by Alison Pfau

Water is an important nutrient, and animals require it in larger amounts compared with humans. Water contributes 75% of a calf’s body weight, making this nutrient an essential daily requirement. The amount of water consumed by an animal depends on its size, milk production, environmental temperature, and feed and mineral intake.

Providing an adequate amount of water for dairy calves is often an overlooked aspect in calf management programs. Water is necessary for various biological functions, including a calf’s metabolism.

When calves are born, their body is made up of 70% water, while their body fat percentage is 3% to 5%. An opposite relationship exists between body water and body fat. So as an animal grows and deposits more fat, that fat takes the place of water.

However, a critical factor for young calves is that when they have diarrhea, they immediately lose body water. If they lose around 4% of body water, their osmo-receptors react to encourage them to drink more water. However, if body water loss increases to 8% to 10%, intravenous or oral treatment such as electrolyte solution is necessary to ensure adequate hydration.

Rumen development

Water serves a crucial function by aiding in rumen development. Rumen microorganisms require water to ferment effectively. Water dilutes volatile fatty acids produced by the rumen. This enables bacteria to generate additional VFAs, which in turn provide essential nutrition to the animal and support papillae growth in the rumen. If there is a shortage of water, these microbes cannot thrive, leading to decreased VFA production.

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Milk replacer and whole milk contain water, but the amount is not sufficient to boost calf starter consumption. In addition, the majority of the water consumed from milk sources does not enter the rumen and thus is unable to assist with facilitation of the environment required for bacteria growth due to the stage of rumen development at this age. Therefore, offering water freely is the optimal approach.

Having access to water at all times enhances starter intake and weight gain, particularly in terms of muscle and skeletal development during the initial two months of life. This, in turn, is positively associated with milk yield during the first lactation.

For more information about rumen development in calves, see dairy.extension.wisc.edu.

Another important correlation exists between dry matter intake and water intake. If water intake is limited, dry matter intake may be limited as well. For this reason, calves need four times more water than dry matter intake.

Ruminants use water to transport nutrients throughout the body, and it is involved in every aspect of the calf’s metabolism. Water is also needed to regulate body temperature and eliminate waste. According to research recommendations, the overall ratio of water to dry matter intake is about 4-to-1. This further highlights the importance of providing clean, fresh water for calves at all times.

Water temperature

Another important factor is water temperature. Calves like warm water, especially in the wintertime. Cows even preferred warm ambient water (86 degrees F vs. 50 degrees F) in hot summer conditions based on a literature recommendation. Research indicates that before weaning, calves tend to consume more water when the water is warm compared to when it is cold.

After drinking water at a temperature of 45 degrees, it takes about an hour for the temperature of the rumen to return to nearly normal levels. Providing water with temperatures of 63 degrees, 81 degrees and 99 degrees can produce less of a drop in rumen temperature, but it still requires about an hour for the rumen to return to normal.

In winter weather, water remains critical for calves. With each breath, a calf exhales more moisture into the drier, colder winter air than it inhaled, which leads to losing more body water with each breath compared to warmer air conditions like spring or summer. Providing warm water to calves during cold temperatures benefits calves by not requiring their body to use additional energy to warm colder water to rumen temperature.

Pfau is a University of Wisconsin Extension bilingual regional dairy educator.