A pig that stops eating is almost always telling you something is wrong. Pigs are highly food-motivated animals, so a genuine refusal to eat, even for a single day, signals a problem that needs attention. The cause could be as simple as a hot day or spoiled feed, or as serious as an infection running a high fever. Working through the most likely causes systematically will help you figure out what’s going on and how urgently your pig needs help.
Check for Fever First
The fastest way to narrow down the problem is to take your pig’s rectal temperature. A healthy pig’s normal range is 101.6 to 103.6°F (38.7 to 39.8°C). Anything above that range suggests an infection or inflammatory process, and a reading over 105°F points to a serious illness that needs veterinary attention quickly.
Fever is the single most common reason pigs go off feed suddenly. Bacterial infections like erysipelas, respiratory infections like pasteurellosis, and gut infections like salmonellosis all cause fevers of 104 to 108°F alongside appetite loss. A pig with a fever will often look dull, shiver, have raised hair along its body, and be reluctant to stand. If you see a combination of fever plus any of those signs, you’re dealing with a sick pig rather than a picky one.
Heat Stress Suppresses Appetite
Pigs don’t sweat effectively, which makes them extremely sensitive to high temperatures. As the ambient temperature climbs from about 66°F to 84°F (19 to 29°C), finishing pigs progressively eat smaller meals and spend less time at the feeder. Under cyclic heat stress, where daytime temperatures spike and nightfall brings some relief, feed intake drops by roughly 7%. Under constant heat at 95°F (35°C), pigs can cut their intake by half.
If your pig has stopped eating on a hot day, this is the most likely explanation. Provide shade, fans, misters, or a mud wallow. Pigs that are simply overheated will resume eating once they cool down, typically in the evening. If your pig still won’t eat after the temperature drops, heat stress alone probably isn’t the answer.
Contaminated or Spoiled Feed
Pigs have a surprisingly sharp ability to detect mold toxins in grain and will refuse feed that smells or tastes off. Mycotoxins produced by common grain molds are a well-documented cause of feed refusal. One toxin in particular, deoxynivalenol (commonly called vomitoxin), triggers feed refusal at very low levels. Concentrations above 1 part per million can reduce intake and slow growth. Above 5 parts per million, pigs will refuse the feed entirely.
Other mycotoxins act as immune suppressors and cause vomiting, weight loss, and frequent defecation even at levels below 1 ppm. If you recently opened a new bag or batch of feed, or if feed has been stored in a humid area, try offering a completely different, fresh feed source. A pig that eagerly eats the new feed but ignores the old one is telling you the problem is in the bag, not in the pig.
Gastric Ulcers
Stomach ulcers are surprisingly common in pigs and are a frequent cause of gradual appetite loss. The hallmark signs are pale skin, loss of appetite, weight loss, and dark, tarry feces. In a study of symptomatic pigs, nearly 57% showed pale skin and about 34% had bloody or black tarry stool. Some pigs with severe ulcers die suddenly with no prior warning signs.
Ulcers develop more readily in pigs fed finely ground feed, pigs under chronic stress, and pigs with irregular feeding schedules. A pig with ulcers gains roughly 50 to 75 grams less per day than a healthy pig during the growing phase. If your pig has been eating less and less over days or weeks, especially combined with pale gums or dark stool, ulcers are a strong possibility and worth discussing with a vet.
Water Problems and Salt Toxicity
A pig that can’t access enough fresh water will stop eating. This sounds obvious, but it’s one of the most commonly overlooked causes. Nipple waterers freeze in winter, get clogged with debris, or malfunction without the owner noticing. Pigs on a normal diet that lose access to water, even briefly, risk developing salt toxicity because the sodium in their regular feed builds up without enough water to flush it.
Severely affected pigs may become blind, deaf, and completely unresponsive to their surroundings. They won’t eat, drink, or react to you at all. Earlier signs include weakness, wobbliness, muscle tremors, and wandering or circling. If your pig stopped eating and you have any doubt about whether its water supply has been working reliably, check the waterer immediately. Restoring water access needs to be done gradually, because drinking a large volume too quickly after deprivation can worsen brain swelling.
Internal Parasites
A heavy worm burden causes a slow, grinding loss of appetite rather than a sudden refusal. The swine whipworm is one of the most problematic parasites for appetite. Infections cause diarrhea, anorexia, anemia, poor growth, and in severe cases, emaciation. The severity depends on how many parasites the pig is carrying and whether it also has a bacterial gut infection at the same time, which is common because parasites damage the intestinal lining and let bacteria in.
If your pig has had inconsistent or no deworming, has access to dirt or pasture, and has been gradually eating less with loose stool and a rough coat, parasites belong high on your list of suspects. A fecal exam from your vet can confirm the diagnosis.
Social Stress and Bullying
If you keep more than one pig, social dynamics can suppress appetite in the lower-ranking animal. Subordinate pigs that are bullied away from feeders or harassed by dominant pen-mates can develop a pattern of undereating sometimes called “wasting pig syndrome” or “thin sow syndrome.” The stress doesn’t just make them avoid the feeder out of fear. It can trigger hormonal changes in the brain’s hunger-regulating systems, physically suppressing the drive to eat in a way that mirrors stress-induced appetite loss in other mammals.
Recent changes are the usual trigger: introducing a new pig, moving pigs to a new pen, or separating a young pig from its mother too early. If you suspect bullying, watch your pigs at feeding time. Providing a second feeding station or separating pigs during meals often solves the problem quickly.
Red Flags That Need Immediate Attention
Some combinations of signs alongside appetite loss suggest an emergency:
- Blue or purple ears, snout, or belly skin. This can indicate an acute viral infection, bacterial blood poisoning, or a toxic state. Conditions like flu, acute pneumonia, or reproductive infections can cause this discoloration.
- Vomiting. Occasional vomiting can point to gastric ulcers, but repeated vomiting may signal a serious gut infection.
- Blood or mucus in stool. This suggests dysentery, salmonella, gastric ulceration, or another significant intestinal disease.
- Excessive drooling. Unusual salivation can indicate vesicular diseases, some of which are reportable and highly contagious.
- Complete unresponsiveness. A pig that won’t rise, won’t react to you, and shows no interest in its surroundings needs a vet the same day.
A single missed meal in an otherwise bright, active pig on a hot afternoon is not an emergency. A pig that hasn’t eaten in 24 hours, looks dull, and shows any of the signs above is a different situation entirely.
How to Coax a Recovering Pig to Eat
Once you’ve identified and started addressing the underlying problem, getting calories and fluids back into your pig matters. Offer small amounts of high-moisture, palatable foods. Many pig owners have success with watermelon, canned pumpkin (plain, not pie filling), applesauce, or soaked feed made into a warm mash.
For hydration, you can make a simple electrolyte solution at home: mix one liter of water with 20 grams of glucose (about 4 teaspoons of sugar), 3.5 grams of salt (about half a teaspoon), and 2.5 grams of baking soda (about half a teaspoon). Offer this alongside plain water so the pig can choose. Don’t force-feed a pig that is actively vomiting or completely non-responsive, as aspiration into the lungs is a real risk. A pig that won’t take anything voluntarily for more than a day likely needs veterinary support with fluids.