How much water does a cow need during heat stress?

In hot weather, a dairy cow can need up to 150 litres of water per day — did you know that?

During heat stress, a cow needs on average 20 to 50% more water than under normal conditions. At temperatures above 25 degrees Celsius, the daily water requirement of a dairy cow can rise to 150 liters or more, depending on production level and the severity of the heat. In this article, we answer the most frequently asked questions about water consumption, heat stress, and how to best support your livestock during hot periods.

How much extra water does a cow drink at high temperatures?

At high temperatures, a dairy cow’s water intake increases significantly. Under normal conditions, a productive dairy cow drinks an average of 80 to 120 liters per day. Once temperatures exceed 25 degrees Celsius, this can rise to 150 liters or more per day. In extreme heat combined with high humidity, water requirements can even double compared to cooler days.

The reason is straightforward: cows cool themselves primarily through evaporation. They sweat and breathe faster, causing them to lose considerably more moisture. This fluid must be replenished to keep body temperature stable and allow all physiological processes to function normally.

As a rule of thumb: for every liter of milk a cow produces, she needs four to five liters of drinking water. In heat, that ratio increases even further. A high-producing cow yielding 40 liters of milk per day can therefore easily require 160 to 200 liters of water per day in summer.

What are the consequences of insufficient water intake during heat?

Insufficient water intake during heat stress quickly leads to dehydration and has immediate negative effects on the health and production of dairy cattle. Serious health problems can occur with a fluid deficit of as little as 8 to 10 percent of body weight. The consequences are wide-ranging and affect both production and animal welfare.

Drop in milk production: Milk production can quickly decline by 10 to 25 percent due to dehydration.
Reduced feed intake: Cows that drink too little water also eat less, which further disrupts the energy balance.
Impaired rumen function: Water is essential for healthy rumen fermentation and microbial protein production.
Increased risk of ketosis and fatty liver: Reduced feed intake and a disrupted metabolism increase the likelihood of metabolic disorders.
Fertility problems: Heat stress combined with dehydration disrupts hormonal balance and reduces conception rates.
Greater susceptibility to infections: A weakened immune system makes cows more vulnerable to mastitis and other conditions.

The damage accumulates rapidly when drinking water is not sufficiently available or when its quality is inadequate. Early intervention is therefore essential.

How does heat stress affect water intake in dairy cattle?

Heat stress affects water intake in dairy cattle in several ways simultaneously. As ambient temperature rises, cows increase their breathing rate and sweat more to dissipate heat. This increased fluid loss stimulates thirst, causing cows to drink more frequently and in larger quantities. At the same time, feed intake decreases, disrupting the energy balance.

An important concept here is the Temperature Humidity Index (THI). From a THI value of 68, milk production and cow welfare begin to decline noticeably. At a THI above 72, clear heat stress is present, with water intake rising sharply and the cow struggling to regulate her body temperature.

Cows prefer to drink in short, intensive bouts immediately after milking. In hot weather, this drinking behavior becomes even more pronounced: they quickly seek out the water trough and consume large quantities at once. This places high demands on the capacity of drinking installations. When there are insufficient drinking stations or inadequate water supply, this can lead to competition and an uneven distribution of water intake within the herd.

What factors determine a cow’s water requirements in summer?

A cow’s water requirements in summer are determined by a combination of factors that together define the total daily need. There is no universal figure that applies to every cow, but the following factors play the greatest role in estimating the required amount of drinking water for cattle.

Milk production: The more milk a cow produces, the more water she needs. The ratio is roughly 4 to 5 liters of water per liter of milk.
Body weight: Heavier cows have a higher baseline water requirement for their metabolism and thermoregulation.
Ambient temperature and humidity: The combination of heat and humidity determines the severity of heat stress and therefore the additional water requirement.
Dry matter content of the ration: Cows that eat large amounts of dry roughage or concentrate feed need more drinking water than cows on fresh grass or silage with a high moisture content.
Stage of pregnancy: Pregnant cows, especially in the final stage of gestation, have a higher fluid requirement due to the growth of the fetus and placenta.
Health and stress level: Sick or stressed cows regulate their water intake less efficiently and are more susceptible to dehydration.

By considering these factors in combination, you as a livestock farmer can make a realistic estimate of the daily water requirement per animal and align your drinking water supply accordingly.

How do you ensure sufficient, high-quality drinking water during heat?

Providing sufficient, high-quality drinking water during heat requires a combination of the right infrastructure, management, and monitoring. It is not only about the quantity of water, but also about its accessibility and quality. Dirty, warm, or bacterially contaminated water is avoided by cows, which significantly reduces intake.

Practical measures to optimize the drinking water supply:

Ensure adequate drinking stations: at least one water trough per 15 to 20 cows, with a minimum water flow rate of 20 liters per minute per trough.
Place water troughs in multiple locations in the barn and on the yard, so that dominant cows cannot drive other animals away.
Clean water troughs daily during hot weather, as warm water promotes the growth of algae and bacteria.
Keep the water as cool as possible by placing troughs in the shade or insulating them.
Regularly check water pressure and supply capacity, especially during the hottest parts of the day when demand peaks.
Monitor water quality for pH, nitrates, and bacterial load, particularly in summer.

Cows drink the most in the 30 to 60 minutes after milking. By keeping the passage to the water troughs clear and eliminating any bottlenecks in the barn layout, you can significantly improve water intake per animal.

What role do electrolytes and betaine play in heat stress in cows?

Electrolytes and betaine play an important supplementary role in supporting cows during heat stress. While water covers the basic requirement, electrolytes such as sodium, potassium, and magnesium help restore fluid balance within cells and support muscle function. Betaine acts as a powerful osmolyte that protects cells against the negative effects of heat and dehydration.

Betaine is a natural ingredient derived from sugar beets that works at the cellular level. It helps cells maintain their fluid balance when the environment changes osmotically, as is the case during heat stress. In ruminants, betaine also supports rumen fermentation: it stimulates microbial protein production, improves fiber digestion, and has a positive effect on the production of short-chain fatty acids. This is relevant because feed intake and rumen function come under pressure during heat stress.

Scientific research confirms that betaine contributes to osmotic support in ruminants during heat stress, improving cell stability and therefore the overall stress resilience of the animal. Supplementary support via drinking water and feed additives is a practical and effective approach, especially since water intake during heat stress is more reliable than feed intake.

Want to learn more about how betaine works as an osmolyte and how it supports the stress resilience of your livestock? The scientific foundation is solid and the applications are wide-ranging.

How Jodoco helps with heat stress in cows

At Jodoco, we understand that heat stress in dairy cattle has a direct impact on production, health, and profitability. Our solutions are specifically developed to support livestock farmers with scientifically grounded, natural products that precisely address the physiological challenges of heat.

Specifically, we offer the following for cattle during heat stress:

Ruval Plus: A liquid source of natural betaine and organic acids that provides osmotic support during heat stress, stimulates rumen fermentation, and improves feed intake. VLOG-certified and palatable for better uptake.
Acibet G: Combines betaine with glycerol and organic acids for energy support, improved liver function, and increased feed intake, even in warm conditions.
Osmotic cell support via betaine: Our products based on natural betaine actively protect cells against the osmotic stress caused by heat, increasing the overall stress resilience of your cows.
Flexible administration via drinking water: Especially during heat stress, drinking water is a more reliable delivery vehicle than feed. Our liquid products dissolve easily in drinking water, ensuring controlled and consistent uptake.

Would you like to know which approach best suits your operation and your herd? Contact us via our contact page. Our specialists are happy to work with you on a targeted strategy for the summer of 2026.