As soon as the cold season arrives, coughing and wheezing start up on pig farms. First, one or two pigs develop a dry cough in the morning and evening. Three to five days later, the whole barn is wheezing, feed intake has dropped, and the feed-to-meat ratio has climbed. Many farms respond to coughing and wheezing by quickly adding medication, taking turns using tilmicosin and florfenicol. But as soon as the medication is stopped, the illness returns. A lot of money has been spent, yet the pigs have never been truly stable.
Respiratory diseases are difficult to manage in autumn and winter. The root cause is not that the pathogens are especially strong, but that the underlying environment has already deteriorated. Cold stress, ammonia, and dust combine to continuously damage the pigs’ respiratory mucosal barrier, giving pathogens an opportunity to take hold. Relying solely on more medication is like filling a pit that can never be filled; control the environment, and medication can finally do its job effectively.
First, understand why respiratory illnesses are so hard to keep under control in autumn and winter.
Temperature differences are the first crack. Pigs have almost no sweat glands and rely heavily on breathing to dissipate heat. When daytime temperatures are high, their pores open and metabolism speeds up. When cold air arrives at night, their pores constrict and blood circulation slows. Their respiratory mucosa is repeatedly damaged by alternating hot and cold conditions. Some data show that for every 5°C drop in ambient temperature, the incidence of respiratory diseases in pigs increases by about 30%; when the day-night temperature difference exceeds 8°C, pigs’ cortisol levels rise by 40%–60%, significantly suppressing immune function.
The conflict between insulation and ventilation comes to a head. Afraid that the pigs will get cold, many pig farms seal up the doors and windows, allowing ammonia and hydrogen sulfide to accumulate inside the barns. When the ammonia concentration exceeds 20 ppm, respiratory cilia begin to fall out and become paralyzed, leaving the respiratory tract completely exposed. In an environment with an ammonia concentration of 30 ppm, nursery pigs’ daily weight gain decreases by 12%, the feed-to-meat ratio increases by 0.3, and the incidence of respiratory disease rises by 40%. If people can enter the barn without a stinging nose or burning eyes, ventilation is basically adequate; if the ammonia smell hits you as soon as you walk in, you need to ventilate regardless of how cold it is outside.
Mycoplasma is a “trigger factor.” In cases of lung infection in fattening pigs, 40%—80% test positive for Mycoplasma. Mycoplasma first damages the respiratory ciliary barrier, making it easier for pathogens such as PRRS virus and Actinobacillus pleuropneumoniae to take advantage. To prevent and control respiratory disease complexes, Mycoplasma must be addressed first.
Step two: Environmental management—address the “root cause”
First: Control temperature differences and block cold drafts
Target temperatures for pig barns at each stage: nursery barn 26—28℃, finishing barn 25—30℃, farrowing room 28—32℃, gestation barn 26—29℃. Keep the day-to-night temperature difference within 5℃ as much as possible, and no more than 8℃.
In practice, before the sun sets in the evening, partially close the windows and roll-up curtains on the north-facing and windward sides. Don’t wait until the pigs huddle together in the middle of the night to take action. Run the back of your hand around door gaps, fan openings, and damaged curtains. Any spot where you can feel a cool draft is a source of a cold draft. Seal it with foam sealant, burlap sacks, or plastic sheeting. A cold draft blowing directly onto a pig’s back harms it more than lowering the overall temperature by two degrees.
Second: Ventilate properly to reduce ammonia and moisture
Ventilation and insulation are not an either-or choice. Leave a small vent open at night for continuous air exchange; the ammonia smell should not be irritating. Ventilate during the warmest part of the day, from 10 to 3, for 1—2 hours each time. Open a small window gap for slow ventilation; do not open windows wide and create a cross-draft that blows directly onto the pigs. Large-scale farms should use variable-frequency fans set to the minimum ventilation rate, ensuring that ammonia remains below 15 ppm at all times.
In autumn and winter, switch to cross ventilation, allowing air to enter through side-wall or roof inlets, flow slowly across the barn, and then exit, avoiding cold air blowing directly over a long distance into the lying area. Prefer roof inlets or side-wall inlets with deflectors, so that cold air first reaches the upper part of the barn, mixes with the warm air, and then slowly sinks.
At the same time, remove manure daily and do not leave manure and urine overnight to reduce ammonia production at the source. Keep indoor humidity at 60%—70%; when it exceeds 75%, ventilation must be increased to remove moisture.
