REHYDRATION REDEFINED: Smarter Electrolyte Support for Scouring Calves

Dr Geoff Irish
Apr 27
6 min read

New formulation, developed by Dr Geoff Irish, PhD, B.Ag.Sc. (1st Class Hons), combines practical on-farm application with advanced electrolyte science to support rapid calf recovery.

UMMER 2026

Introduction

Young calves are around 70–75% water by bodyweight and must be well-hydrated in order to stay healthy and grow to their full potential. Dehydration and severe electrolyte loss in calves can stem from several causes including inadequate water intake and heat stress. However, the main culprit to dehydration is often due to bouts of diarrhoea, more commonly called scours, which can cause calves to lose 5-12% of their bodyweight as water.

Neonatal calf diarrhoea is still a leading cause or mortality and economic loss in the dairy industry. Recent data indicates that over 60% of dairy calf deaths in the U.S. are attributed to diarrhoea. When calf diarrhoea hits, it is critical to reverse the effects of dehydration to avoid metabolic acidosis, weakness, severe weight loss, and potential mortality.

Oral rehydration by electrolyte therapy is an effective way to reverse the symptoms of dehydration and correct electrolyte imbalances.

What Are Electrolytes?

Electrolyte products typically include a combination of sodium, energy, amino acids and alkalizing agents designed to support rapid recovery and get calves back on their feet. Electrolyte therapy is a common management practice used to replenish fluids and combat metabolic problems in a dehydrated calf, including acidosis and electrolyte losses associated with diarrhoea.

When Should Electrolytes Be Provided?

Calves can lose 5 to 10% of their body weight in water within 1 day of scouring. Fluid loss in excess of 8% requires IV treatment, and over 14% loss can result in death (Figure 1).

Early detection and prompt treat are essential. Daily monitoring is critical and treat them quickly when signs of illness are observed. The amount of water lost by scouring calves can be approximated using symptoms such as skin tenting, gum condition, attitude, and ability to stand or suckle (Table 1).

Figure 1. Visual representation of percent dehydration as related to clinical symptoms and health of calves. (Adapted from M. A. Wattiaux (2005); Electrolytes For Dairy Calves, PennState University.)

To evaluate hydration using skin tenting, pinch a fold of skin (best done on the neck) and count the seconds it takes to flatten. Flattening of skin in less than 2 seconds indicates normal hydration. If skin takes 2 to 6 seconds to flatten, the calf is about 8% dehydrated. Over 6 seconds indicates severe dehydration above 10%.

Gums can be evaluated by looking at their colour and feeling them for moisture. Normal gums should be pink and damp but if gums are white and dry this indicates 8 to 10% dehydration.

One of the best measures of estimated dehydration and illness in calves is their attitude during milk feeding. Calves may show no symptoms of dehydration but if they need encouragement to drink, monitor them closely for scouring or other illnesses.

Table 1. Clinical symptoms that help evaluate the level of dehydration in calves.

Dehydration %	Symptoms
5 - 6 %	Diarrhoea; no clinical signs; strong suckling reflex
6 - 8 %	Milk depression; skin tenting 2 to 6 seconds; calf still suckling; sunken eyes; weak
8 - 10 %	Calf depressed, laying down; eyes very sunken; dry gums; skin tenting > 6 seconds
10 - 14 %	Calf will not stand; cool extremities; skin will not flatten when tented; comatose
> 14%	Death

(Adapted from J. M. Naylor, Can. Vet. J.; Electrolytes For Dairy Calves, PennState University.)

Should Milk Be Feed While Calves Are Scouring?

Scouring calves lose water and nutrients faster than their non-scouring counterparts, and require the liquid and nutrients provided by their milk feedings. Calves need enough energy to maintain their weight as well as their immune system, especially when they are sick.

Electrolyte solutions cannot provide enough energy because they are limited in the amount of glucose that can be added in order to keep the osmolarity of the solution low. Therefore, feeding milk or milk replacer, supplies more energy and protein, allowing calves to maintain weight.

One of the studies showing the benefit of milk feeding while treating with rehydration solution was conducted at the University of Illinois (Figure 2). Once scouring occurred, calves were placed onto 3 different treatments. Treatment 1 consisted of only rehydration solution fed for 2 days, after which milk was slowly incorporated back into the diet for 7 days. Treatment 2 consisted of a partial removal of milk during therapy, and treatment 3 was a full feeding of milk as well as rehydration solution for 7 days. Importantly, faecal scores did not differ between treatments and body weights were higher for the treatments that incorporated milk in some way, reinforcing the benefit of continuing milk feeding during the entire treatment period.

