Heat Stress Management in Pigs

As temperature and humidity increase, pigs are more likely to experience higher mortality rates, slower growth, reduced fertility in boars, increased embryonic losses, lower ovulation rates, and delayed estrus in sows and gilts—especially if proper comfort measures are not maintained.

Key Points to Consider

Effective management during hot weather should focus on proper pig handling, checking water supply systems, maintaining cooling and ventilation, following safe transport practices, and managing seasonal infertility.

Pig Handling

Special care should be taken while moving pigs during hot conditions. Animals should be handled gently, kept calm, and moved slowly. Avoid loud noises and rapid movement, as these can increase stress levels.

Moving pigs in very large groups (more than five animals) can make them more excitable and prone to overheating. Prolonged standing during loading or movement should be minimized, especially in hot weather.

It is advisable to shift handling and transportation activities to cooler parts of the day, such as early morning or late evening, since heat significantly increases stress during movement.

Signs of Heat Stress in Pigs

Be alert for the following symptoms:

• Open-mouth breathing
• Patchy or blotchy skin
• Excessive vocalization
• Stiff movements
• Muscle tremors
• Increased heart rate
• Elevated body temperature

Management of Nursery and Finisher Pigs

1. Maintain cooling and ventilation systems

Ensure that fans, air inlets, and drip/spray cooling systems are functioning properly. Worn-out fan belts can reduce ventilation efficiency and should be replaced. Cooling system nozzles may become blocked due to sediment buildup and should be inspected and cleaned regularly.

2. Provide sufficient water supply

Water intake increases during hot weather. Nursery pigs require about 1 gallon of water per day, while finishing pigs may need up to 5 gallons daily. Check nipple drinkers to ensure proper flow rates so that pigs can meet their water requirements.

3. Avoid overcrowding

High stocking density worsens heat stress. Providing adequate space helps reduce aggression and improves overall performance.

• Nursery pigs: approximately 1.7–2.5 sq. ft. per pig
• Finisher pigs: space should increase with growth, from about 5 sq. ft. at 50 kg to around 8 sq. ft. at 100 kg (market weight)

4. Care during transportation

During transport, loading and unloading should be done quickly, without unnecessary stops. Animals should be lightly wetted before transport on hot days. Trucks must allow maximum airflow, and using damp sand or wet bedding materials can help keep pigs cool.

Management of Breeding Herd

Seasonal infertility is a common issue in pig production. If a herd is known to be affected, breeding targets should be adjusted to compensate for reduced reproductive performance. This may involve increasing the number of females bred by up to 40%, depending on the decline in farrowing rate.

Breeding intensity should gradually increase during the hotter months (May to August) and return to normal levels by September.

High temperatures reduce feed intake in females, which affects their recovery after farrowing. This leads to longer intervals between weaning and estrus and lowers ovulation rates.

Boar Management in Hot Weather

Maintaining boar fertility is equally important. Exposure to temperatures above 80°F (≈27°C) for even two weeks can significantly increase abnormal sperm production and reduce sperm motility. Recovery from heat stress may take at least four weeks.

Boars may also become less active and show reduced libido during hot periods.

Respiration rate is a useful indicator of heat stress:

• Normal: 25–35 breaths per minute
• Heat stress: 75–100 breaths per minute

When respiration reaches around 40–50 breaths per minute, immediate cooling measures should be implemented to prevent further stress.