How Should Calf Scours Be Treated? Oral Electrolytes, IV Fluids and Emergency Signs

By Dr Duncan Houston

Two calves can produce equally watery diarrhoea and require completely different treatment.

One may still be standing, alert and sucking strongly. That calf can often recover with oral electrolytes, continued milk and close monitoring. The other may be weak, cold, unable to stand and no longer willing to suck. That calf is likely to be significantly dehydrated and acidotic and needs intravenous fluid therapy urgently.

The real concern is not simply the diarrhoea. It is whether dehydration, metabolic acidosis, electrolyte abnormalities, hypoglycaemia or sepsis are beginning to compromise the calf’s circulation, brain and muscles.

Quick Answer

A scouring calf that remains standing, alert and willing to suck can usually receive a calf-specific oral electrolyte solution in addition to its normal milk intake.

A calf that cannot stand, has a weak or absent suckle reflex, has eyes recessed approximately 4 mm or more, feels cold or is becoming minimally responsive needs urgent veterinary assessment and intravenous fluids, usually including sodium bicarbonate to correct metabolic acidosis. Antibiotics should be reserved for calves showing systemic illness rather than given automatically for diarrhoea alone. (PubMed Central (PMC))

Calf Scours Treatment at a Glance

Calf assessment	Most appropriate response
Standing, alert, strong suckle, no obvious eye recession	Continue milk and begin oral electrolytes
Standing but depressed, mild eye recession, weaker suckle	Oral electrolytes, close reassessment and same-day veterinary advice
Eye recession around 4 mm or more	Intravenous fluids are generally indicated
Unable to stand without assistance	Urgent intravenous fluid therapy
Weak or absent suckle reflex	Intravenous fluids rather than relying on oral treatment alone
Cold ears or limbs, low body temperature, poor circulation	Emergency stabilisation and warmed IV fluids
Severe ataxia, head pressing or altered awareness	Suspect marked acidosis, D-lactataemia, hypoglycaemia or sepsis
Blood or mucus in faeces, fever, pneumonia, joint or navel disease	Investigate systemic bacterial disease and antimicrobial need
No improvement after several hours of treatment	Reassess the diagnosis, fluid volume, acidosis and sepsis risk

The most useful field decisions are based on the calf’s ability to stand, strength of the suckle reflex, degree of eye recession and overall mental status. (PubMed Central (PMC))

What Is Calf Scours?

Calf scours is the common term for diarrhoea in young calves. It is a clinical syndrome rather than one specific disease.

Possible causes include:

• Enterotoxigenic Escherichia coli

• Rotavirus

• Bovine coronavirus

• Cryptosporidium parvum

• Salmonella

• Coccidia in older calves

• Mixed infections

• Feeding and milk-replacer errors

• Poor sanitation

• Failure of passive transfer

• Cold stress or other systemic disease

The pathogen damages the intestinal lining or changes intestinal secretion and absorption. Water, sodium, chloride, potassium and bicarbonate are then lost into the faeces faster than the calf can replace them.

Diagnostic testing must be interpreted carefully. Multiple pathogens are frequently found in the same calf, and organisms can also be detected in calves without clinical diarrhoea. The result must match the calf’s age, clinical signs, herd history and intestinal lesions. (Cal DFA)

What Actually Kills a Scouring Calf?

Dehydration and Loss of Circulating Volume

Watery diarrhoea can result in enormous fluid losses. In severe cases, daily faecal fluid loss may approach a substantial percentage of the calf’s body weight.

As extracellular fluid volume falls:

• Venous return decreases

• Cardiac output declines

• Kidney perfusion falls

• Urine production decreases

• Extremities become cold

• Tissue oxygen delivery deteriorates

• Shock develops

A calf can lose several litres of fluid before the producer realises how severe the deficit has become. (PubMed Central (PMC))

Metabolic Acidosis

Diarrhoeic calves often develop metabolic acidosis because of:

• Loss of bicarbonate in the faeces

• Reduced kidney excretion of acids during dehydration

• Accumulation of D-lactate

• Altered sodium and chloride balance

• Reduced tissue perfusion

D-lactate is particularly important in calves showing neurological-looking signs such as ataxia, weakness, abnormal posture, reduced awareness and loss of the suckle reflex. The calf may look much more depressed than the apparent dehydration alone would suggest. (PubMed Central (PMC))

Electrolyte Abnormalities

Diarrhoeic calves lose sodium, chloride and potassium through the intestinal tract.