Step three: Control dust and cut off pathogens’ “free ride”
In autumn, the climate is dry, and there is much more feed dust and manure dust in pig barns than in summer. These dust particles carry pathogens such as Mycoplasma, Actinobacillus pleuropneumoniae, and Streptococcus, which are inhaled directly into the pigs’ alveoli. Three ways to reduce dust: During midday ventilation, use a sprayer to apply a small amount of water so the dust settles. Note that this means “light spraying,” not pouring large amounts of water; replace dry sweeping with wet sweeping or vacuuming; add an appropriate amount of oil to the feed (1%—2%). This can both reduce feed dust and provide energy.
Three. Immunity and medication: doing the right thing at critical junctures
Immunization and prevention: Mycoplasma is a key focus
The foundation of mycoplasma control is environmental management—warm, dry, and well ventilated conditions, with lower rather than higher stocking density, and strict all-in/all-out management. On this basis, implement mycoplasma vaccination according to protocol: during the suckling stage, inject Su Beizhi at castration/tail docking0.3—0.5mL, and inject 0.7—1mL on the day of weaning. In autumn, also prioritize boosting immunity through core vaccines against classical swine fever, foot-and-mouth disease, PRRS, circovirus, pseudorabies, and contagious pleuropneumonia. Strictly follow the one-needle-per-pig procedure, maintain proper cold-chain storage and transport of vaccines, and monitor antibody levels after immunization.
Medication-based health care: time it to stress points
Medication-based health management is not about “adding medication whenever nothing seems wrong”; it means administering medication preventively in advance of stress points such as widening temperature differences, regrouping, and immunization.
For group prevention, add 20% tilmicosin premix at 1000—2000 grams and 10% doxycycline at 500—1000 grams per ton of feed, together with Ma Xing Shi Gan San at the dosage specified in the instructions, and mix into the feed for 7—10 consecutive days. Tilmicosin and doxycycline primarily target mycoplasma and bacterial respiratory infections, while Ma Xing Shi Gan San clears the lungs and relieves wheezing. Combining Chinese and Western medicine provides broader coverage. If pigs’ feed intake declines and they do not finish feed mixed with medication, switch to medication in drinking water: administer tilmicosin or florfenicol soluble powder together with electrolytes, multivitamins, and vitamin C for 5—7 consecutive days.
Individuals showing coughing, wheezing, or abdominal breathing should first be isolated, then given targeted injections to prevent spread throughout the group. Inject florfenicol injection into the neck muscle at 15 milligrams per kilogram of body weight, once every 48 hours, for 2 doses. For severe breathing difficulty, aminophylline may be administered separately under veterinary guidance to relieve respiratory distress.
Do not cross these medication safety red lines: Tilmicosin must never be used together with epinephrine and should not be used at the same time as florfenicol or lincosamides. Florfenicol is prohibited for piglets weighing less than 2 kilograms, during vaccination, and in adult breeding boars. Strictly observe the withdrawal period before slaughter: the withdrawal period for florfenicol injection in pigs is 16 days; for tilmicosin, it is generally 14–21 days.
Four. Pen-round warning: Stop losses at “the first cough”
During daily pen rounds, record changes in the pigs’ feed intake, body temperature, and feces, and focus on three types of signals:
Early warning signs: the pigs become less alert, stop after rooting at the feed a couple of times, and occasionally have a dry cough. These signs are especially noticeable when the temperature difference between morning and evening is large. At this point, don’t rush to medicate the entire herd. First check for drafts, ammonia, and dust, and make the necessary environmental adjustments. Many mild cases of coughing and labored breathing will resolve on their own.
Intermediate-stage signs: the cough changes from dry to wet (with audible phlegm), the breathing rate increases, and the abdomen moves noticeably with each breath. At this point, improve the environment while providing medication as a preventive measure according to the plan above, and isolate individuals with pronounced symptoms.
Danger signs: Pigs lying down and unable to get up, rapid breathing, and open-mouth breathing. Without timely intervention, they may die within 1—2 days. This situation often indicates secondary infection with pleuropneumonia or PRRS. Immediately isolate the pigs, administer targeted injections, and collect samples for testing to identify the pathogen.
Summary
Respiratory diseases on pig farms in autumn and winter are rarely caused by a single pathogen. They result from the convergence of three factors: temperature fluctuations, poor air quality, and weakened immunity. Relying on medication alone may suppress the problem today, only for it to recur tomorrow.
The key to prevention and control is to manage the day–night temperature difference, block drafts, keep ammonia below 15 ppm, control dust, and make mycoplasma prevention and control the top priority. On this basis, follow immunization protocols and use medication appropriately. Once the environment is under control, the pigs’ respiratory mucosal barrier can be protected, allowing medication to work effectively.
Remember this: half of respiratory disease in pigs is caused by cold, and the other half by stuffy conditions. Turn “keeping warm” and “ventilation” from an either-or choice into a both-and choice, and the herd can get through this winter safely.