Blood in a Pig’s Stool: Causes, Severity & When It’s an Emergency

Blood in stool is a symptom, not a diagnosis. In pigs, one of the most important causes is large-intestinal inflammation. Merck notes that swine dysentery causes a mucohemorrhagic diarrhea with mucus and frank blood, especially in growing pigs. Intestinal salmonellosis can also cause diarrhea with mucus, necrotic debris, and sometimes blood, and affected pigs are often feverish and off feed.

Another major cause is Lawsonia intracellularis infection, also called porcine proliferative enteropathy or ileitis. This condition can range from loose, reddish-brown stool to a hemorrhagic form with weakness, pallor, and black or tarry feces. In some pigs, gastric ulcers cause dark stool from digested blood rather than bright red streaks. Merck describes dark feces and anemia as warning signs of gastric ulceration.

Parasites can also contribute, especially in pigs with outdoor access or heavy environmental exposure. Whipworms in pigs may cause diarrhea, poor growth, dehydration, and sometimes bloody stool. In young piglets, coccidiosis is more often linked with diarrhea than obvious bleeding, but it still belongs on the list when age and housing fit.

Less common but serious possibilities include rectal trauma, foreign material, severe constipation with straining, toxin exposure, clotting problems, or sudden internal intestinal bleeding. If more than one pig is affected, your vet may think first about infectious disease and herd-level management, not only the individual pig.

See your vet immediately if your pig has more than a small streak of blood, repeated bloody diarrhea, black or tarry stool, weakness, pale skin, collapse, belly pain, vomiting, fever, or a sudden drop in appetite. These signs can go along with dehydration, anemia, severe colitis, or internal bleeding. Young piglets and small miniature pigs have less reserve and can become unstable faster.

A same-day visit is also wise if the stool has mucus plus blood, if your pig is straining, if there is weight loss, or if another pig in the home or group has diarrhea. Infectious causes can spread through fecal contamination, feed, water, bedding, or shared surfaces. Until your vet advises otherwise, isolate affected pigs from healthy ones as much as practical and use careful hand hygiene.

Home monitoring is only reasonable when there is one brief episode of a tiny amount of bright red blood, your pig is otherwise bright, eating, drinking, and acting normally, and the stool quickly returns to normal. Even then, call your vet for guidance because pigs can hide illness well.

If you are unsure whether the stool is red from blood or from food, take a photo and save a fresh sample. Beets, some red treats, and certain medications can change stool color, but black, tarry stool or repeated red blood should always be treated as potentially urgent until your vet says otherwise.

Your vet will start with a physical exam, hydration check, temperature, heart rate, gum or skin color assessment, and questions about diet, recent feed changes, access to toxins, deworming history, housing, and whether other pigs are sick. A fresh fecal sample is very helpful. In pigs with diarrhea and blood, testing may include fecal flotation or parasite testing, fecal PCR panels, bacterial culture, and bloodwork to look for dehydration, inflammation, anemia, or protein loss.

If your vet suspects infectious enteritis, they may recommend testing for conditions such as salmonellosis, swine dysentery, or Lawsonia. Merck notes that confirmation of salmonellosis often involves culture and serotyping, while Lawsonia is commonly confirmed with PCR or tissue testing. In some cases, your vet may also suggest ultrasound, radiographs, or referral if there is concern for obstruction, severe ulcer disease, or ongoing internal bleeding.

Treatment depends on the cause and severity. Options may include fluids, electrolyte support, anti-ulcer medication, carefully selected antimicrobials when indicated, parasite treatment, diet adjustment, pain control chosen by your vet, and hospitalization for pigs that are weak, pale, or dehydrated. If there is concern for a contagious disease, your vet may also discuss sanitation, isolation, and protecting other pigs in the household or group.

Because some pig intestinal diseases can affect groups and some organisms can pose a zoonotic risk, your vet may recommend gloves, dedicated boots, separate cleaning tools, and stricter manure handling while test results are pending.

Home care should only be done with your vet’s guidance and only if your pig is stable. Keep your pig in a clean, dry, low-stress area with easy access to fresh water. If your vet recommends an electrolyte solution or temporary diet adjustment, follow those instructions closely. Watch stool frequency, appetite, drinking, energy level, and whether the blood is bright red or black and tarry.

Clean manure promptly and wash hands after handling your pig, bedding, bowls, or stool. If you have more than one pig, use separate boots, tools, or cleaning supplies if possible until your vet rules out a contagious cause. This matters because some infectious diarrheal diseases spread efficiently through fecal contamination.

Do not start over-the-counter human medicines on your own. Some can be unsafe, can hide worsening disease, or can interfere with diagnosis. Also avoid making abrupt feed changes unless your vet recommends them, because sudden diet shifts can make GI upset worse.

Call your vet again right away if the bleeding increases, your pig stops eating, seems weak, becomes pale, develops a swollen or painful belly, or passes black stool. Those changes can mean the situation is no longer safe to monitor at home.