The potassium picture is complicated. Total body potassium is usually depleted because of diarrhoea and reduced milk intake, but the measured blood potassium may be high in severely dehydrated and acidotic calves. This is one reason potassium should not be added casually to intravenous fluids without considering perfusion, urine production and laboratory findings. (PubMed Central (PMC))

Hypoglycaemia and Negative Energy Balance

Calves with diarrhoea often consume less milk while using more energy to maintain body temperature and immune function.

Critically ill calves may become hypoglycaemic, particularly when they are young, cold or have not eaten for an extended period. Hypoglycaemia is associated with poorer survival, and a veterinarian may add glucose to the initial fluid plan when indicated. (PubMed Central (PMC))

Bacteraemia and Sepsis

The initial cause of diarrhoea may be viral or protozoal, but damage to the intestinal barrier can allow bacteria to enter the bloodstream.

Calves with severe depression, abnormal temperature, absent appetite, pneumonia, joint swelling, navel infection or blood and mucus in the faeces are more concerning for systemic bacterial disease. These calves may benefit from parenteral antimicrobial treatment in addition to fluid therapy. (PubMed Central (PMC))

How Do You Assess Dehydration in a Scouring Calf?

The most useful on-farm assessment combines several findings rather than relying on the skin tent alone.

1. Can the Calf Stand?

A calf that stands independently is usually less acidotic and circulatorily compromised than one that remains recumbent.

Test a recumbent calf by helping it into a standing position:

• A calf that stands and remains upright has a better outlook.

• A calf that rises but immediately collapses is seriously compromised.

• A calf that cannot stand needs intravenous treatment.

Ability to stand is one of the central branches in validated calf-fluid decision trees. (PubMed Central (PMC))

2. How Strong Is the Suckle Reflex?

Place one or two clean fingers into the calf’s mouth.

Strong suckle

The calf grips firmly and repeatedly pulls against the fingers.

Weak suckle

The calf makes occasional, poorly coordinated sucking movements.

Absent suckle

The calf does not grip or suck.

A weak or absent suckle is a major warning sign of acidosis, D-lactataemia, hypoglycaemia or severe systemic illness. An absent suckle reflex should not be managed by repeatedly tubing fluids while waiting for the calf to improve. Intravenous resuscitation is generally required. (PubMed Central (PMC))

3. How Sunken Are the Eyes?

Gently pull the lower eyelid down and estimate the gap between the normal lower eyelid position and the corneal surface.

Eye recession, also called enophthalmos, is one of the most useful physical indicators of dehydration.

As a veterinary field estimate:

Approximate dehydration percentage = eye recession in millimetres × 1.6

For example, 4 mm of eye recession corresponds roughly to 6% to 8% dehydration and is commonly used as a threshold for intravenous treatment.

This formula is less reliable in chronically thin or cachectic calves because reduced orbital fat can also make the eyes appear sunken. (AVMA Journals)

4. How Long Does the Neck Skin Tent Remain?

Pinch a fold of skin over the side of the neck, rotate it approximately 90 degrees and release it.

Measure how long the fold takes to disappear.

• Immediate return is reassuring.

• A persistent fold suggests dehydration.

• A fold remaining for several seconds is concerning.

• A fold remaining for 5 to 10 seconds indicates severe fluid loss.

Neck skin tenting is more useful than testing loose skin over the shoulder or eyelid. (AVMA Journals)

5. Are the Ears and Limbs Cold?

Cold ears, cold fetlocks and a widening difference between core and peripheral temperature suggest reduced cardiac output and poor circulation.

Compare the calf with a healthy calf in the same environment. Cold extremities in a depressed scouring calf substantially increase concern, particularly when accompanied by pale mucous membranes or recumbency. (Frontiers)

6. What Is the Mental Status?

Assess whether the calf is:

• Bright and responsive

• Quiet but responsive

• Depressed

• Ataxic

• Recumbent

• Minimally responsive

• Comatose

Mental depression may reflect dehydration, acidemia, D-lactataemia, hypoglycaemia, sepsis or a combination of these abnormalities.