Figure 2. Treatment 1 was oral rehydration solution (ORS) only, treatment 2 was ORS with low feeding of milk and treatment 3 is equal ORS and milk feedings. (Adapted from Garthwaite et al. (1994) Journal of Dairy Science Vol. 77. No.3. 1994)

What Should The Oral Rehydration Solution Contain?

Water: One of the most important components of oral rehydration solutions. Water forms the foundation of any effective rehydration solution.

Sodium: Essential for fluid balance. Dehydrated calves secrete sodium, and this mechanism can be exacerbated in the presence of Salmonella and E. Coli. Water and sodium are closely linked, and water follows where sodium goes; thus, sodium absorption in the small intestine also promotes water absorption.

Energy Source: A simple sugar, such as dextrose (glucose), provides quick energy to the calf and assists with sodium absorption through the small intestine.

Glycine: This is a non-essential amino acid that assists glucose absorption. Rehydration is key when considering a dehydrated calf. Sodium, glucose and glycine are all tied together and play a key role in the water uptake mechanism of the small intestine.

Alkalizing Agents: These are added to help reverse any metabolic acidosis that may be occurring within the calf. Acetate, propionate, and bicarbonate are all considered alkalinizing agents and are frequently present in commercial oral electrolyte solutions. Bicarbonate-containing fluids are effective at correcting a severe acidosis, because bicarbonate reacts directly with H⁺ ions to form CO₂ and H₂O. Acetate and propionate are also alkalinizing agents and have been shown to have alkalinizing effects similar to bicarbonate. Acetate and propionate have several advantages over bicarbonate:

Acetate and propionate facilitate sodium and water absorption in the calf small intestine, whereas bicarbonate does not.
Acetate and propionate produce energy when metabolized, whereas bicarbonate does not.
Acetate and propionate do not alkalinize the abomasum, whereas bicarbonate does; low abomasal pH is a natural defence mechanism against bacterial proliferation.
Acetate and propionate do not interfere with milk clotting in calves, whereas bicarbonate may potentially cause some disturbance of the normal digestive process

Electrolytes: Oral rehydration solutions will also contain other electrolytes, especially potassium and chloride. Calves lose some potassium and chloride due to diarrhoea. Potassium and chloride are included in order to maintain blood pH and for muscle contractions, especially in the heart.

Strong Ion Difference (SID): The loss of a large amount of sodium and potassium when a calf scours can result in metabolic acidosis – a drop in blood pH. A calf is not able to correct acidosis without intervention. For moderate acidosis, calf electrolyte products with a high SID formulation can help balance the loss. The SID can be calculated as follows:

[Na⁺] + [K⁺] - [Cl^-] = SID.

If the metabolic acidosis is too severe, oral electrolytes cannot make the correction alone and the calf will need intravenous therapy.

Osmolality: Commercially available oral electrolyte products can range from isotonic (280–300 mOsm/L) to extremely hypertonic (700–800 mOsm/L). The primary difference in most of these products is the amount of glucose that is added. As a result of a counter-current exchange mechanism in the small intestine, the effective osmolality at the tip of the intestinal villus is about 600 mOsm/L. We can therefore take advantage of hypertonic solutions that have higher energy levels. On the other hand, low osmolality fluids (<350 mOsm/L) generally have inadequate energy content because they have insufficient glucose. Hypertonic solutions provide greater nutritional support to calves relative to isotonic products and have not been shown to cause detrimental effects, particularly in relation to maintaining hydration status, intestinal osmolality, serum glucose concentrations, and intestinal flow rate. Extremely hypertonic oral electrolyte product (>700 mOsm/L) should be avoided. High osmolality can slow absorption of beneficial electrolyte solution ingredients and in some cases make diarrhoea worse.

Why Choose Hydra-TRAC?

Hydra-TRAC is one of only a few products available that does not contain sodium bicarbonate and can be fed directly before or after milk, rather than having to wait a few hours.

Early intervention is key to raising strong, healthy calves. Hydra-TRAC supports rapid rehydration and recovery, helping calves return to optimal health sooner.

Keep Hydra-TRAC on hand for convenient daily use as part of a proactive calf management program. New formula by Dr Geoff Irish – now available in 9 kg and 18kg bagged and sealed buckets.

Important Note: Severe dehydration in calves (typically >8-10% dehydration) is a medical emergency. Rapid deterioration can occur, and immediate veterinary intervention is essential.

If you have any questions, please do not hesitate to talk with one of our TRAC Ruminant Experts on 08 8733 1888 or email us at info@totalresult.com.au.