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

By Dr Duncan Houston

A pig does not have to stop eating completely or be unable to stand before something is wrong. The first clue may be a slower response at feeding, less interest in its surroundings or growth that quietly falls behind the rest of the pen.

For pigs raised for meat, these changes matter before the planned sale date. In breeding herds, an unsettled litter may reveal a sow’s problem before she looks obviously unwell.

The aim is to recognise a change from normal, investigate it and act at the right time. A pig still getting to the feeder has not necessarily passed its health check.

Quick Answer

Early signs of illness in pigs include reduced feed intake, slower growth, unusual lying behaviour, isolation, coughing, altered droppings, stiffness and skin changes. Check the individual pig alongside the rest of its group, including feed, drinkers, temperature and ventilation. Seek same-day veterinary advice for persistent appetite reduction or several signs together, and immediate help for breathing distress, collapse, seizures, severe weakness or a rapidly developing herd problem.

1. Feeding changes before the pig stops eating

Watch what each pig actually consumes. A pig may visit the feeder but take only a few mouthfuls, get pushed away or return repeatedly without eating normally.

Check the feeding system as well as the animal. Feed may be present in a hopper without reaching the trough properly. Look for blockages, spoiled feed, sudden ration changes and competition.

Test the drinkers physically. Their height, flow and accessibility must suit the pigs using them. A pipe connected to a water supply does not prove that water is reaching the pig. Queensland guidance recommends daily checks of feeding and watering systems and a plan for breakdowns.

If several pigs reduce intake together, investigate shared supplies and housing promptly. If one pig hangs back while the others eat normally, examine that individual. These patterns guide the investigation but do not identify the cause by themselves.

2. The pig becomes quieter or changes where it lies

Observe pigs before disturbing them. Notice an animal that interacts less, stays apart, remains lying when it would normally get up or repeatedly changes position as though uncomfortable.

Interpret the whole pen. Huddling and piling can indicate inadequate warmth, particularly in young pigs. Older pigs that spread apart, pant or lie in wet areas may be struggling with heat. Their preferred conditions depend on age, size, flooring and airflow.

A single withdrawn pig among otherwise comfortable animals deserves closer attention. So does a group whose behaviour suddenly changes.

Check conditions at pig level. A wall-mounted temperature reading cannot describe every draught, hot corner or poorly ventilated resting area. Watching the animals helps assess whether the housing is working for them.

3. Growth slows before the pig looks thin

Record weights at consistent stages and compare pigs of similar age, genetics and management.

A widening size difference can be useful information. However, being smaller than a pen mate is not, by itself, evidence of illness. Look for a change in the individual’s previous growth pattern.

Average daily gain is:

Weight gained ÷ days between weighings.

For example, gaining 10 kg over 14 days averages approximately 714 g per day. That is a calculation example, not a target for every pig.

Review feed intake, feed wastage and growth together. A deteriorating feed conversion figure warrants investigation, but cannot distinguish disease from feed quality or management problems.

Some respiratory diseases cause relatively mild outward signs while reducing growth and feed efficiency. An apparently quiet cough across a growing group can therefore have significance well beyond the noise.

4. Coughing or breathing changes appear at rest

Listen before entering the pen, then watch pigs while they are resting.

Look for repeated coughing, nasal discharge, faster breathing or increased abdominal effort. A recurring cough across a group needs investigation, even if most pigs still eat.

Pig respiratory disease often involves several infectious and environmental contributors. Ventilation, stocking conditions and mixing history belong in the assessment alongside the examination and laboratory results.

Open-mouth breathing with distress, pronounced abdominal effort or froth at the mouth or nose requires immediate veterinary attention. Severe pleuropneumonia is one possible cause, but these signs do not establish a diagnosis. Minimise handling while arranging help.

5. Droppings change, or the pig starts vomiting

Notice changes from the usual consistency and amount of faeces for that age and diet.

Loose faeces, dirty hindquarters or repeated straining can indicate intestinal disease. The possibilities differ between suckling piglets, newly weaned pigs and older animals. Several bacterial and viral diseases produce overlapping signs, so appearance alone rarely identifies the cause.

