Feeding Pre-weaned Calves, Part 3: Water

Dr. Grazyne Tresoldi, Assistant Professor, Animal Welfare, Department of Animal Sciences, The Ohio State University

In Part 2 of this series, we discussed how expanding your milk program shifts your calf management from a daily expense to a long-term investment. We teased that our next focus would be the solid diet. However, as the summer heat approaches, we must first address the most critical nutrient on the dairy: water.

From an animal welfare standpoint, providing unrestricted access to fresh water is the absolute baseline of care. In addition, water is also a primary driver of biological functioning; free-choice water is essential to optimal metabolism. For example, it helps calves cope with summer heat and is the ultimate catalyst for rumen development and starter intake.

Do calves spontaneously drink water?

Absolutely! Precision automated water monitoring shows that calves spontaneously explore and drink water from a very early age, some as early as 4 days of age. While individual calf personalities and social imitations cause wide variations in drinking behavior, providing access to water from Day 1 will stimulate calves to get used to the water source and encourage early drinking habits. In pair- or group-housing systems, this social imitation provides a clear welfare benefit: timid calves actively learn to drink by copying their bolder pen-mates.

Calves provided with ad libitum water from birth consume starter feed earlier and achieve significantly higher body weight gains compared to calves where water is withheld. In fact, research shows that withholding supplemental water results in a 31% reduction in starter intake and a massive 38% reduction in body weight gain. By weaning at 9 weeks, high-performing calves can routinely consume 5 or more quarts of free water per day.

The Role of Water on Calf Metabolism

Nutrient digestion and rumen development

While many may think that milk provides enough hydration for a young calf, there are fundamental differences in how their bodies process these liquids. In fact, research indicates a positive correlation between milk volume and water intake: calves on a generous, optimized milk feeding program actually drink significantly more water spontaneously than calves on restricted milk diets. This is because water and feed intake are positively associated; when one is compromised, the other follows because every single metabolic process in the body requires an aqueous environment.

When a calf drinks milk or replacer, a natural muscular fold called the esophageal groove acts like a closed pipeline. This pipeline reflexively routes the liquid past the rumen, sending it directly into the true stomach (the abomasum) for enzymatic digestion. Therefore, the liquid from milk does not enter the rumen.

Conversely, rumen microorganisms require an entirely separate, watery environment to ferment dry starter grain. Research shows that providing early access to drinking water directly accelerates dry feed consumption, increases the apparent total-tract digestibility of fiber components, and ensures rapid, healthy development of the rumen wall. This early microbial development drives superior fiber digestion post-weaning, unlocking the vital nutrients needed to fuel the calf's structural skeletal growth.

Heat abatement

Despite young calves having a high surface-area-to-body-mass ratio and producing relatively less metabolic heat than mature cows, they are highly susceptible to heat load because their bodies are still developing. When dealing with heat, calves must redistribute energy away from growth toward temperature regulation.

The most effective way for a calf to lose heat is through increased respiration rates and panting, which accelerates moisture loss through evaporation. To compensate for this loss and maintain blood acid-base chemistry, a calf's physiological water demand spikes dramatically. Research shows that when environmental temperatures rise from 82 to 91°F, a calf’s water intake increases by 23% just to maintain basic bodily functions.

In a field study we conducted in Ohio dairy farms, we found that housing choice heavily dictated this physiological workload. Calves housed in hutches experienced a much sharper increase in respiration rates compared to those in pens, specifically, an increase of 4 versus 1 breaths/minute for every 1-degree Fahrenheit rise in ambient temperature. Even with vents open and water refills, calves averaged 89 breaths/minute across dairy farms. This indicates they were working incredibly hard to dissipate heat.

How should water be provided?

When setting up a water delivery system, producers frequently wonder if they should use open buckets or nipple/teat-based waterers. While calves may visit nipple-based water sources more frequently due to their natural instinct to suckle, biologically, calves are suction drinkers. Research demonstrates that their actual total daily water consumption is higher when water is provided in an open bucket or pail. Open buckets also offer a significant practical advantage for farm labor: they are far easier to thoroughly wash, rinse, and sanitize to prevent biofilm accumulation.

Just like mature cows, a calf's voluntary water intake is directly tied to the quality of the fluid provided. If water looks, smells, or tastes unpalatable, calves will refuse to drink enough of it. To optimize consumption:

• Rinse buckets daily to remove grain dust, saliva, and organic buildup. Keep them clean, as manure contamination can decrease water intake by up to 28%.
• Keep calf drinking water within an optimal pH range of 6.5 to 8.5.
• Provide water with a total dissolved solids (TDS) level below 1,000 ppm, as it is highly palatable for young calves.
• Pay attention to seasonal preferences: calves prefer warm or lukewarm water (100 to 104°F) during the winter and cool water (50 to 70°F) during the summer. Changing water temperature to a comfortable, palatable range can swing a calf's voluntary water intake by nearly 50%.

Dehydration: identification and rehydration

If calves do not meet their water requirements, or if they face heavy fluid losses from summer heat load or scours, dehydration can quickly become life-threatening. Recognizing the warning signs early is critical for calf survival.

