Early Signs of Illness in Racehorses: What to Notice Before They Look Sick

By Dr Duncan Houston

The horse still comes to the stable door. It still eats some breakfast. It still completes its work. Yet the groom says it is quieter, the rider says it feels different, and yesterday’s feed took longer to finish.

That is worth investigating. In racehorses, early illness and pain can appear as small changes in routine, comfort and recovery before obvious lameness, fever or a major performance decline develops.

The aim is to recognise a change early enough to make a sensible decision about examination, treatment and training. Waiting for a horse to look properly sick can mean missing useful warning signs.

Quick Answer

Early signs of illness in racehorses include eating more slowly, leaving feed, becoming unusually quiet or irritable, altered manure, a shorter stride, reduced willingness to work and slower recovery after exercise. Compare the horse with its own normal behaviour and consider several observations together, including resting temperature and recent travel or training changes. Stop strenuous work and seek veterinary advice when a new health concern appears; severe pain, breathing difficulty, collapse or sudden severe lameness require immediate veterinary attention.

1. The horse eats, but its feeding pattern changes

A horse does not need to refuse an entire meal before appetite becomes a concern.

Watch for a horse that starts eating enthusiastically but stops early, repeatedly returns to an unfinished feed or begins leaving forage it usually consumes. Record what remains instead of simply topping up the manger and losing track.

How the horse chews matters too. Dropping balls of partly chewed hay, spilling grain, chewing slowly or losing condition can indicate dental disease. A horse that appears fussy may actually find eating uncomfortable.

Poor appetite can also occur with gastric ulcers, but it does not identify the cause. Mouth discomfort, intestinal problems and other illnesses need consideration.

Check feed quality and water access, then assess the horse. A different batch of hay may explain a preference change, but it should not become the automatic explanation for persistent poor appetite.

2. Its usual personality changes

Some horses become quieter. Others become irritable when groomed, saddled or asked to work. What matters is a change from the horse’s established behaviour.

Useful observations include being less interested in its surroundings, repeatedly moving away during handling or becoming reluctant to perform a familiar task. Record the circumstances. “Sensitive when brushing the right side of the back” gives the vet more information than “in a bad mood”.

Behavioural changes can accompany pain, but no single behaviour identifies a disease.

For example, girthiness, poor appetite and reduced performance are sometimes associated with gastric ulcers. They also occur for other reasons. Gastroscopy is needed to confirm gastric ulcer disease; a grumpy response to the girth is not a diagnosis.

3. Manure and drinking habits become different

Daily stable cleaning provides a useful health check. Notice whether manure output is lower than usual, droppings are smaller or drier, or faeces have become unusually loose.

Reduced appetite, flank watching, pawing and repeatedly lying down can be early signs of abdominal discomfort. Some horses with colic initially look quiet rather than dramatically painful. Call your vet promptly when colic is suspected.

Check water consumption where practical, particularly after travel or during hot weather. Test automatic drinkers rather than assuming they work because the bowl contains water.

Reduced drinking can contribute to dehydration, poor performance and impaction colic. Always provide plain, clean water, including when electrolytes are offered under an appropriate feeding plan.

A wetter stable or a change in drinking can also be worth reporting. Diet, weather and workload affect water needs, so interpret changes in context.

4. Resting observations drift away from normal

Knowing the horse’s healthy baseline makes a small change easier to recognise.

Ask your vet to show staff how to measure temperature, pulse and breathing safely. Record these when the horse is calm and resting, not immediately after exercise or an exciting trip around the yard.

A repeated rise in resting pulse or breathing rate deserves attention, particularly alongside poor appetite, discomfort or dullness. One measurement cannot tell you whether the cause is pain, heat, excitement or disease.

A resting temperature around 38.6°C or higher warrants prompt veterinary advice, particularly after travel or contact with other horses. Illness can still be present below that temperature.

If fever occurs with coughing, nasal discharge or diarrhoea, separate the horse pending advice and use dedicated equipment. Handle healthy horses before potentially infectious horses.

5. The rider notices a change before obvious lameness appears

Early discomfort may be felt under saddle before it becomes obvious from the ground.

Take reports seriously when a horse:

• Feels shorter or less even in its stride.

• Becomes reluctant to accelerate or maintain its usual rhythm.

• Repeatedly struggles with a familiar turn or movement.

• Feels unusually stiff during or after work.

• Develops a new response to saddling or mounting.

