges, sidewalls, or eaves to allow air in and out of the barn. Mechanical means can involve fans or extraction fans.

Shade

Shading is one of the most easily implemented and economical methods to minimise heat from solar radiation. Barns must be constructed strategically to avoid direct and indirect sunlight passing through. Numerous types of shading are available, from trees (which are easily killed by high cow density), to metal (roofs) and synthetic materials (shade cloth).

Hydration

Hydration is important both during heat stress and cold stress. Water intake increases during heat stress. A cow can drink about 50 to 60 gallon (190 to 227 litre) per day. It is therefore very important to provide more locations for cool and clean water.

Cooling with water sprinklers

Water sprinklers will wet the cow’s body and reduce its body temperature. Sprinklers should wet the back of the cow and then stop to allow the water to evaporate prior to another cycle. It is advised to have a water sprinkler at the milking parlour exit too.

Nutritional management

Feeding higher-quality forages increases the energy content of the diet, which helps to maintain adequate rumination, and decreases the fermentation heat associated with feeding lower-quality forages. Starch should be minimised and feed is to be given in the cooler times of the day.

Genetic selection

Another option used to minimise heat stress is to select a breed that can handle the constraints of the environment the animals are reared in. Another alternative is to select for specific traits conferring resistance to heat stress.