Heat Stress in Dairy Cattle: The Importance of Clean Drinking Water

During warm periods, the risk of heat stress in dairy cattle increases significantly. As early as 20 °C, combined with higher humidity, the first signs of heat stress can occur. This affects the animals’ behaviour, metabolism, and feed intake. An essential factor in limiting these effects is the availability of sufficient and hygienic drinking water.

Significantly Increased Water Demand in Hot Weather

During periods of heat stress, the water demand of dairy cows rises sharply. According to GD Animal Health, this demand can increase by up to 50% compared to normal conditions. Lactating cows may drink more than 150 litres of water per day in hot weather. This is necessary to compensate for the extra evaporation through breathing and sweating, and to keep the body cool (GD Animal Health, 2021; Melkveebedrijf.nl).
To support this need, it is important that the water is not only available in sufficient quantities but also of good microbiological quality.

Microbiological Water Quality is Crucial

Although tap water in the Netherlands generally meets chemical standards, this does not rule out microbiological contamination in piping systems or drinking troughs. Our microbiologist Eva Dankers explains that even water with moderate microbiological quality at the source can have major consequences. Biofilm can start forming in the pipes, and bacteria can quickly multiply in drinking troughs. This can lead to very high numbers of microorganisms in the drinking water. It is therefore important to not only check the source of the water but also regularly take samples from the drinking troughs to know what the cows are actually drinking.

During warm periods, the risk of microbiological contamination is even higher, as bacteria grow better and faster at higher temperatures. Most pathogenic bacteria are mesophilic, meaning they thrive optimally between 20 °C and 45 °C. As the temperature rises, bacteria can therefore develop more rapidly in, for example, pipes or troughs, with adverse effects on animal health. It is therefore advised to maintain the drinking water supply at a high standard during hot days.

Ensure fresh and clean drinking water, even during grazing.

Support with the Watter System
 

The Watter system offers farmers a solution to sustainably support the microbiological quality of drinking water. Using electrochemically activated disinfection, the water is continuously cleaned. This reduces both the build-up of biofilm and the presence of unwanted microorganisms in pipes and troughs.

The system is suitable for both barn and pasture applications and works without harmful residues or manual addition of other chemicals. Clean drinking water is also of great importance during grazing, for example when using IBC tanks or surface water such as ditch water, whose quality can vary greatly. This system can help ensure the availability of good and clean drinking water, especially on hot days when water demand is highest.

Recommendations for Farmers

To effectively reduce heat stress in dairy cattle, it is advised to:

• Provide enough drinking points with good flow (minimum 10 cm drinking edge per cow)
• Regularly check smell, colour, temperature, and flow
• Clean drinking troughs several times a day during hot weather
• Consider using disinfection systems to structurally support the microbiological quality of the water

A good approach to water quality helps dairy farmers keep their herds in optimal condition even during warm periods.

Sources

Melkveebedrijf.nl. (2025, 8 July). How to prevent heat stress during the summer months. https://www.melkveebedrijf.nl/diergezondheid/hittestress-melkvee/zo-voorkom-je-hittestress-in-de-zomerse-periodes/

Gd. (n.d.). Prevent heat stress. https://www.gddiergezondheid.nl/diergezondheid/management/hittestress-rundvee?sc_database=web