Do not assume a severely ataxic calf is simply weak from missing one milk feeding. (PubMed Central (PMC))

Practical Dehydration Guide

Estimated dehydration	Typical findings	General route
Less than 6%	Standing, alert, minimal eye recession, normal skin return	Oral electrolytes
6% to 8%	Depressed, eyes recessed 2 to 4 mm, skin tent 1 to 3 seconds	Oral electrolytes with close reassessment
8% to 10%	Weak, eyes recessed 4 to 6 mm, skin tent 2 to 5 seconds	Intravenous fluids usually required
10% to 12%	Recumbent or severely depressed, eyes recessed 6 to 8 mm, prolonged skin tent, cold extremities	Emergency IV fluid therapy
More than 12%	Moribund, severely shocked or dead	Critical emergency

These values are approximate. The calf’s ability to stand, suckle and respond remains as important as the estimated percentage. (news.okstate.edu)

How Worried Should You Be?

Lower Risk

The calf:

• Remains standing

• Is alert

• Suckles normally

• Has no obvious eye recession

• Continues nursing or drinking milk

• Has only recently developed loose faeces

Action: Begin oral electrolytes promptly, continue milk, provide fresh water and reassess within four to six hours.

Moderate Concern

The calf:

• Is quieter than normal

• Has mildly sunken eyes

• Has a weaker suckle

• Takes longer to rise

• Drinks less milk

• Has persistent watery diarrhoea

Action: Begin oral electrolytes and contact the herd veterinarian the same day. Reassess several times during the day. Escalate if the calf’s suckle weakens, eye recession increases or standing becomes difficult.

High Concern

The calf:

• Needs help standing

• Has a weak or absent suckle

• Has eyes recessed about 4 mm or more

• Has cold ears or feet

• Has marked ataxia

• Refuses milk

• Has become significantly dehydrated

Action: Arrange urgent intravenous fluid therapy. Oral electrolytes alone are unlikely to correct the problem quickly enough.

Critical

The calf:

• Cannot stand

• Is laterally recumbent

• Has minimal response to stimulation

• Has no suckle or palpebral reflex

• Is severely hypothermic

• Has open-mouth or markedly laboured breathing

• Has a distended abdomen

• Is passing blood or large amounts of mucus

• Is having seizures

• Is rapidly deteriorating

Action: Obtain emergency veterinary treatment immediately. The calf may need warmed IV bicarbonate-containing fluids, glucose, antimicrobial treatment, oxygen, warming and intensive monitoring.

When Is Calf Scours an Emergency?

Treat the situation as an emergency when the calf:

• Cannot stand

• Has an absent suckle reflex

• Has approximately 4 mm or greater eye recession

• Feels cold or has a low rectal temperature

• Is severely ataxic or minimally responsive

• Refuses all milk

• Produces little or no urine

• Has blood or mucus in the faeces with systemic illness

• Has joint swelling, navel infection or pneumonia

• Becomes bloated after oral treatment

• Fails to improve within several hours

• Is one of several rapidly deteriorating calves in an outbreak

A down calf should not be left until the following morning simply because oral electrolyte powder has been administered. (PubMed Central (PMC))

What To Do Right Now

1. Isolate the Calf

Move the calf into a clean, dry, sheltered area when this can be done without excessive stress.

Use separate:

• Feeding equipment

• Stomach tubes

• Buckets

• Bedding tools

• Boots and protective clothing

Several important causes of calf scours are highly contagious, and Cryptosporidium, Salmonella and some E. coli strains can also infect people. (Cal DFA)

2. Assess Standing, Suckle and Eye Recession

These findings determine whether oral treatment is reasonable or intravenous treatment is needed.

Do this before automatically reaching for antibiotics.

3. Keep the Calf Warm and Dry

Replace wet bedding and protect the calf from wind, rain and cold surfaces.

A cold calf has higher energy requirements and a poorer response to oral therapy. Do not apply excessive direct heat to a weak calf that cannot move away.

4. Continue Access to Milk and Water

Do not remove milk simply because the calf is scouring.

Milk supplies substantially more energy and protein than oral electrolyte solutions and supports intestinal repair. Fresh water should also remain continuously available. (Frontiers)

5. Contact the Veterinarian Early

Tell the veterinarian:

• Calf age

• Approximate weight

• Duration of diarrhoea

• Ability to stand

• Strength of suckle

• Eye recession

• Body temperature

• Milk intake

• Faecal appearance

• Previous treatment

• Number of other affected calves

6. Collect a Fresh Faecal Sample

Place fresh faeces in a clean, leakproof container and refrigerate it when instructed.

Do not delay life-saving treatment in a critically ill calf merely to obtain a sample.

When Are Oral Electrolytes Appropriate?

