HOUSING
PIH-87
pork industry handbook
PURDUE UNIVERSITY COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, INDIANA
Cooling Swine
Authors
Don D. Jones, Purdue University
L. Bynum Driggers, North Carolina State University
Robert L. Fehr, University of Kentucky
Reviewers
Gerald Gehlbach, Lincoln, Illinois
Albert J. Heber, Kansas State University
Howard Person, Michigan State University
Russell and Janet Roberson, Devina, Texas
Hot weather reduces swine performance more than cold weather, resulting in significant economic loss to the pork producer. This occurs because buildings in much of the United States are designed for cold weather while producers often are content to “wait out” hot spells. Hot weather usually does not result in death losses, but it can cause conception problems and subtle reductions in feed intake that result in significant drops in production. Reduced sow feed intake also can affect baby pig performance.

The purpose of this publication is to suggest practices which minimize animal production losses through the use of effective, energy-efficient cooling systems. Discussed first are the ways in which pigs give off excess body heat. This is followed by a discussion of the various types of cooling systems based on heat dissipation principles. The information provides a basis for evaluating your present system or selecting one that best fits your situation.

Heat Dissipation
Larger pigs (animals in gestation, farrowing, breeding and finishing phases of production) begin to feel the effects of heat stress at about 70°F. If temperatures remain above 85 °F for more than a short period of time, substantial losses in performance and in reproductive efficiency can result unless some type of cooling relief is provided. Pigs dissipate little moisture through their skin-certainly not enough to rid themselves of excess body heat. Therefore, to relieve heat stress, they must depend upon heat dissipation to their environment in one or more of the following ways: convection, conduction, radiation, or evaporation through the respiratory tract (panting). Evaporative cooling from the body surface also is possible if some type of artificial surface wetting is provided along with adequate air movement over the animals.
Convection
Convection heat loss results from air movement over the animal’s body. This is an effective means of cooling, provided two conditions are met: (1) the air velocity is at least 2 mph, and (2) the air temperature remains at least 10°F below the animal’s body temperature (102 ± 1°F). At air temperatures in the range of 80°F to 95°F, pigs can dissipate up to 30% of their body heat by convection to the surrounding air.

Conduction
Conduction heat loss occurs when the animal’s skin is in direct contact with a cooler surface. Conduction usually accounts for only 5% to 10% of the total heat loss in hot weather, because temperature differences are small and only about 20% of the animal’s skin is in contact with the floor surface, even less if the floor is slotted.

Conductive heat loss to the cool ground surface under a shade in a pasture or a lot can be significant. However, it is not as important in concrete-floored buildings, because higher building insulation levels and a greater concentration of animals maintain a warmer floor surface temperature. Insulation placed under the floor or along the foundation specifically to control winter heat loss further reduces summer conductive cooling.

Radiation
The surface of an animal’s skin is constantly radiating heat to or receiving radiant heat from its surroundings. Where the surrounding wall, ceiling and floor surfaces are cooler than the skin, there will be a net loss of heat from the animal, making it feel cooler. Radiant heat loss is directly related to the insulation level of the building. Insulation keeps inside building surfaces cool in the summer, especially the roof or ceiling. Radiation typically accounts for about 20% of the total animal heat loss in the
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture cooperating. H. A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age, or handicap.