Check for new limb swelling, heat or tenderness, and share those findings with the vet. Their absence does not establish that the horse is sound.

Research into racehorse injuries shows that pre-existing skeletal damage can contribute to catastrophic fractures. A change in movement should prompt assessment before further fast work. Sending the horse out for another gallop to see whether it improves is not a safe diagnostic test.

Not every serious injury gives a recognisable warning. Good observation supports veterinary assessment but cannot guarantee prevention.

6. Breathing problems appear as reduced performance

A horse with a respiratory problem may look comfortable in the stable and struggle only during demanding exercise.

Mild to moderate equine asthma can cause reduced exercise tolerance with little change in resting breathing. Coughing may be occasional rather than constant. Normal routine blood results do not exclude airway inflammation.

Report a recurring cough, new breathing noise, nasal discharge or an unexplained change in exercise tolerance. Note whether it happens at rest, when first moving off, during faster work or afterwards.

Exercise-induced pulmonary haemorrhage, often called EIPH, is another consideration in racehorses. Bleeding occurs within the lungs, and most affected horses do not have visible blood at the nostrils. Diagnosis requires veterinary investigation, often involving endoscopy.

Any nosebleed warrants prompt advice because other conditions can also cause it. Heavy or ongoing bleeding is an emergency.

7. Recovery becomes slower or less comfortable

Recovery should be interpreted against the workload, weather, fitness and horse’s previous response to similar exercise.

A useful record includes the work completed, environmental conditions, breathing during recovery and how quickly the horse returns to its usual demeanour. A hard effort on a humid day cannot be compared directly with light work in cool weather.

Persistent distress, weakness or laboured breathing should not be dismissed as ordinary tiredness.

Heat illness requires exercise to stop and cooling to begin promptly. Continuous application of cool or cold water is effective. Scraping between applications is unnecessary and interrupts cooling. Provide shade and airflow when possible, and contact your vet if the horse is distressed or recovering abnormally.

8. Muscle soreness is unusually marked

Painful, firm hindquarter or back muscles, trembling, excessive sweating and reluctance to move during or after exercise can indicate tying-up, also called exertional rhabdomyolysis.

Some episodes are mild; others cause extensive muscle damage and kidney complications. Dark urine is concerning, but you should not wait for it before seeking help.

Stop exercise, minimise movement and call your vet immediately if tying-up is suspected. Do not try to walk it off.

Muscle enzyme tests help assess the damage. The appropriate return to exercise depends on the type of muscle disorder and the individual horse’s response, so a fixed “few days off” rule is unreliable.

What should you record each day?

Keep the system simple enough that everyone actually uses it.

When	Useful observations
Before feeding and exercise	Alertness, posture, overnight feed remaining, manure, resting breathing and temperature under the stable’s monitoring plan
During grooming and preparation	New sensitivity, swelling, wounds, reluctance to move or changed responses to tack
During work	Rider’s observations, stride, willingness, cough, breathing noise and any reason the session was changed
After work	Recovery in relation to workload and weather, sweating, comfort, drinking and appetite
Later that day	Whether earlier changes resolved, persisted or became more pronounced

Record actual findings where possible. “Left approximately half the evening feed” is more useful than “appetite okay”.

The groom’s observation and the rider’s observation may each seem minor until someone puts them together. Make sure concerns reach the person deciding the next day’s work.

How worried should you be?

Level of concern	Examples	Action
Needs a closer check	One mild change with normal appetite, movement, breathing and demeanour	Check the horse and its surroundings now. Reassess later the same day and before exercise
Needs prompt veterinary advice	Persistent appetite change, new gait abnormality, repeated poor performance, recurring cough or unexplained slow recovery	Stop strenuous work and contact your vet that day
Possible infectious illness	Fever, particularly with respiratory signs or diarrhoea	Separate the horse and seek prompt veterinary advice
Emergency	Suspected colic, severe breathing difficulty, collapse, suspected tying-up or sudden severe lameness	Call a vet immediately for assessment and instructions

Escalate sooner if several changes occur together or the horse is deteriorating. A horse with pain or an altered gait should not continue its training programme while someone waits to see whether another sign appears.

What might be causing the changes?

The same outward sign can come from several problems. Reduced appetite may direct attention towards the teeth, stomach or intestines. Altered stride raises concern about the feet, limbs, back or muscles. A cough or poor exercise tolerance brings the respiratory tract into focus.