Oral electrolyte therapy is appropriate when the calf:

• Can stand

• Has a functional suckle or chewing reflex

• Can swallow normally

• Is not severely bloated

• Has less than approximately 8% dehydration

• Is still responsive

• Has not developed circulatory shock

A calf with any meaningful suckle or coordinated chewing action usually has enough gastrointestinal function to absorb oral fluid. A calf with no suckle, severe abdominal distension or recumbency needs veterinary assessment before force-feeding. (Calflyte Plus)

Start Treatment Early

Do not wait for obvious sunken eyes.

For neonatal calves, calf-specific oral electrolytes should generally begin at the first sign of watery diarrhoea because the speed of subsequent dehydration is difficult to predict. (Frontiers)

What Should a Calf Oral Electrolyte Contain?

Not every product labelled “electrolytes” provides adequate rehydration or alkalinisation.

Sodium

A suitable neonatal calf oral electrolyte generally contains approximately 90 to 130 mmol/L of sodium when mixed as directed.

Products containing too little sodium may not adequately expand extracellular fluid volume. Excessively concentrated sodium products may increase the risk of hypernatraemia, particularly if mixed incorrectly. (Frontiers)

Chloride

Chloride helps replace intestinal losses and maintain electrolyte balance. Its concentration must be considered alongside sodium and the alkalinising ingredients rather than judged in isolation.

Potassium

Potassium helps replace the total body deficit caused by diarrhoea and reduced milk intake.

The fact that blood potassium may be high in some acidotic calves does not mean the whole body contains too much potassium. (PubMed Central (PMC))

An Absorption Substrate

The formulation should contain at least one ingredient that facilitates sodium and water absorption, such as:

• Glucose

• Glycine

• Acetate

• Propionate

• Citrate

These transport pathways remain partly functional even when the intestinal lining has been damaged by infectious diarrhoea. (Frontiers)

An Alkalinising Agent

Watery calf diarrhoea generally requires a product containing bicarbonate or a metabolised bicarbonate precursor such as acetate, propionate or citrate.

The effective strong ion difference of the mixed oral solution should generally be approximately 40 to 80 mmol/L, with around 60 mmol/L considered a useful target for watery diarrhoea. Products without meaningful alkalinising capacity provide an inferior response in acidotic calves. (Frontiers)

Appropriate Energy Content

High-energy products can be helpful when the calf is consuming little milk, but excessive glucose may increase solution osmolality, slow abomasal emptying or leave unabsorbed carbohydrate available for intestinal fermentation.

A calf still consuming a normal milk ration generally does not need a very high glucose electrolyte solution. (Frontiers)

How Much Oral Fluid Does the Calf Need?

The initial fluid deficit can be estimated using:

Fluid deficit in litres = body weight in kilograms × dehydration fraction

For example, a 40 kg calf estimated to be 6% dehydrated has an initial fluid deficit of:

40 × 0.06 = 2.4 litres

That 2.4 litres replaces only the existing deficit. It does not include:

• Normal maintenance needs

• Continuing diarrhoeal losses

• Milk requirements

• Additional losses from fever or cold exposure

One small electrolyte feeding may therefore be nowhere near enough for a calf with persistent watery diarrhoea. The total daily fluid intake from milk, oral electrolyte and water may need to exceed 12% of body weight, depending on continuing losses. (Frontiers)

Follow the product label and the herd veterinarian’s protocol rather than doubling powder concentration to fit more electrolyte into a smaller volume.

Should Oral Electrolytes Be Given by Bottle or Tube?

Bottle Feeding Is Preferable When the Calf Suckles

Voluntary sucking:

• Confirms a functional suckle reflex

• Encourages closure of the oesophageal groove

• Reduces ruminal deposition

• Allows the calf to control swallowing

• Provides useful information about clinical recovery

Oesophageal Tube Feeding Requires Training

A properly placed oesophageal feeder can deliver oral electrolyte to a standing calf that will not drink enough voluntarily.

However, tubing is not harmless. Incorrect use can cause:

• Oesophageal injury

• Aspiration

• Ruminal fluid accumulation

• Bloat

• Ruminal acidosis

• Delayed recognition that the calf actually needs IV fluids

A recumbent calf with an absent suckle reflex should not receive repeated force-fed milk while waiting for improvement. A 2025 clinical trial found that intravenous bicarbonate-containing fluid was effective for correcting acid-base abnormalities, while force-feeding milk replacer through an ororuminal tube provided no clear benefit and was associated with poorer acid-base recovery. (PubMed)

Should Milk Be Continued During Calf Scours?

