Pigs are hardy omnivores, but several common foods, plants, and feed contaminants can sicken or kill them. Some of the most dangerous items are ones you might not suspect: green potatoes, fruit pits, moldy grain, and even too much salt when water runs low. Whether you raise pigs on pasture, keep a pet pig, or supplement feed with kitchen scraps, knowing what to avoid can prevent serious losses.
Green Potatoes and Nightshade Plants
Green potatoes, potato sprouts, and the leaves and stems of tomato and potato plants all belong to the nightshade family. They contain glycoalkaloids, most notably solanine, which damage the digestive tract and nervous system. Historical outbreaks in Poland involving 180 pigs resulted in a 64% mortality rate. The lesson is straightforward: never feed pigs potatoes that have turned green or sprouted, and keep them away from nightshade foliage in gardens or compost piles.
Other nightshade species grow wild in pastures and along fence lines. These weedy plants produce the same class of toxins and are dangerous to pigs, cattle, sheep, and horses alike.
Dangerous Pasture Plants
Several common weeds can poison pigs that graze or root through pastures and hedgerows.
- Poison hemlock: Even a small amount is lethal. It contains piperidine alkaloids that cause respiratory failure. Pregnant sows that eat it between days 30 and 60 of gestation can deliver piglets with skeletal deformities or cleft palate.
- Cocklebur: Most dangerous in the seedling stage, when the two-leaf sprouts emerge in spring. Pigs rooting in freshly tilled or flooded ground are at highest risk.
- Jimsonweed (thornapple): Toxic to all livestock and humans. The seeds and leaves contain tropane alkaloids that cause rapid heart rate, disorientation, and seizures.
- Yew: All parts of the yew tree, including clippings thrown over a fence, contain the alkaloid taxine. Ingestion is often fatal before symptoms are even noticed.
Pigs raised on pasture should have their grazing areas inspected regularly, especially in spring when seedlings emerge and in fall when berries drop. If you can’t identify a plant, remove it or fence pigs away from it.
Fruit Pits and Seeds
The pits of cherries, peaches, apricots, and plums, along with apple seeds and bitter almonds, contain cyanogenic glycosides. When chewed and digested, these compounds release hydrogen cyanide. In pigs, cyanide doses as low as 1.2 mg per kilogram of body weight have caused thyroid changes and behavioral abnormalities in studies. A handful of crushed pits won’t necessarily kill a full-grown pig, but the risk scales quickly with smaller animals or larger quantities. Remove pits and cores before offering fruit as a treat.
Onions and Garlic
Onions and garlic, whether raw, cooked, or dried, can trigger a type of anemia in pigs where red blood cells break down faster than the body can replace them. Affected animals become weak, pale, and may collapse. Pigs are more susceptible than sheep or goats. Garlic is three to five times more potent than onion, so even small amounts in kitchen scraps add up. The safest approach is to keep all allium family foods out of pig feed entirely.
Chocolate and Caffeine
Chocolate contains theobromine and caffeine, both of which are toxic to pigs. Theobromine is present at three to ten times the concentration of caffeine in chocolate, and together they can cause dangerous heart rhythm problems and nervous system dysfunction. Deaths have been documented in livestock fed cocoa byproducts and in animals that consumed cocoa bean hull mulch. Dark chocolate and baking chocolate carry the highest risk because of their elevated theobromine levels. Keep all chocolate products, coffee grounds, and cocoa-based mulch away from pigs.
Salt Poisoning and Water Deprivation
Salt itself isn’t the whole problem. Pigs can tolerate fairly salty feed as long as they have constant access to fresh water. The real danger comes when water is restricted or unavailable, even briefly. When a pig takes in too much sodium without enough water to flush it, sodium levels in the blood spike. Water gets pulled out of brain cells, causing them to shrink, which can tear blood vessels and cause hemorrhaging inside the skull.
What makes salt poisoning especially treacherous is the recovery phase. Once a dehydrated pig finally gets water, the swollen brain cells can cause fatal cerebral edema. Reintroducing water must be done gradually. Drinking water for pigs should contain less than 0.5% total salt. The simplest prevention is never letting waterers run dry, especially in hot weather or when feeding salty food scraps.
Moldy Feed and Mycotoxins
Pigs are particularly sensitive to mycotoxins, the invisible toxic compounds produced by molds that grow on stored grain, especially corn. The three most damaging mycotoxins in pig production are aflatoxins, deoxynivalenol (often called “vomitoxin”), and fumonisins. All three are common worldwide and frequently contaminate corn, which is the main ingredient in most pig diets.
Aflatoxins attack the liver, suppress the immune system, and slow growth. Even low-level chronic exposure damages liver function and can eventually promote tumor development. Deoxynivalenol reduces feed intake by roughly 11% and daily weight gain by about 9% at contamination levels of just 1 mg per kilogram of feed. Fumonisins cause lung and liver damage. Together, these toxins weaken intestinal barriers, make pigs more vulnerable to infections, and cut into growth performance.
Preventing mycotoxin problems starts with proper grain storage: keep feed dry, use it before it ages, and inspect it for visible mold, musty smell, or discoloration. Any feed that looks or smells off should be discarded.
Kitchen Scraps and Meat Waste
Feeding pigs table scraps is a time-honored practice, but it comes with real legal and health boundaries. Under federal law (the Swine Health Protection Act) and most state regulations, food waste that contains or has contacted meat, poultry, or fish is classified as “garbage” and carries strict rules. The concern is disease transmission: feeding raw or improperly handled meat waste to pigs has historically spread diseases like foot-and-mouth disease, classical swine fever, and trichinosis.
In many states, feeding meat-containing waste requires a license, and the waste must be heat-treated before it reaches your pigs. Vegetable scraps, fruit (without pits), stale bread, and other plant-based leftovers are generally safe and legal, provided they haven’t been mixed with meat products. If you source food waste from restaurants or grocery stores rather than your own kitchen, check your state’s specific licensing requirements before you start.
Signs of Poisoning in Pigs
Recognizing toxicity early gives you the best chance of saving an animal. The first signs are usually sudden vomiting or diarrhea, sometimes with blood. Excessive drooling, refusal to eat, and abrupt lethargy or weakness are also common early warnings. More serious poisoning produces tremors, seizures, labored breathing, or a wobbly, uncoordinated gait. Pale or bluish gums suggest either anemia or oxygen deprivation, both of which signal a veterinary emergency.
If you suspect poisoning, remove the pig from the source immediately and note what it may have eaten, how much, and when. Having this information ready when you contact a veterinarian makes diagnosis and treatment significantly faster.