The Role of Water in Dairy Cows

Water is often the most underestimated yet most critical factor in the nutrition of dairy cows. Without an adequate supply of clean, good-quality water, no feeding program—no matter how well-balanced—can be truly effective. Water availability determines not only the quantity and quality of milk but also the animal’s overall health, reproduction, and welfare.

Water as the Main Component of Milk

Milk is composed of 85–88% water, making it the most essential element. Water serves as the transport medium for all nutrients—lactose, proteins, fats, minerals, and vitamins—from the cow’s bloodstream to the udder, where milk is formed.

This process depends on the osmotic balance created by lactose, which draws water into the mammary cells. Therefore, even a small reduction in water intake can lead to a significant decrease in milk production, as blood flow and nutrient supply to the udder are reduced. To produce 1 liter of milk, a cow needs 3 to 5 liters of water. This ratio clearly shows that water is not merely a supporting factor but the main regulator of production.

Why Water Is So Essential

Water is vital for all life-sustaining functions of the cow’s body. It participates in every metabolic, digestive, and thermoregulatory process. Specifically, it:

• Regulates body temperature through sweating and respiration.

• Transports nutrients (proteins, sugars, minerals, vitamins) from the digestive system to the organs and the udder.

• Facilitates digestion and fermentation in the rumen, where fibrous feeds are broken down.

• Supports blood circulation, ensuring the delivery of energy and nutrients to the cells.

• Enables the excretion of toxins and metabolic waste through urine and feces.

When water is lacking, the entire organism becomes unbalanced. Insufficient quantity or poor water quality leads to reduced feed intake, decreased milk yield, and metabolic disorders.
Research has shown that a 10% reduction in water intake can result in a 15–25% drop in milk production.

Factors Affecting Water Intake

The amount of water a cow consumes depends on several factors:

• Ambient temperature: The higher the temperature, the greater the water requirement.

• Type and dry matter of the feed: Silage contains moisture, while dry rations increase the need for drinking water.

• Level of milk production: Each additional liter of milk requires approximately 4 liters of water.

• Water quality: Taste, temperature (ideally 17–25°C), and cleanliness are crucial.

• Health and physiological condition: Sick or stressed animals drink less water.

Poor-quality water (high in salts, iron, or microorganisms) can negatively affect appetite and cause digestive or metabolic problems. Therefore, regular water-quality testing is essential for maintaining optimal herd performance and milk yield.