When people see a pig vomit, their first reaction is often, “It must have eaten something bad” or “There’s something wrong with its stomach.” But on a pig farm, vomiting is precisely a signal that is easily “misread”—it is rarely an isolated gastrointestinal problem. More often, it is a way for systemic disease, poisoning, or metabolic disorders to manifest in the digestive tract.
Vomiting is, in essence, a reflexive emptying action triggered when the vomiting center in the medulla oblongata is activated. This center can be activated by direct irritation of the gastrointestinal mucosa (such as by viruses or toxins), pyrogens and poisons in the blood (such as in septicemia or metabolic disorders), direct damage to the nervous system (such as encephalitis), or even reflexive retching caused by severe coughing. Treating vomiting as “a symptom” rather than “a disease” is the first step in identifying its cause.
One: The condition that must be ruled out first—African Swine Fever
Under current disease-control conditions, the first step when pigs vomit is not to suppress the vomiting, but to rule out African swine fever. Highly virulent African swine fever virus can invade multiple organ systems throughout the body, including the digestive tract. Vomiting is indeed one of its clinical signs, but it rarely occurs in isolation.
The combination of signs to watch for includes: a persistent rise in body temperature to 40.5—42°C; purplish-red hemorrhagic spots on the edges of the ears and along the flanks; complete loss of appetite; profound depression; constipation or bloody diarrhea; and a high mortality rate. If vomiting occurs together with several of these signs, the correct response is to isolate the pigs immediately, collect samples for testing, and report the case to the competent authorities—not to administer antiemetics first and wait to see what happens. Putting African swine fever first on the list of conditions to rule out is a responsibility to the entire pig farm.
II. Viral Diarrhea: Vomiting Is the “Prelude”; Diarrhea Takes Center Stage
Porcine epidemic diarrhea (PED) and transmissible gastroenteritis (TGE) are the most common viral causes of vomiting in pigs and pose the greatest threat to piglets in particular. The clinical course of the two diseases is very similar: vomiting occurs first, followed within a few hours by a rapid onset of severe watery diarrhea. The feces are grayish-yellow or gray and foamy, dehydration occurs very quickly, and piglets may lose 25% of their body weight within 24 hours. The vomit is often a yellow or yellow-green, bile-like fluid, appearing when the stomach is empty or in the early morning. Similar signs then appear in other pigs in the same pen.
TGE causes an extremely high mortality rate in piglets up to 2 weeks of age; pigs older than 5 weeks can usually survive it. PED spreads somewhat more slowly than TGE, but vomiting and diarrhea are likewise its core signs. The clinical significance of distinguishing between the two is not to “treat” them, but to assess herd risk and immune status—neither has a specific treatment, and prevention and control center on vaccinating sows according to gestational stage before farrowing, and strict disinfection and isolation in the farrowing room.
Pseudorabies in pigs also causes vomiting in newborn piglets, but its distinguishing feature is prominent neurological signs: circling, convulsions, foaming at the mouth, and lethargy. Vomiting often occurs at the same time as, or before or after, the neurological signs, and the mortality rate is extremely high. Porcine hemagglutinating encephalomyelitis (vomiting and wasting form) is characterized by “vomiting + severe wasting + drinking large amounts of water.” The vomit is not accompanied by marked diarrhea. Affected pigs die of dehydration due to difficulty swallowing, and the disease course is more wasting in nature than acute watery diarrhea.
III. Toxic factors: Vomiting is the body’s first response to “eliminate toxins”
Mycotoxins, especially vomitoxin (DON), are among the most easily overlooked and most common non-infectious causes of vomiting on pig farms. Pigs are extremely sensitive to vomitoxin; even a low dose of 50μg/kg of body weight can trigger vomiting. Vomitoxin levels of 2—4ppm in feed can cause stunted growth, and 2.6ppm fed for 8 weeks can cause obvious liver lesions. Symptoms occur shortly after eating, and feed residues with mold spots may be visible in the vomit. Pigs in the same group eating the same feed may develop symptoms one after another. In winter and humid seasons, toxin accumulation due to untimely cleaning of feed bins and feed lines is a common scenario for this route.
Vomiting caused by salt poisoning is accompanied by a distinct combination of neurological signs: dramatically increased thirst, drooling, muscle tremors, circling, and ataxia; in severe cases, the animal may sit like a dog or develop opisthotonos. The underlying cause is usually insufficient drinking water combined with excessive salt in the feed. Slowly providing clean drinking water is key to treatment; do not provide a large amount of water all at once.
