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Ventilation Basics For Swines

by 5m Editor
13 November 2006, at 12:00am

By Mark Storlie, ISU Extension Swine Field Specialist, Iowa State University - Over the years, several people have requested information or specific suggestions on the temperature they should maintain their building for a certain pig weight or age.

My general response “let the pigs tell you.” The fact is that there is not a specific temperature that is appropriate for all building designs. The intent of this paper is to give a brief overview of ventilation factors and principles that may help you establish the appropriate effective environment for pigs in your operation or specifically your buildings. Different set points may be appropriate for different building type, ventilation system, and season changes within the same operation.

Energy Exchange – four basic methods:

  • Conduction – transfer of heat by physical contact with another surface. Ex: floor, walls, etc.
  • Convection – transfer of heat by physical contact with air, mud or water. Ex: Cold daft – negative, but positive when cooling.
  • Radiation – heat transfer as result of “radiatively seeing” surface temps that differs from the pigs surface. Ex: Stand next to a large window, in winter it is feels colder, while in summer feels warmer than the air temp of the room.
  • Evaporation – heat transfer as result of water conversion to a vapor. Ex: Breathing – water evaporation in respiratory tract and useful in cooling systems such as sprinklers and drippers.
Assessing the Thermal Environment:
  • Air Temperature – thermometers; affects convection, and evaporation
  • Speed of Air Moving over the pigs – smoke (stick, bag,etc.), digital, paddlewheel sensors; affects convection and evaporation
  • Surface Temperatures – infrared thermometer; affects conduction and radiation
  • Relative Humidity – hygrometer; affects convection and evaporation
Add them up = EFFECTIVE ENVIRONMENTAL TEMPERATURE (EET)


The pig has a core temperature of approximately 103 oF. Biologically, the pig will “do what ever it takes” to maintain a constant core temperature. The adaptive abilities are extensive, yet are limited. If the thermal environment is cold, the pig responds by huddling, shivering, redirecting blood flow to the core or excessively eating because too much thermal energy is lost to the environment. In hot environments the pig may pant, lie spread out on cool floors, wallow in mud and suppress eating.

The presentation of Effective Environmental Temperature is to stress that more than just air temperature affect what the pig effectively is feeling. Consider you are in a room that the air temperature is 76 oF - sitting on a chair you are comfortable; however, sitting directly on a block of ice you may get cold.

Lower Critical Temperature (LCT) is accepted as the effective temperature of the environment where pigs will need to consume more feed and apply extraordinary measures to keep warm. Likewise, the Upper Critical Temperature (UCT) is where pigs decrease feed consumption and apply extraordinary measures to keep cool.

Studies have shown for every 1 oF below the optimum effective temperature pigs under 60 lbs. need to consume 0.015 lbs/day more feed and pigs greater than 80 lbs. need to consume 0.044 lbs/day more feed to supply the extra energy that is being lost to the pig’s surrounding. In our confinement building this may be caused by low air temperature and/or a draft and/or wet flooring.

Studies have also shown for every 5 Lower oF below the optimum effective temperature pigs may have a 10-15% reduction in feed intake and a 10-15% reduction in average daily gain.

The following graph represents the LCT, UCT and optimal effective temperature range.


When zonal heating is provided to adequately accommodate a group of pigs, room air temperature can be reduced. Management is still the key to adjust the pigs effective temperature. Avoid “fire & ice” whereby zonal heat on the pad is too hot for pigs to lay on, yet the greater pen is too cold so pigs pile. Pigs piling indicates too low of effective temperature!

The ventilation system is the tool to provide the pigs with the appropriate effective environment temperature. The following are calculations to ensure enough capacity is provided and can be managed.

Suggested ventilation goals: Humidity: 50 to 70%; Inlet air speed: 800 to 1,000 ft/min; Static pressure: .05 to .10 inches


Be critical of potential drafts from air inlets, door ways and in winter, unused summer fans leaking. Ensure that enough air inlet area is provided – too few inlets or too many shut off will increase the speed of air entering and may cause drafts. Leaving a door open in summer will “short-circuit” the system and actually increase effective temperature by reducing airspeed. Observe influence of lights, feed and water line on air current if placed in front of inlet air. Ensure enough attic intake area is provided – protective covering with 3/8” holes. House soffit covering is too restrictive and can plug easily with dust or snow, thus increase the static pressure in the building.

Management considerations: Humidity – too high, increase ventilation or increase heat; too low, reduce ventilation. Ammonia – too high, remove manure more frequently, clean more thoroughly, add water to gutters, increase ventilation. Carbon Monoxide – too high, clean & adjust gas heaters, prevent backdraft of exhaust, increase ventilation rate. Dust – clean more frequently, increase humidity, upgrade/repair feed system (drop tubes, feeder adjustment, feeder lids, wet/dry feeders), add fat (1-2%) to diet.

While you can establish a set plan to operate a building – do not expect to use the same approach on all of your buildings if they have different equipment or different ages …. with similar settings, they can provide the pigs a different Effective Environmental Temperature. Let the pigs guide you to fine-tune your ventilation settings.

August 2006