Yes, in most cases.

Milk provides:

• Energy

• Protein

• Fat

• Amino acids

• Substrates for intestinal repair

• Protection against excessive weight loss

Oral electrolytes replace water and minerals but usually do not provide enough nutrition to maintain a calf for several days.

Continuing milk feeding in calves with mild to moderate diarrhoea supports growth and intestinal recovery. Milk should generally not be withheld from a scouring calf that can swallow safely. (Journal of Dairy Science)

Feed Electrolytes Separately Unless the Label Says Otherwise

Many products are designed to be mixed with water and fed between milk meals.

A practical routine often places the electrolyte feeding approximately two to three hours away from milk. However, some products are specifically formulated for addition to milk.

Follow the exact label. Do not improvise by mixing ordinary electrolyte powder into milk replacer simply to save time. (K-State Extension)

When the Calf Will Not Drink Milk

A calf refusing milk is significantly more concerning than a calf with diarrhoea that continues nursing.

Assess:

• Suckle reflex

• Ability to stand

• Hydration

• Temperature

• Abdominal distension

• Respiratory signs

• Blood glucose and acid-base status where available

If the suckle reflex is absent, intravenous treatment should occur before attempting to force large quantities of milk.

When Are Intravenous Fluids Needed?

Intravenous fluid therapy is generally required when the calf:

• Is approximately 8% or more dehydrated

• Has eye recession of about 4 mm or more

• Cannot stand

• Has an absent or severely weakened suckle reflex

• Has cold extremities or poor circulation

• Is markedly acidotic

• Is severely depressed or comatose

• Cannot absorb oral fluid quickly enough

• Has failed oral treatment

• Has sepsis or shock

Other parenteral routes, including subcutaneous fluids, are inferior to the intravenous route for rapid resuscitation of a critically ill calf. (PubMed Central (PMC))

What Do Intravenous Fluids Need To Correct?

The veterinarian’s fluid plan must address several abnormalities simultaneously:

1. Restore circulating volume

2. Replace the free-water deficit

3. Correct metabolic acidosis

4. Correct sodium and chloride abnormalities

5. Manage potassium abnormalities safely

6. Correct hypoglycaemia when present

7. Restore kidney perfusion

8. Re-establish the suckle reflex

Blood gas analysis and serum electrolytes allow a more accurate plan, particularly in a recumbent or critically ill calf. (Frontiers)

Why Is Sodium Bicarbonate Important?

A balanced crystalloid such as lactated Ringer’s or normal saline may restore some circulating volume, but it may not provide enough alkalinisation for a severely acidotic diarrhoeic calf.

Intravenous sodium bicarbonate is the preferred rapid alkalinising treatment for moderate to severe metabolic acidosis in neonatal diarrhoeic calves. An isotonic bicarbonate solution provides both volume and immediate bicarbonate, while hypertonic bicarbonate may be used by veterinarians for faster correction followed by additional fluid. (ScienceDirect)

The amount required should be selected using blood-gas results or a validated clinical decision tree. Guessing at bicarbonate quantities can result in undercorrection, overcorrection, hypernatraemia or other complications.

How Quickly Should the Calf Respond?

With appropriate IV treatment, the calf’s mental status and circulation should begin improving within approximately 30 to 60 minutes.

Reassuring signs include:

• Stronger head carriage

• Improved awareness

• Warmer extremities

• Stronger suckle

• Ability to stand

• Urination

• Reduced eye recession

Failure to respond should prompt reassessment for:

• Inadequate fluid or bicarbonate dose

• Continuing severe losses

• Sepsis

• Hypoglycaemia

• D-lactataemia

• Pneumonia

• Meningitis

• Peritonitis

• A different primary diagnosis

(Frontiers)

Do All Scouring Calves Need Antibiotics?

No.

Diarrhoea by itself is not an indication for antimicrobial treatment.

A standing, alert calf that continues drinking milk, has a normal temperature and shows no evidence of systemic illness should usually receive fluids and close monitoring without routine antibiotics. (Illinois Experts)

When Are Antibiotics More Likely To Be Appropriate?

