Heat waves on pig farms: Best practices to follow before, during, and after a heat wave

• Dust off the air intakes and clean the inside of the ventilation ducts.
• Calibrate the temperature sensors and check that doors and windows are open.
• Check the maximum exhaust airflow of the fans (see table below).
• Reduce stocking density toward the end of the finishing period: quickly send the heaviest animals to the slaughterhouse to free up space.

Heat stress begins as soon as the temperature exceeds 24°C.

• Comply with standards for water flow rate and trough length to limit competition among animals.
• Provide summer diets, particularly for pigs nearing the end of the finishing phase and lactating sows. These feeds are less thermogenic: they reduce total nitrogen content without reducing essential amino acids, maintain a minimum fiber content, and include added fat for lactating sows. Follow recommendations for salt, vitamins, and antioxidants to maintain the animals’ hydration and resilience.

• Order more gilts in the first half of the year to ensure adequate herd size.
• Protect gilts from the heat (delayed puberty and infertility) and plan ahead for boar replacement (>10–12 months).
• Ensure a reliable supply of doses: protective diluents, delivery in an air-conditioned vehicle, and a cool, alarm-protected receiving area.
• Conduct a reproductive health audit and assess seasonal infertility as early as the previous winter.
• Plan ahead for training replacement staff and adjust work schedules during hot periods.

• Observe the animals (signs of heat stress): respiratory rate, lying on their sides and away from other animals, and reduced visits to feeders.
• Increase air intake areas (open windows/doors to allow cross-ventilation; use PVC tubes in the farrowing room).
• Create airflow over the animals (a perceived temperature drop of -1 °C for every +0.1 m/s increase above 0.2 m/s), exercising caution in the farrowing room.
• Adjust the ventilation controller (reduce the control range, often from 6 to 4 °C) and verify the actual maximum airflow rate.
• Sprinkle water on the animals outside the pens (never directly inside the pen) and never exceed 80% relative humidity.
• Mist water at the air inlets, preferably at high pressure (≈90 bars); do not use pre-soaking systems.
• In deep-bed systems, clean out the straw-bedded area during the current batch and replace it with a layer of clean straw.

• Schedule interventions and meal distribution before 10 a.m. or after 10 p.m. to avoid midday activity peaks.
• Increase water intake (provide water between gruel meals, without diluting the gruel) and ensure piglets have access to water.
• Schedule feedings during cooler hours: recommended times are 5 a.m., 10 a.m., and 11 p.m. rather than 8 a.m., 1 p.m., and 6 p.m.
• Reduce the amount distributed at each feeding and split the ration (additional feedings at night; eliminate the afternoon feeding in the farrowing house).
• If possible, provide a specialized feed rich in antioxidants (vitamins E and C, selenium, polyphenols) during heat waves. Use sodium formate instead of sodium bicarbonate to maintain electrolyte balance.

• Enhance estrus stimulation and detection (grouping, showering, and pheromones), carry it out during the cooler hours of the day, and maintain two checks per day.
• Protect semen doses: store at 17°C (±2°C, between 15 and 20°C) in the dark; place in an air-conditioned storage unit within 15 minutes and check daily.
• Use flexible insemination protocols and do not systematically increase the number of inseminations; inseminate 20 to 30% more sows.
• Limit natural matings during and after the heat wave (boar semen quality is impaired for 4 to 6 weeks).
• Increase the frequency of ultrasound pregnancy checks during and after the heat wave.
• In the farrowing house: keep sows cool and hydrated, treat any hyperthermia (>39.5 °C) promptly, and provide additional assistance during farrowing.

• Paint roofs and walls in light colors; plant ground cover or trees in front of air intakes.
• Limit direct sunlight (install sunshades on south- or west-facing windows).
• Consider investing in a cooling system (be careful with sizing, as it can restrict airflow) or a ground-source heat exchanger (pipes buried 2 m deep, with soil temperature close to 12 °C year-round).
• Gradually return to the normal diet, while continuing to provide the “emergency” feed for a few days; monitor the return of appetite and watch for diarrhea, a sign of digestive fragility.

• Negative effects can persist for several weeks to several months: delayed returns to estrus, late abortions, stillbirths, and infertile boars.
• Avoid accumulating return-to-service sows and empty sows; cull to rebalance the herd’s demographics.
• Conduct a post-heatwave reproductive assessment (analysis of heat stress episodes, etc.) to identify the most vulnerable stages.