Young pigs with watery diarrhoea can lose fluid rapidly. Enterotoxigenic E. coli, for example, can cause severe diarrhoea, dehydration and deterioration in nursing and weanling pigs. A dull piglet that is drinking poorly needs prompt help.

Black, tar-like faeces are a different warning sign. They may contain digested blood. Gastric ulcers can cause pallor, weakness and poor growth, sometimes without diarrhoea. A pale, weak pig passing black faeces needs urgent assessment.

Repeated vomiting, obvious abdominal pain or rapid abdominal swelling also warrants urgent veterinary advice.

6. Movement becomes stiff or reluctant

Watch for shorter steps, difficulty rising, reduced weight-bearing or reluctance to reach feed and water.

Inspect the feet, legs and joints safely. Injuries, joint infections and developmental problems can all affect growing pigs. A pig that cannot bear weight or has a hot, swollen joint should be assessed promptly.

Lameness accompanied by fever, poor appetite or illness in several pigs raises concern about more than a simple foot injury. Erysipelas, for example, can cause reluctance to move and systemic illness.

Do not force a reluctant pig to walk repeatedly to see whether it “loosens up”. Record its movement and arrange an examination.

7. Skin, ears and tails provide extra clues

Check for new wounds, swelling, scratching, unusual redness or a change in skin colour.

Raised diamond-shaped skin lesions can occur with erysipelas, but they are not present in every case. Their absence does not rule the disease out.

Pay attention to tail and ear injuries. A newly tucked or limp tail can accompany discomfort, illness or social pressure, but tail position alone is not a diagnostic test.

Tail biting requires action on both the injured pig and the conditions contributing to the problem. Assess competition, health, feeding, ventilation and opportunities to explore. Unwell pigs may be less able to escape biting.

Protect injured animals from further damage and seek veterinary guidance for painful, deep or infected wounds.

8. Piglets need a lower threshold for intervention

A piglet beside the sow is not necessarily receiving enough milk.

Watch for effective suckling, activity and whether each piglet settles after feeding. Small or weak piglets can lose access to teats and become chilled. Early colostrum intake and appropriate warmth are especially important for vulnerable newborns.

A cold, weak piglet or one unable to suck needs immediate attention and a safe warming and feeding plan. Do not force milk into the mouth of a piglet that cannot swallow properly.

Iron deficiency is another important piglet problem. Piglets have limited iron reserves, grow rapidly and receive little iron from sow’s milk. Review the herd’s iron programme with your vet rather than waiting for obvious anaemia.

Marked pallor or weakness still needs examination. Do not assume every pale piglet simply needs another iron injection.

9. An unsettled litter can reveal an unwell sow

After farrowing, assess the sow and her litter together.

Piglets that repeatedly attempt to nurse, remain restless after feeding or fail to gain weight may be receiving inadequate milk. The sow may eat less, resist lying on her side or have a painful, swollen mammary gland.

Postpartum dysgalactia syndrome involves inadequate colostrum or milk production. Signs in the sow can be subtle, and the litter may provide the first clear indication.

Contact your vet promptly when a newly farrowed sow is off feed or her litter is not feeding effectively. A temperature reading helps, but temperature alone does not diagnose the problem because healthy sows can also have higher readings around farrowing.

How urgently should you act?

Rechecking later is appropriate only while the pig remains otherwise well. Do not wait for the next routine inspection when signs are worsening.

What will the vet investigate?

Age, production stage, recent movements and the number affected help narrow the possibilities.

Poor growth may reflect nutrition, competition, respiratory disease, intestinal disease or parasites. A faecal test can help assess some parasite infections, but treatment should match the findings and the herd’s risks.

Depending on the pattern, your vet may recommend examination, faecal testing, blood tests, respiratory sampling or feed and water analysis. An unexplained death may justify a veterinary post-mortem examination.

Bring records of weights, feed changes, weaning dates, recent introductions, treatments and deaths. Tell the vet whether the problem began in one pen or appeared across several groups.

When is this an emergency for the whole herd?

Rapidly spreading illness, unexpected deaths, unusual nervous signs or red-blue skin discolouration with systemic illness need urgent investigation. Serious infections such as African swine fever can overlap with more familiar diseases, so symptoms alone cannot confirm or exclude them.