Veterinary antimicrobial treatment becomes more appropriate when the calf has:

• Fever or hypothermia

• Marked depression

• Complete milk refusal

• Weak or absent suckle

• Severe dehydration

• Blood or mucus in the faeces

• Pneumonia

• Navel infection

• Joint swelling

• Meningitis signs

• Suspected bacteraemia or sepsis

A 2026 evidence-based treatment algorithm reserved parenteral antimicrobials for calves meeting systemic-illness criteria and substantially reduced antimicrobial use without compromising health outcomes. (Journal of Dairy Science)

The drug, route, dose and withdrawal period must be selected by the herd veterinarian under current food-animal regulations. Do not use leftover antibiotics merely because the diarrhoea has changed colour.

What About Anti-Inflammatory Medication?

A veterinarian may use an appropriate non-steroidal anti-inflammatory drug to reduce pain, fever and inflammation.

The calf’s hydration, kidney perfusion and gastrointestinal status must be considered first. Giving an NSAID to a severely dehydrated, poorly perfused calf without correcting the fluid deficit may increase kidney and gastrointestinal risk.

Pain relief supports comfort and milk intake, but it does not replace rehydration or treatment of sepsis.

What Causes Calf Scours at Different Ages?

Age helps prioritise likely causes but does not establish a diagnosis.

Age pattern	Important causes and clues
First week	Enterotoxigenic E. coli, sepsis, feeding errors
Approximately 5 to 30 days	Cryptosporidium parvum, coronavirus, mixed infections
Second and third weeks	Rotavirus and coronavirus become important
Approximately 2 to 8 weeks	Salmonella, mixed infection and nutritional disease
Older than 3 to 4 weeks	Coccidiosis, giardiasis, nutritional or chronic enteric disease

Enterotoxigenic E. coli can produce peracute watery diarrhoea, shock and death during the first week. Cryptosporidium commonly causes profuse watery diarrhoea in calves approximately 5 to 30 days old and is zoonotic. Coronavirus, rotavirus and Salmonella may overlap substantially with these age ranges. (Cal DFA)

Enterotoxigenic E. coli

Typical features include:

• Very young calf

• Sudden profuse watery diarrhoea

• Rapid dehydration

• Weakness

• Low or normal temperature

• Shock

• Potential hyperkalaemia

ETEC disease must be distinguished from E. coli septicaemia, which may occur with or without obvious diarrhoea. (Cal DFA)

Cryptosporidium

Typical features include:

• Watery or mucoid diarrhoea

• Calf commonly 5 to 30 days old

• Dehydration

• Reduced appetite

• Several calves affected

• Significant environmental contamination

Cryptosporidium parvum can infect people. Gloves, handwashing, dedicated footwear and careful cleaning are essential. (Cal DFA)

Rotavirus and Coronavirus

These viruses damage the intestinal villi and cause maldigestion and malabsorption.

Affected calves may develop:

• Pale or watery diarrhoea

• Dehydration

• Depression

• Reduced appetite

• Mixed infection with other pathogens

Coronavirus may produce bloody diarrhoea in some cases and becomes more serious when combined with other agents. (Cal DFA)

Salmonella

Be particularly concerned when diarrhoea occurs with:

• Fever

• Fresh blood or mucus

• Severe depression

• Pneumonia

• Swollen joints

• Meningitis

• Multiple sick age groups

• Unexplained deaths

Salmonella Dublin can also establish carrier cattle and contribute to respiratory and systemic disease. (Cal DFA)

Nutritional Diarrhoea

Non-infectious diarrhoea may follow:

• Incorrect milk-replacer concentration

• Inconsistent mixing

• Overfeeding

• Abrupt milk changes

• Feeding at the wrong temperature

• Poor-quality water

• Dirty feeding equipment

• Irregular feeding intervals

Nutritional errors can also worsen infectious diarrhoea by increasing unabsorbed nutrients within the intestine.

How Do Veterinarians Diagnose an Outbreak?

Herd History

The veterinarian will review:

• Age at onset

• Number affected

• Mortality

• Colostrum management

• Calving distribution

• Dam vaccination

• Milk and milk-replacer preparation

• Housing and hygiene

• Recent weather

• Previous treatment

• Whether cows, calves or equipment move between groups

Physical Examination

Important findings include:

• Hydration

• Suckle reflex

• Ability to stand

• Temperature

• Heart and respiratory rates

• Navel and joint examination

• Lung sounds

• Abdominal distension

• Faecal appearance

Blood Testing

A critically ill calf may benefit from:

• Venous blood gas

• Bicarbonate or total carbon dioxide

• Sodium

• Chloride

• Potassium

• Glucose

• L-lactate

• Calcium

• Packed cell volume

• Total protein

These results allow fluid and bicarbonate treatment to be individualised.

