Dairy producers have long recognized that bovine growth, reproduction and milk production depend on adequate feed intake. However, feed is only one component of proper nutrition.

The fluid intake demands of dairy cattle are equally important. Water deprivation, leading to dehydration, can have a severe impact on the health and performance of a herd. Unfortunately, water deprivation and dehydration aren’t always easy to detect because they can happen in both sick and healthy cows.

Most dairymen know the leading signs of disease. But they might not spot a cow that’s recently off feed — many times, an early sign of water deprivation. Most dairy facilities do not have a practical way to measure water or fluid intake by cattle on a daily basis.

In this article, we’ll look at the importance of water and fluids in maintaining the nutrition of dairy cattle.

Body fluid demands
Fluids, including water, comprise an average of 60 percent of the total bodyweight of the dairy animal. Young calves have about 5 to 10 percent more body fluids and adult cows about 5 to 10 percent less.

Of this total body fluid, 66 percent is found in the cells and the remaining third is found in the blood vessels, body linings and cavities outside the stomach or rumen.

The stomach in the young calf and the adult rumen serve as a reservoir which releases water to the body fluid compartments through osmotic pressure and suction-like action. As the cells require fluid for metabolism, the electrolytes and other digestive nutrients exert osmotic pressure to continuously supply the cells with fluid for normal functions.

A fluid or electrolyte deficit in the stomach, rumen or blood vessels, results in reduced transfer (perfusion) of fluids and nutrients to the cells for normal functions and metabolism. To maintain normal cellular functions, the average fluid or water maintenance intake rate is 40 to 60 milliliters of fluid per kilogram of bodyweight on a daily basis.

Converting to pounds and gallons, the average 100 pounds of bodyweight require 1.2 gallons (9.6 pounds) of water on a daily basis. If cattle consume 10 to 30 percent of their daily water needs from their ration, it would be essential that cattle would require a daily water volume intake of at least 8 to 9 percent of their total bodyweight.

Calves on dry feed, or only milk or milk replacer, should be fed at a minimum of 10 percent of their bodyweight in water or fluid. Lactating cows require an additional 85 to 90 percent of their total daily volume milk production in addition to the 8 to 9 percent of bodyweight water demands.

Water requirements for normal milk production for lactating cows or calves exposed to hot weather, running a fever or temperature require an additional 20 to 30 percent daily water intake for maintenance of body functions.

Water deprivation and dehydration
So what happens when calves and cows do not receive their daily water or fluid requirement?

Very limited research has been conducted with healthy animals, exposing them to water deprivation or dehydration to measure the impact on performance as it relates to immune response, reproduction, growth and milk production. But considerable data exists on the growth rate in calves encountering diarrhea and pneumonia, as well as the influence on diseases related to milk production in the lactating cow.

Recent research in Switzerland with healthy Brown Swiss cows measured the impact of 25 and 50 percent water deprivation over an eight-day period. These cows were fed and watered individually for 17 days.

For the first five days of the trial, the cows were fed and watered individually to determine their average individual daily weights or volumes of water and feed intake. Cows were then restricted by 25 and 50 percent of their normal water intake for eight days and then given or returned to their normal free-choice water intakes for the remaining four days.

The results shown in Table 1* demonstrate the effect of water intake on production. Both the 25 percent and 50 percent water-restricted animals were returned to their free-choice or ad libitum daily supply of water after the restriction period for four days.

Most cows returned to a slightly lower level of milk production than prior to their water-restriction period. The cows in this trial averaged 268 days into their lactation periods. No consideration was given to the possible impact of water restriction had the trial been conducted during the peak period of milk production the first 90 to 120 days after parturition or calving.

The researchers conducting the trial suggested that the cows seemed to have an inherent tendency to use the rumen reservoir to maintain a constant range or water-to-feed ratio. As water intake restriction was imposed in the trial, intake of feed which was available on a free-choice basis decreased inherently throughout the period of time of water restriction.

Cows receiving the restricted (both 25 and 50 percent) volumes of water immediately consumed their rations when some water became available. Feed consumption decreased during the 24-hour periods as their water source was restricted.

This trial would indicate that whenever cows drop in feed intake, consideration should be given to the cows being dehydrated or not consuming enough water to meet their daily body needs.

Water-electrolyte supplementation
Offering a sufficient free-choice or ad libitum supply of water should, in most cases, enable normal dairy animals to meet their body fluid needs. Cows crave water after calving or milking and will drink significant volumes of water after calving to replenish fluids lost while giving birth.

Providing electrolytes in the drinking water consumed after calving helps promote optimum osmotic pressures in the body fluid compartments to aid in the recovery from the dehydration or fluids lost during calving. Cows will consume 30 to 50 percent of their daily water intake shortly after milking – if available – to restore fluids released during milking.

By facilitating or enhancing water intake shortly after milking rather than delaying it, cows have a longer period of normal hydration prior to the next milking. With the immediate water intake after milking, cows are more likely to consume feed as shown in the Swiss trial.

Young calves suffering from diarrhea will consume more water or fluid if they are fed milk replacer three to four times a day. Many calves will not consume more than two quarts of water at one time.

By feeding a quarter of a pound of milk replacer in 1.5 to 1.3 quarts of water four times a day, the calf will consume 33 to 50 percent more water to combat dehydration than if given a half-pound of milk replacer in two quarts of water twice a day.

Most cows and calves that lose 3 to 8 percent of their bodyweight from dehydration can be rehydrated orally with added oral fluids and electrolyte/energy supplements.

Once the animal’s dehydration is more than 9 to 10 percent of their bodyweight, they will require intravenous and oral fluid supplementation to avoid slipping into a coma and dying. Animals are more prone to develop permanent body malfunctions from dehydration or water deprivation than they are from short periods of feed deprivation.

Dairy producers should always take action to provide additional sources of water and rehydration supplementation when they observe feed intake reduction or when animals show signs of body shrink and dehydration.

Signs of dehydration
Mother Nature provides, primarily, healthy cows with an inherent capability to withstand limited periods of water deprivation, without showing signs of dehydration. In the Swiss trial, mentioned earlier, although there was water deprivation, the only obvious physical signs of dehydration was limited to decreased feed intake, lower milk production and reduction in volumes of urine and fecal output.

Dairy producers should always recognize physical changes or symptoms, such as diarrhea, increased respiratory rate and elevated body temperature, as a sign of dehydration. These are body defense reactions that require additional body fluids and nutrients.

Cows encountering or suffering from displaced abomasums, rumen acidosis, metritis or retained placentas will encounter long-term losses in milk production, if the primary conditions and the associated dehydration are not treated and resolved.

I would recommend that dairy producers develop a program or protocol with their nutritionists and veterinarians to use whenever they observe symptoms of dehydration. With a standardized protocol, dairy producers will be able to minimize losses from many conditions commonly found in dairy operations. PD

Veterinarian Peter H. Franz is on the staff of Form-A-Feed Inc. and TechMix Inc., located in Stewart, Minnesota. For questions or more information, call (800) 422-3649 or send an e-mail to articleinfo@techmixinc.com.

*Tables and photos were omitted from this article but are available upon request at editor@progressivedairy.com.