Engineers at the Prairie Swine Centre in Saskatchewan, Canada have found an easy way to keep hogs cooler without adding to production costs.

Cooler pigs grow 5% faster, which decreases marketing time by 3-5 days and improves net profit by 75¢/pig sold, estimates Stephane Lemay, research engineer.

On warm days, temperatures rise outside the barn. For a while, the barn stays cool. But eventually the attic temperature rises and the outside heated air is brought into the room.

“During the warm months of spring and summer, we typically see room temperatures rise above outside temperatures,” notes Lemay. “It is expected to find room temperatures three degrees above outside temperatures, and with some barn designs, temperatures can rise even further.”

Heat stress strikes when temperature, humidity and ventilation rates combine to produce temperatures above the animals' comfort zone. This depresses appetite, reduces gains and delays marketing.

The level of severity is weight-related, he says. Younger pigs tolerate higher temperatures better.

Table 1 illustrates temperatures set for various categories of pigs. Lemay says for each one-degree rise in temperature above the pig's comfort zone, feed intake will decline by 1-2% and growth rate by 3%.

For every degree in temperature above the pig's comfort or thermoneutral zone, net income is reduced by 30 cents to 45¢ /pig.

Setting the ventilation controller six degrees below the recommended temperature creates a cool nighttime environment.

“The pigs become more active in the cool evening as we would expect,” says Lemay. “Their first inclination is to go and eat.

“This cooling period effectively reduced the overall impact of high temperatures on the pig performance each day and reduced the nighttime temperatures by about two degrees below the control rooms.”

Researcher: Stephane Lemay may be reached at (418) 286-3551 or

Study Boosts Biofilter Efficiency

Biofilters drastically cut hog odors from confinement units. But University of Illinois (U of I) research suggests the effectiveness of biofilters can be improved by the choice of materials used and by maintaining an appropriate moisture level in the filter.

A biofilter is a bed of wood chips or other organic material attached to a confinement building's ventilation system or manure storage area with air ducts. Exhaust fans force air from the building or manure storage area through organic material. Bacteria and fungi growth remove odorous agents by using them for food. To work properly, the organic material must remain moist or the organisms will die off.

In U of I Ted Funk's research, two biofilters were tested to reduce odors from an in-ground manure tank on a western Illinois farm. One filter used a debarking product (tree bark and dirt) and the other used wood chips and hay.

Air samples from each biofilter were collected and sent to Iowa State University. An olfactory team of eight trained “sniffers” rated the overall odor strength of each sample.

“The debarking product worked better than the wood chips and hay to reduce ammonia,” reports Funk. “However, both media were pretty effective in odor reduction.

“The established method to monitor moisture content in the filter is to reach your hand in, grab a sample and see if it feels all right,” explains Funk. “It's kind of hard to get farmers excited about doing that.”

So Funk developed an automatic system to control moisture content.

“We wanted to produce a moisture-sensing technique that would give a readout of the moisture percentage in the filter,” he says, “and also trigger an electronic control to turn water on and re-wet the filter when it needs it.”

He built a three-grid capacitor that is buried in the biofilter medium. “When the moisture reading goes down to a certain level, the control circuit triggers a switch to turn the water on. The reading goes back up and the process repeats itself, irrigating the biofilter as needed.”

Now Funk is working to make the invention cost-effective for the average producer.

Researcher: Ted Funk, University of Illinois. Phone Funk at (217) 333-9313 or e-mail

Table 1. Setpoint Temperatures (°F) for Swine During the Cooling Season
Room and Body Mass, lb. Solid Floor Slotted Floor Solid Floor with Straw
Dry Sows 66 70 64
Nursing Sow 64 68 63
Weanling 15 lb. 81 84 79
44 lb. 75 79 72
Grower-finisher (continuous)
55-132 lb. 66 70 64
132-220 lb. 61 63 59
55-220 lb. 66 70 64
(All-in all-out)
55 lb. 72 75 72
99 lb. 63 64 61
198 lb. 61 63 59
Source: Swine Building Ventilation - A Guide for Confinement Swine Housing in Cold Climates, Prairie Swine Centre Inc., 1994