Faecal Testing

Testing may include:

• Rotavirus PCR

• Coronavirus PCR

• Cryptosporidium testing

• Salmonella culture or PCR

• ETEC F5 testing in very young calves

• Coccidia testing in older calves

A positive faecal result still needs clinical interpretation because multiple organisms and asymptomatic shedding are common. (Cal DFA)

Necropsy

During severe outbreaks, a fresh, untreated or minimally treated calf may provide the most valuable diagnostic information.

Submit the carcass or tissues as soon as possible to minimise autolysis. Intestinal segments, intestinal contents, liver, spleen, lung, joints and other tissues may be needed depending on the clinical pattern. (Cal DFA)

How Often Should a Scouring Calf Be Rechecked?

Do not assess the calf once daily and assume the treatment is working.

During the first day, reassess at least every four to six hours:

• Can the calf stand?

• Has the suckle strengthened?

• Are the eyes less sunken?

• Are the ears and feet warmer?

• Is the calf drinking milk?

• Is urine being produced?

• Is the abdomen becoming distended?

• Is the mental status improving?

• Is the diarrhoea continuing at the same rate?

After IV treatment, improvement in circulation and attitude should usually begin within the first hour. Oral-fluid cases should show improving strength, hydration and appetite over several hours, even though the diarrhoea itself may continue. (Frontiers)

What Is the Prognosis?

More Favourable Features

The outlook is usually good when the calf:

• Remains standing

• Has a strong suckle

• Continues drinking milk

• Is treated early

• Is not hypothermic

• Responds promptly to oral fluids

• Has no evidence of sepsis

More Guarded Features

Concern increases when the calf:

• Cannot stand

• Has an absent suckle

• Is markedly hypothermic

• Has severe acidemia

• Is hypoglycaemic

• Has bacteraemia

• Has pneumonia, meningitis or joint infection

• Fails to respond to initial IV fluids

• Has been ill for several days before treatment

Profound acidemia, severe hypoglycaemia, recumbency and systemic disease are associated with poorer outcomes. (PubMed Central (PMC))

Common Calf Scours Mistakes

Waiting Until the Calf Is Down

Oral treatment works best before the calf loses the ability to stand or suck.

Treating the Faeces Instead of the Calf

The colour and consistency matter less than hydration, circulation, suckle, appetite and mental status.

Withholding Milk

Electrolytes replace fluid but cannot provide the nutrition of milk.

Giving Only One Electrolyte Feeding

A calf may have a deficit of several litres plus substantial continuing losses.

Doubling the Electrolyte Powder

Making the solution more concentrated can increase sodium and osmolality to dangerous levels. Mix it exactly as directed.

Mixing Electrolytes With Milk Without Checking the Label

Some products are designed for milk. Many are not.

Force-Feeding Milk to a Recumbent Calf

An absent suckle is an indication for IV treatment, not proof that a larger stomach-tube feeding is required.

Giving Antibiotics to Every Calf

Diarrhoea alone does not justify antimicrobial treatment.

Giving Anti-Inflammatories Before Correcting Dehydration

Poor kidney perfusion increases treatment risk.

Assuming Skin Tent Alone Is Accurate

Use standing ability, suckle strength, eye recession, temperature and mental status together.

Waiting Until Tomorrow To Recheck

A neonatal calf can deteriorate substantially over several hours.

How Can Calf Scours Be Prevented?

Ensure Adequate Colostrum Intake

Colostrum should be provided as soon as possible after birth, with adequate intake achieved within the first four hours.

Pay attention to:

• Quality

• Quantity

• Timing

• Cleanliness

• Calf vigour

• Suckle strength

Calves born after dystocia, cold exposure or assisted delivery are at increased risk of failing to consume enough colostrum without help. (Cal DFA)

Maintain Dam Nutrition

Poor maternal nutrition can contribute to:

• Weak labour

• Dystocia

• Reduced colostrum quality

• Reduced milk production

• Low-vigour calves

• Failed passive transfer

Review body condition and trace-mineral management with the herd veterinarian before calving. (Cal DFA)

Use Clean, Dry Calving Areas

Calves should be born into an environment with the lowest possible pathogen burden.