Blisters or raw lesions around the snout, mouth or feet, especially with lameness, also need immediate assessment for possible emergency animal disease.

Stop unnecessary movement of pigs and potentially contaminated equipment. Call before transporting affected animals or opening a carcass.

In Australia, report suspected emergency animal disease to your veterinarian or the Emergency Animal Disease Hotline on 1800 675 888. You do not need to identify the disease before reporting unusual signs.

There is another pig-specific emergency to remember: prolonged water deprivation can cause dangerous sodium disturbances. If water has been unavailable and pigs develop incoordination, head pressing or seizures, call immediately. Rehydration needs veterinary direction because correcting the imbalance too quickly can worsen brain injury.

A practical plan when a pig seems unwell

1. Identify the pig and pen. Record when the change began and count how many animals are affected.

2. Observe before handling. Note feeding, posture, breathing, movement, faeces and interaction with pen mates.

3. Check equipment and conditions. Test drinkers, inspect feeders and check ventilation, cooling and warmth.

4. Provide suitable care. Use a comfortable hospital area when appropriate, with easy access to essentials and protection from bullying. For suspected emergency disease, seek instructions before moving pigs.

5. Contact your vet with the full picture. Include age, recent weights, treatments, feed changes and any temperature measured safely.

6. Set a reassessment time. Record treatment response and call sooner if the pig worsens.

For a heat-distressed pig, reduce handling, improve airflow and begin appropriate cooling while obtaining help. Avoid chilling nearby piglets while cooling adult pigs.

Record medicines carefully and follow the applicable meat withholding period and veterinary instructions. A planned sale date must not override treatment or residue requirements.

Common mistakes that delay recognition

• Assuming a pig at the feeder is eating normally. Watch actual intake and competition.

• Trusting a full water tank without testing drinkers. Problems can occur further along the system.

• Calling every cough dust or every scour a feed change. Persistent signs need investigation.

• Treating poor growth with extra feed or a drench alone. Find the limiting factor first.

• Waiting for the whole pen to look sick. One affected pig may be the first warning.

• Using leftover medication without a diagnosis. It may be unsuitable and complicate testing or withholding requirements.

Build early detection into daily management

Use a consistent daily observation routine, with closer checks around farrowing, weaning, transport, mixing, hot weather and equipment failures.

Feed a balanced ration suited to the production stage. Keep feed fresh, protect water supplies and provide adequate access for smaller or less dominant pigs.

Maintain comfortable flooring, dry resting areas and appropriate temperature and ventilation. Where suitable, manage groups together and clean, disinfect and dry accommodation between batches. Deal with sick groups after healthy groups and use dedicated equipment.

Provide safe, suitable materials for rooting, chewing and exploration. Enrichment supports normal behaviour and helps reduce redirected biting towards pen mates.

Work with your vet on vaccination, parasite control and the health status of incoming pigs. Protect the herd from contact with feral pigs and contaminated equipment.

In Australia, do not feed prohibited food waste containing meat or food that has contacted meat. This practice can introduce serious animal diseases and is banned.

For broader feeding, housing and growth planning, see how to optimise pork production.

Frequently asked questions

Can a pig be sick while still eating?

Yes. Reduced intake, slower growth or altered behaviour may appear before complete feed refusal. Assess the combination of signs and the change from that pig’s normal routine.

Does slower growth mean a pig has worms?

No. Nutrition, competition, respiratory disease and intestinal problems can also reduce growth. Examination and appropriate testing help avoid unnecessary treatment.

Is a coughing pig always an emergency?

A recurring cough needs investigation. Breathing difficulty, weakness, froth at the mouth or nose, or rapid spread through a group makes the situation urgent.

Will a pig catch up after being ill?

Some pigs recover well, but catch-up growth depends on the disease, its duration and any lasting damage. Track weight and comfort after treatment rather than assuming that returning to the feeder means full recovery.

A small change becomes useful when someone records it and follows it up. Knowing which pig is eating less, moving differently or falling behind gives your vet a much better starting point.

ASK A VET™ helps you understand the changes worth tracking and prepare useful questions for your herd veterinarian. If a pig is deteriorating rapidly or several animals become unwell together, seek hands-on veterinary help immediately.