Training load, feed, tack, surfaces and weather also need review. These factors can contribute to a problem without explaining every sign.

The vet uses the history and examination to decide which tests are appropriate. Depending on the findings, investigation may include lameness assessment and imaging, blood tests, airway endoscopy or sampling, and gastroscopy.

There is no single “fitness blood test” that rules out every important condition. For example, equine asthma may require airway investigation even when routine blood results are normal.

When is this an emergency?

Call an emergency veterinarian immediately for:

• Severe or persistent abdominal pain, repeated rolling or rapid deterioration.

• Marked breathing difficulty, collapse or loss of coordination.

• Sudden severe lameness or inability to bear weight.

• Painful muscle stiffness with sweating or reluctance to move.

• Overheating with distress, weakness or abnormal behaviour.

• Heavy or ongoing bleeding.

For suspected fracture, keep the horse as still as safely possible and obtain veterinary instructions before moving or loading it.

For suspected colic, ask the vet about feed and movement. Walking may be appropriate if the horse is comfortable and safe to handle, but do not force it to walk to exhaustion. Quiet lying down is not automatically a reason to keep dragging it around the yard. Pain medication can mask important signs, so give it only under veterinary direction.

For heat illness, start cooling while help is being arranged. Do not withhold drinking water simply because the horse is hot.

A practical plan when your horse seems “not quite right”

1. Pause strenuous work. Tell the trainer and relevant staff exactly what has changed.

2. Observe quietly. Look at posture, breathing, appetite and comfort before handling.

3. Collect useful information. Record the timing, safe resting measurements, recent workload, transport, feed changes and medications.

4. Check the basics. Confirm water supply, feed quality, ventilation and whether other horses are affected.

5. Contact your vet according to the signs. Do not wait until tomorrow for colic, marked pain, fever with illness or abnormal breathing.

6. Agree on follow-up and return to work. Improvement after treatment does not automatically establish that fast work is safe.

A short video may help communicate what happened, but never exercise a painful horse or provoke breathing difficulty to obtain one.

Common mistakes that delay recognition

• Calling a horse lazy when its behaviour changes. Investigate comfort and health before assuming motivation is the problem.

• Waiting for complete feed refusal. Changes in eating pattern can be useful earlier clues.

• Training harder because performance has dropped. First establish whether the horse is healthy enough for the planned work.

• Treating every sign as ulcers. Behaviour and appetite alone cannot confirm the diagnosis.

• Relying on one reassuring result. Normal temperature, bloodwork or appetite does not exclude every disease.

• Masking signs before assessment. Discuss medication with the treating vet and keep accurate treatment records.

How to make early recognition part of normal management

Build a veterinary health programme around the individual horse and the stable’s travel, training and housing arrangements. Include appropriate vaccination, parasite control, nutrition and procedures for new arrivals or returning travellers.

Maintain dental and hoof care, reliable water access and a suitable forage-based ration. Introduce training and dietary changes gradually, with recovery appropriate to the horse’s condition.

Reduce dust through bedding, forage and ventilation choices. Environmental management is central to controlling equine asthma.

Allow appropriate rest, safe social contact, enrichment and turnout where suitable for the horse’s medical and training needs. Introduce unfamiliar environments gradually where practical.

For the broader management picture, read how to optimise racehorse performance.

Frequently asked questions

Can a racehorse be sick but still eat and train?

Yes. Some illnesses and painful conditions initially cause subtle changes rather than complete loss of appetite or obvious inability to exercise. Completing a session does not prove the horse is healthy.

Is a small drop in performance always a medical problem?

No. Workload, track conditions, weather and many other factors influence performance. A new or repeated decline deserves closer attention, especially when appetite, movement, behaviour or recovery also changes.

Should I wait for a fever before calling the vet?

No. Painful injuries, muscle disorders and some respiratory problems may occur without fever. Base the decision on the whole picture and the urgency of the signs.

Can early detection prevent every serious injury?

No. Some problems remain difficult to detect, and some emergencies develop quickly. Careful observation and appropriate veterinary investigation improve decision-making without guaranteeing that every injury can be prevented.

You do not need to identify the diagnosis before reporting a change. A clear observation, shared promptly, can be enough to start a useful investigation and protect the horse from avoidable further strain.

ASK A VET™ supports a better understanding of your horse’s health and the changes worth discussing with your treating veterinarian. When your racehorse seems different, record what you notice and seek advice early. Emergency signs need immediate hands-on veterinary care.