When checking the pens on a pig farm, people tend to become alert and take action immediately if piglets have a fever, diarrhea, or coughing and labored breathing. But what if the piglets feel normal to the touch (no fever), show no obvious diarrhea or coughing and labored breathing, and are simply listless overall, huddling together and lying down, and do not even look at the feed when it is offered?
Many farmers think, “If they don’t have a fever, it probably isn’t serious. They’ll be fine after missing a couple of meals or waiting a couple of days.”
This is an extremely dangerous misconception. “No fever + listless and not eating” does rule out the initial stage of acute septicemia or an acute, highly virulent infectious disease, but it often points to two other, more difficult problems: either environmental stress has pushed the piglets’ physiological limits, or a chronic wasting disease is quietly draining the herd’s reserves. By the time the piglets are too weak to stand, intervention has often missed the best window.
Based on the clinical signs, when piglets show this pattern, the main possibilities to consider are:
I. Environmental and physiological stress (the most common and easiest to overlook)
Piglets have very poor temperature-regulation abilities and little subcutaneous fat. When the environment changes slightly, they may not develop a fever, but they can go straight on “strike.”
1. Cold stress and drafts: In autumn and winter or early spring, if the heat lamp is not warm enough, or if drafts blow directly through the nursery (especially chilling the abdomen), piglets instinctively reduce activity (become listless) and huddle together in piles to conserve heat. Blood is diverted from the digestive system to the body surface to keep warm, and gastrointestinal motility comes to a halt, so naturally they “stop eating.”
2. Weaning and relocation stress: Piglets that have just been weaned or relocated have been separated from the sow and their familiar environment, leaving them in a state of extreme panic. Their feed changes from liquid breast milk to solid dry feed. The piglets’ intestinal villi atrophy, and indigestion causes feed to accumulate in the stomach, resulting in a complete lack of appetite.
Two. Chronic wasting diseases (the “hidden killer” of pig farm profits)
When a pathogen is not highly virulent, or when piglets have some antibodies, pigs may not develop a high fever but instead enter a chronic wasting process.
1. Post-weaning multisystemic wasting syndrome (Porcine circovirus 2 type): This is the most typical cause of “not eating without a fever.” Infected piglets usually have a normal or low body temperature, are extremely lethargic, progressively lose weight, and have pale or yellowish skin and a rough, unkempt coat. Because their immunity is often compromised, they eventually die from secondary infections.
2. Chronic Glässer’s disease: Pigs with Glässer’s disease develop a fever during the acute stage, but in the chronic stage they often show reduced feed intake and weight loss, and are frequently accompanied by breathing difficulties (abdominal breathing) or mild joint swelling. Piglets may refuse to eat because of underlying pain and weakness.
3. Mild classical swine fever or infection with a low-virulence strain: This is particularly possible on farms with an unclear immune status, where piglets may be infected with mild classical swine fever or a low-virulence ASF strain. These pigs usually show only persistent lethargy and anorexia; their temperature may be normal or they may have only a brief, mild fever, after which they enter a chronic carrier state.
III. Occult gastrointestinal conditions and mild inflammation
1. Gastric ulcers or feed accumulation: If piglets are suddenly switched to a different feed, or eat feed that has been ground too finely, they can easily develop stomach discomfort or even mild ulcers. They may experience stomach pain and have very little desire to eat, usually accompanied by a hunched back and a curled-up abdomen.
2. Mild enteritis or parasites: Some forms of enteritis (such as coccidiosis or chronic Escherichia coli infection) do not cause a fever throughout the body in the early stages, and cause only mild intestinal discomfort. Piglets may refuse feed because their stomachs feel uncomfortable. In addition, heavy infestations of internal parasites such as roundworms can lead to malnutrition, lethargy, and reduced appetite in piglets.
3. Oral problems: These include gingivitis or oral ulcers in piglets, or tooth fractures and infection caused by improper tooth clipping. Eating then causes pain, leading them to refuse feed.
Rapid On-Site Troubleshooting Guide
When you find piglets like these, don’t inject them blindly. First, take three steps:
1. Check the skin and coat: Pale skin, a rough coat, and cool ear edges often suggest chronic wasting (circovirus, parasites, or anemia); localized red patches on the skin may indicate a chronic infection or an allergy.
2. Check the abdomen and breathing: A sunken abdomen suggests malnutrition or dehydration; a slightly swollen abdomen with a drum-like sound when tapped may indicate indigestion or enteritis. If there is also pronounced abdominal breathing, focus on ruling out Glässer’s disease or mycoplasma.
3. Feel the base of the ears and the body surface: Even if there is no fever, feel the base of the ears and the limbs for coolness (which may indicate cold stress or anemia), or check for any localized areas that feel hot (which may indicate localized chronic inflammation).
Treatment plan: first “rescue the environment,” then “regulate the gut,” and finally “treat the disease.”
Step one: Immediately improve the microenvironment
If it is caused by cold stress, immediately raise the temperature of the incubator or nursery (to about 2℃ above the usual standard) and check for direct drafts. You can lay down dry mats to make the piglets more comfortable. Once the environment warms up, many piglets with mild loss of appetite can recover that same day.
Step two: Appetite stimulation and gastrointestinal conditioning
For piglets refusing feed, never force-feed large amounts of dry feed or cold water. You can mix a small amount of creep feed with warm water (adding a little glucose or milk powder) and apply it to the piglets’ lips to encourage them to lick it. At the same time, add electrolytes and multivitamins, vitamin B complex, and probiotics to their drinking water to help restore gastrointestinal function and stimulate appetite. If parasites are suspected, deworm the entire group.
Step three: Check the group and administer targeted medication
If it occurs in individual pigs: isolate the sick pig, administer an intraperitoneal injection of glucose saline (to replenish energy), and give an intramuscular injection of compound vitamin B (to promote gastrointestinal motility). If it is a gastric ulcer, cimetidine can be injected or omeprazole can be given orally.
If the whole group shows lethargy and weight loss: be highly alert to circovirus or chronic Glässer’s disease. It is recommended to collect blood and lymph node samples from sick pigs immediately and send them for testing. If caused by circovirus, the focus is on improving management and controlling secondary infections (for example, adding tylvalosin + doxycycline as a preventive measure), and evaluating the circovirus vaccination schedule for the sow herd.
Key reminder: A virulent ASF strain is currently circulating. If piglets that “have no fever, are listless, and won’t eat” appear sporadically and continuously in the herd (especially if accompanied by pale skin, swollen joints, or mild respiratory symptoms), and antibiotic treatment is ineffective, be sure to collect samples for nucleic acid testing immediately. Rule out ASF before treating it as an ordinary disease—this is an ironclad rule.
In closing:
The thing pig farmers fear most is “boiling a frog in warm water.” A pig that has no fever and won’t eat is like a frog in warm water: although nothing dramatic is happening on the surface, its strength is being drained day by day. When you find a lethargic pig, first check whether its surroundings are too cold, then see whether the feed has changed, and only consider illness last. Finding the source is the only way to recover these “hidden losses” from the pig farm. (Source: 张伟光)