In addition, organophosphate pesticide poisoning causes drooling, vomiting, constricted pupils, muscle tremors, and difficulty breathing, while rodenticide (anticoagulant) poisoning is characterized by lameness, lethargy, and black, tarry feces. A common feature of these types of poisoning is that pigs in the same group or pen fall ill one after another within a similar time frame, with a traceable history of exposure to the toxic substance.
IV. Problems with the digestive system itself: gastric ulcers and parasites
Gastric ulcers are a common cause of vomiting in finishing pigs and adult sows, but the vomiting has a very distinct “time signature.” Sick pigs usually retain their appetite, but after eating a certain amount, the resulting gastric irritation is too intense, and they vomit. After vomiting, they feel hungry again, forming a cycle of “eat, vomit; vomit, eat,” and gradually lose weight. The color of the vomit is a key distinguishing clue: coffee-ground-like, brown, or streaked with blood suggests gastric bleeding. These pigs often also have pale skin and black, tarry feces. Triggers include feed ground too finely (with insufficient coarse fiber), diets lacking vitamin E, vitamin B1 and selenium, long-term high-energy corn diets, and chronic irritation from mycotoxins.
Vomiting caused by parasites is not uncommon in weaned and finishing pigs. Strongyloides parasites live in the small intestine; affected pigs vomit and also have enteritis, diarrhea, and rapid weight loss. Roundworms primarily affect pigs aged 3–6 months and can cause “runts,” characterized by anemia, diarrhea, vomiting, and progressive weight loss. Stomach worm infections present as poor appetite, increased thirst, vomiting, and jaundice, along with weight loss. A distinguishing clue for parasite-related vomiting is that it is not frequent, but is accompanied by long-term digestive and absorptive dysfunction and declining body condition. An irregular deworming history is important background information.
V. An Underestimated Diagnostic Dimension: The Color of the Vomit and When It Occurs
Before laboratory testing, the color of the vomit and the time when vomiting occurs can eliminate more than half of the possible causes.
Check the color: Undigested feed pellets—first investigate esophageal obstruction, eating too quickly, or a relaxed cardia; this is “regurgitation,” not true vomiting. Yellow or yellow-green frothy liquid points to bile reflux and strongly suggests viral enteritis such as TGE/PED, often progressing to watery diarrhea within hours. Coffee-ground-like material or fresh red streaks directly point to gastric ulcers or gastric bleeding. Clear or white foamy mucus often does not originate in the gastrointestinal tract; instead, a reflex dry heave may be triggered by severe coughing due to swine influenza or acute pleuropneumonia. After vomiting, the pig may pant and have a runny nose; focus on checking its temperature and breathing.
Check the timing: Vomiting immediately after eating is usually due to a mechanical obstruction or feed that is too irritating. Vomiting sour-smelling, mushy material 1–2 hours after eating suggests impaired gastric emptying, commonly seen with acute gastritis or early duodenal ulcers. Vomiting yellow fluid on an empty stomach (at dawn or after an overnight fast) is an early warning sign of viral diarrhea.
Six. Prevention and control approach: Find the “culprit” first, then consider antiemetics
Step one, rule out African swine fever first in the diagnostic process. If any combination of vomiting, high fever, skin hemorrhages, and high mortality occurs, isolate and submit for testing first; do not delay by self-medicating.
Step two, narrow down the possible cause based on “color + timing + accompanying symptoms.” Vomiting with watery diarrhea → consider viral enteritis; vomit containing blood or resembling coffee grounds → consider gastric ulcers; vomiting shortly after feeding, with multiple cases in the same group → consider mycotoxins or feed-related problems; vomiting with neurological symptoms → consider pseudorabies, hemagglutinating encephalomyelitis, or salt poisoning; vomiting with prolonged weight loss and irregular deworming → consider parasites.
Step three, treat the underlying cause rather than simply stopping the vomiting. There is no specific drug for viral diarrhea; the core measures are fluid replacement to prevent dehydration, prepartum immunization of sows, and disinfection and isolation in the farrowing room. In cases of mycotoxin poisoning, immediately replace the raw materials and add a mycotoxin binder; decisively discard severely moldy feed. For gastric ulcers, adjust feed particle size, increase crude fiber, and supplement with vitamin E and selenium; use acid-suppressing and gastric mucosal protective drugs if necessary. For parasitic infections, implement a regular whole-herd deworming program; mix albendazole and ivermectin into the feed and use for 7 days, with an additional treatment before piglets are moved between groups.
Step four, treat vomiting as a “herd signal,” not an “individual event.” Vomiting in one pig may be an individual problem, but if pigs in the same pen or group begin vomiting one after another within a similar period, look for common causes related to feed, water sources, ventilation, and immune status. The value of vomiting in disease control lies not in stopping one pig from vomiting, but in using it to identify the variable affecting the whole herd. (Source: Zhang Weiguang)