Remove heavily contaminated bedding and avoid calving repeatedly in the same progressively contaminated area.

Separate Calves by Age

Older calves shed pathogens into the environment and can infect younger, more vulnerable calves.

Systems such as the Sandhills calving approach move pregnant cows away from older cow-calf pairs at regular intervals, reducing exposure of newborn calves to pathogens accumulated earlier in the calving season. (Cal DFA)

Clean Feeding Equipment Properly

Buckets, bottles, nipples and stomach tubes should be:

• Cleaned after use

• Disinfected appropriately

• Allowed to dry

• Stored away from manure contamination

• Assigned to sick calves where practical

Provide Fresh Water and Starter Feed

Even milk-fed calves should have access to clean water.

Calf starter supports rumen development, but neither starter nor water replaces milk in a young scouring calf.

Vaccinate Strategically

Vaccines are available for selected scours pathogens, including rotavirus, coronavirus and enterotoxigenic E. coli.

The programme should be based on diagnosed herd risk, pregnancy timing and product-label instructions. Vaccination does not replace colostrum delivery, hygiene or calf-age separation. (Cal DFA)

Investigate Repeated Cases

If scours occurs every season, record:

• Age of each calf

• Dam parity

• Calving area

• Colostrum intake

• Pathogens identified

• Treatment

• Response

• Mortality

• Weather conditions

Patterns often reveal whether the biggest weakness is passive transfer, sanitation, calf grouping, nutrition or treatment timing.

Frequently Asked Questions

Should I keep feeding milk to a calf with scours?

Yes. Continue normal milk or nursing when the calf can swallow safely. Give oral electrolytes in addition to milk, usually at separate feedings unless the product label specifically directs mixing. (Frontiers)

When does a scouring calf need IV fluids?

IV fluids are generally required when the calf cannot stand, has an absent suckle reflex, has approximately 4 mm or greater eye recession, is about 8% or more dehydrated, feels cold or is severely depressed. (Frontiers)

Can I use a homemade electrolyte solution?

A carefully formulated emergency recipe may have a temporary role under veterinary direction, but commercial calf-specific products are safer and more consistent. Concentration errors can produce inadequate sodium, inadequate alkalinisation or dangerous hypernatraemia.

Does every scouring calf need antibiotics?

No. Antibiotics should generally be reserved for calves showing systemic illness or a high risk of bacteraemia. A bright calf that continues drinking milk and has no systemic signs usually needs fluid therapy rather than routine antimicrobial treatment. (Journal of Dairy Science)

How quickly should a calf improve after treatment?

A calf receiving effective IV treatment should begin showing improved circulation and mental status within approximately 30 to 60 minutes. A calf receiving oral electrolytes should be reassessed within four to six hours. Failure to improve or any deterioration requires veterinary reassessment. (Frontiers)

Final Thoughts

Calf scours is common, but treating every calf with the same electrolyte bottle and antibiotic is not a safe protocol.

The most important points are:

1. Assess the calf, not only the diarrhoea.

2. Ability to stand is a major treatment decision.

3. Suckle strength is one of the best indicators of severity.

4. Eye recession helps estimate dehydration.

5. Calves with less than approximately 8% dehydration may respond to oral fluids.

6. Calves with approximately 8% or greater dehydration usually need IV fluids.

7. Recumbency or an absent suckle is an emergency.

8. Severe metabolic acidosis usually requires sodium bicarbonate.

9. Continue milk whenever swallowing is safe.

10. Do not force-feed milk into a severely depressed calf.

11. Use a calf-specific oral electrolyte with adequate sodium and alkalinising capacity.

12. One electrolyte feeding may not replace the full fluid deficit.

13. Diarrhoea alone does not justify antibiotics.

14. Systemically ill calves may require parenteral antimicrobial treatment.

15. Reassess calves several times during the first day.

16. Colostrum, hygiene, calf-age separation and herd diagnostics prevent more deaths than chasing faecal colour with medication.

The most damaging mistake is waiting until the calf is flat, cold and no longer sucking. The treatment window begins when the faeces first become watery, while the calf is still strong enough to absorb oral fluid and continue drinking milk.

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ASK A VET™ can help producers organise calf age, weight, suckle strength, hydration findings, milk intake, faecal changes and treatment response while they work directly with their attending livestock veterinarian. A calf that cannot stand, has no suckle reflex, is severely cold, is struggling to breathe or is becoming minimally responsive still requires immediate hands-on veterinary treatment.