Pig Housing Ventilation: The Rules That Prevent Respiratory Disease

Respiratory disease is the silent killer of the pig industry. A pig with chronic pneumonia grows 10-15% slower, eats more feed per kg of gain, and is more susceptible to other infections. By the time you hear coughing, 30-50% of your herd is already infected. And in 80% of cases, the root cause is not a virus or bacteria — it's the ventilation system [1][2].

The good news: pig housing ventilation is not complicated. There are 6 rules that, if followed, eliminate 90% of respiratory problems. The bad news: most smallholder pig houses in tropical Africa violate at least 4 of these rules — usually because farmers prioritize keeping heat in over getting air through.

The 6 ventilation rules

1. Air in at the bottom, air out at the top. Fresh air enters through low openings (curtains, vents at pig height) and exits through high openings (ridge vents, roof gaps). This creates a natural convection current — warm, moist, contaminated air rises and exits, fresh air is drawn in to replace it. Reversing this (high intake, low exhaust) pushes contaminated air back down to pig level.
2. Minimum ventilation rate: 0.3 m³ per minute per pig in winter, 1.0 m³ per minute per pig in summer. Below this rate, ammonia and humidity build up. Above it, drafts cause chilling (especially for young pigs). The minimum applies even at night — closing all ventilation at night is the #1 cause of pneumonia outbreaks.
3. No direct drafts on pigs. Air entering the house must be deflected, not blown directly on the pigs. Use deflectors, perforated ceilings, or place intake vents high enough that the incoming air mixes with the warmer house air before reaching pig level.
4. Relative humidity 50-70%. Above 70%, bacteria and viruses survive longer in the air. Below 50%, dust levels rise (irritates the respiratory tract). Use a simple hygrometer (~3,000 FCFA) and adjust ventilation accordingly.
5. Ammonia under 20 ppm at pig level. Above 20 ppm, the respiratory cilia (tiny hairs that clear mucus from the lungs) become paralyzed, opening the door to infection. Crouch to pig nose level and smell — if it burns your eyes or you can't stay 30 seconds, ammonia is too high.
6. Stocking density: 0.7-1.0 m² per grower pig (50-100 kg). Overcrowding increases air contamination, stress, and disease transmission. Pigs packed too tightly cannot establish a dunging area separate from a sleeping area — meaning they breathe air contaminated with their own feces.

The tropical climate ventilation design

In Cameroon and similar tropical climates, the design challenge is opposite to temperate climates. You're not trying to keep heat in — you're trying to let heat out while keeping rain and direct sun out. The recommended design:

Roof

• Height: 2.5-3.5 m at the eaves, 3.5-4.5 m at the ridge. Tall enough for air to circulate. Short houses are hot houses.
• Ridge vent: 30-50 cm wide opening along the entire length of the ridge. This is the exhaust. Hot air rises and exits here. Cover with a cap to keep rain out while letting air pass.
• Roof material: corrugated metal with a ceiling. Metal alone radiates heat down onto the pigs. Install a simple plywood or thatch ceiling 30-50 cm below the metal roof — the air gap acts as insulation.
• Roof overhang: 1-1.5 m on all sides. Keeps rain out even when side curtains are open for ventilation.

Walls

• Lower 1 m solid (concrete block, brick, or wood). Protects pigs from wind, contains the dunging area.
• Upper 1-1.5 m: open or curtained. This is the air intake. Use roll-up curtains (canvas or plastic) that can be opened during the day and partially closed at night.
• Never fully close the upper walls at night. Even in the coldest harmattan night, leave at least 20 cm of the curtain open. Pigs produce 0.3-0.5 L of water per pig per night just by breathing — without ventilation, that water condenses on cold surfaces and the air becomes saturated with ammonia.

Floor and dunging area

• Solid concrete floor with 2-3% slope toward a drain. Easy to clean, drains urine and water.
• Designated dunging area at the back wall (away from feeding). Pigs naturally dung in one corner if given the chance. Clean this daily.
• Slatted floor option (for finishers): 30% of the floor slatted over a manure pit. Pigs defecate on the slats, manure falls through. Reduces ammonia dramatically but requires careful management.

The 5 ventilation mistakes that cause pneumonia

1. Closing the house completely at night. #1 mistake. Even in cold weather, leave some ventilation. Pigs are not as cold-sensitive as humans think — adult pigs tolerate 10-15°C fine. They are far more sensitive to ammonia and humidity than to cold.
2. Putting the air intake at the top. Common mistake — the farmer thinks hot air rises so they put intake at the top. Wrong. Hot air rises and EXITS at the top. Cold fresh air ENTERS at the bottom. Reverse the design.
3. Overcrowding. Pigs at 0.5 m² each = guaranteed respiratory disease. Each pig needs at least 0.7 m² (growers) or 1.0 m² (finishers). Count your pigs and divide by your floor area.
4. No manure management. Manure sitting in the pen releases ammonia continuously. Clean daily. If using deep litter, top up with fresh bedding weekly and remove the old litter completely between batches.
5. Using exhaust fans pointed at pigs. Fans should pull air OUT of the house, not blow air directly on pigs. If you use a fan, mount it near the ridge vent pointing outward.

The 4-week deep-clean protocol

Even with perfect ventilation, you need to deep-clean the house every 4 weeks to break disease cycles. The protocol:

1. Move pigs to a temporary enclosure (or sell the batch if ready).
2. Remove all manure, bedding, and feed residue. Compost the manure for 6 weeks before using as fertilizer.
3. Wash walls, floor, and feeders with high-pressure water and detergent.
4. Disinfect with 2% sodium hydroxide (caustic soda) or 3% formalin. Wear protective gear. Let sit for 2 hours.
5. Rinse thoroughly with clean water.
6. Let dry completely — at least 24 hours, ideally 48 hours. Dryness kills most bacteria and viruses.
7. Re-bed with fresh shavings before pigs return.

The cost: 5,000-8,000 FCFA in disinfectant + 1 day of labor. The benefit: 80-90% reduction in respiratory disease in the next batch [1][3].

The emergency ammonia response

If you walk into the pig house and your eyes burn or you can't stay 30 seconds, ammonia is above 50 ppm. Emergency protocol:

1. Open all curtains and vents immediately. Maximum ventilation for 30 minutes.
2. Remove all manure from the pens. This is the source of the ammonia.
3. Add fresh dry bedding. Dry shavings absorb moisture and reduce ammonia release.
4. Check the water lines for leaks. Wet manure releases 10x more ammonia than dry manure.
5. Reduce stocking density if possible. Move some pigs to another pen.

Repeat every morning until ammonia is below 20 ppm (no eye irritation, you can stay 5+ minutes).

FarmWise generates a daily "Muck out & refresh bedding" task for every active pig pen — the easiest way to keep ammonia under control. Tapping it complete also serves as a record: if respiratory disease appears in 2 weeks, you can see exactly which days the bedding was changed.

Sources & References

• [1] Pig333: Ventilation in Pig Housing — 80% of respiratory disease traces to poor ventilation, ammonia threshold of 20 ppm. Source: pig333.com
• [2] National Hog Farmer: Respiratory Disease in Grower Pigs — pneumonia slows growth by 10-15%, by the time coughing is audible 30-50% of herd is infected. Source: nationalhogfarmer.com
• [3] Iowa State University Extension: Pig Housing Ventilation Design — minimum 0.3 m³/min/pig in winter, ridge vent + low intake design. Source: extension.iastate.edu