• Signs of severe dehydration (≥10% fluid loss) are obvious and critical. They include deeply sunken eyes (a distinct gap between the eyeball and the eyelid), cold ears, dry muzzle, and the calf may be unable to stand.
• Mild to moderate signs are much more subtle and must be assessed using the skin tent test. To perform this, pinch a fold of skin on the side of the calf’s neck, twist it slightly, and release it immediately. In a healthy, hydrated calf, the skin snaps back flat in less than 1 second. If the skin takes 2 to 5 seconds to flatten out, the calf is moderately dehydrated and requires immediate intervention.

Administering oral rehydration solutions (electrolytes) is the standard therapy to restore blood water, minerals, and acid-base balance. A study conducted by Ohio State researchers evaluated hydration protocols and found that providing calves with oral electrolytes for 2 consecutive days significantly improved biochemical measures of hydration and accelerated recovery from moderate dehydration.

When executing a rehydration protocol, keep these golden rules in mind:

• Choose an electrolyte solution that uses acetate or propionate rather than bicarbonate as an alkalinizing agent. Bicarbonate raises the pH of the abomasum and disrupts milk clotting, which can destroy the calf's natural acidic defense against pathogens. Acetate and propionate correct metabolic acidosis without interfering with these natural defenses.
• Electrolytes must always be mixed separately in warm water according to manufacturer guidelines. Mixing electrolyte powder directly into milk or replacer creates a dangerously hypertonic solution that pulls water out of bodily tissues into the gut, delaying stomach emptying and triggering severe abomasal bloat.
• Maintain the regular milk feeding schedule so calves still receive the vital energy to fuel their immune systems and repair their gut linings.
• Deliver the oral electrolyte solutions as an additional, separate meal between regular milk feedings, making sure meals are spaced at least 2 hours apart to ensure proper abomasal passage.

Take-home messages (Table 1):

• Water is a fundamental welfare and metabolic requirement; withholding it causes a 31% drop in starter intake and a 38% drop in weight gain.
• Offer clean, free-choice water immediately from Day 1 of life to stimulate early drinking habits.
• Maximize total volume intake by using buckets, which align with the calf's biology as a suction drinker and are significantly easier to keep clean compared to nipple systems.
• Avoid the 28% intake penalty by rinsing buckets daily to eliminate manure and organic buildup.
• Catch dehydration early before eyes sink. A neck skin tent lasting 2 to 5 seconds means it is time to intervene.
• Avoid the bicarbonate trap: Choose electrolyte solutions utilizing acetate or propionate to protect the calf's natural abomasal defenses against scours.
• When feeding electrolytes, always mix them in water and provide them as an extra meal in between normal milk feedings to avoid dangerous hypertonicity.

Table 1. Key Benchmarks: Hydration

Selected References

Huuskonen, A., L. Tuomisto, and R. Kauppinen. 2011. Effect of drinking water temperature on water intake and performance of dairy calves. Journal of Dairy Science 94(5), 2475-2480. https://doi.org/10.3168/jds.2010-3723

Jensen, M.B., and M. Vestergaard. 2021. Invited review: Freedom from thirst—Do dairy cows and calves have sufficient access to drinking water? Journal of Dairy Science 104(11), 11368–11385. https://doi.org/10.3168/jds.2021-20487

Kertz, A.F., L.F. Reutzel, and J.H. Mahoney. 1984. Ad libitum water intake by neonatal calves and its relationship to calf starter intake, weight gain, feces score, and season. Journal of Dairy Science 67(12), 2964-2969.

Lowe, G.L., M.A. Sutherland, M. Stewart, J.R. Waas, N.R. Cox, and K.E. Schütz. 2022. Effects of provision of drinking water on the behavior and growth rate of group-housed calves with different milk allowances. Journal of Dairy Science 105(5), 4449–4460. https://doi.org/10.3168/jds.2021-21304

Pempek, J.A., Z. England, G.G. Habing, and A. Niehaus. 2024. Rehydration post-transport: Duration of oral fluid therapy on behavior, biochemical measures of hydration, and health of neonatal dairy calves. Journal of Animal Science 102, 1-10. https://doi.org/10.1093/jas/skae011

Senevirathne, N.D., J.L. Anderson, P.S. Erickson, and M. Rovai. 2021. Evaluation of the effects of water quality on drinking preferences of heifer calves. JDS Communications 2(6), 393–397. https://doi.org/10.3168/jdsc.2021-0101

Smith, G.W. 2009. Treatment of Calf Diarrhea: Oral fluid therapy. Veterinary Clinics of North America: Food Animal Practice 25(1), 55-72. https://doi.org/10.1016/j.cvfa.2008.10.006

Staub, C., and E. Venturi. 2026. Do calves drink water? Animals 16(7), 997. https://doi.org/10.3390/ani16070997

Wickramasinghe, H.K.J.P., A.J. Kramer, and J.A.D.R.N. Appuhamy. 2019. Drinking water intake of newborn dairy calves and its effects on feed intake, growth performance, health status, and nutrient digestibility. Journal of Dairy Science 102(2), 377-387. https://doi.org/10.3168/jds.2018-15579