Reducing heat stress
Heating and supplemental energy conservation is the major concern in cold climate swine housing.
But summer heat stress also presents a serious challenge to prairie pork producers, especially in those buildings with attic air inlet
systems.
Pig barns with attic air inlet systems (by far the most common system now in place) should be able to maintain the room temperature within two degrees Celsius of the outside air. This allowance is often exceeded because of errors in design, construction or ventilation management.
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Of all farm animals, pigs are most susceptible to heat stress. They have limited ability to sweat, subcutaneous fat deposits impair heat transfer and panting – respiratory response to heat stress – is limited. Pigs are affected by high temperatures much more than cattle. Performance quickly decreases under heat stress.
Heat stress is likely a more significant problem for pork producers on the Prairies than most would expect. For example, growth rate of a finisher pig decreases three percent for every one degree temperature increases above 20 C.
A preliminary study at the Prairie Swine Centre in Saskatoon during the summer of 1994 showed attic heating by solar radiation could reach seven degrees above the outside air.
The average heating load was
3.7 C for 78 percent of the time during July and August for grower/finisher pigs.
In another study, summer growth rates as low as 777 grams per day have been observed, compared to the overall barn average of 850 g per day for winter production cycles.
Heat stress is not as easily observed as cold stress in pigs. When pigs are cold, they huddle together. When pigs are hot, they eat less and grow slower. Heat stress also impairs animal welfare. When a room is too hot, pigs are likely rolling in manure to cool themselves and make the pen dirty, behavior that facilitates the spread of disease.
Tips for reducing heat stress:
- Follow the space requirement. Move pigs if the room is overpopulated. Ventilation systems are designed for a given number of animals. Overpopulation of animals will exceed the ventilation capacity.
- Set the room temperature low and reduce the temperature differential for multistage ventilation fans. A low temperature setpoint and a small interstage temperature differential allow the ventilation system to achieve its full capacity before heat stress occurs. Follow the recommended temperature setpoints.
- Check there is enough fan capacity for summer ventilation.
- Ensure the opening area for air inlets is adequate. This is especially important for airtight buildings.
- Use a cooling technology such as water sprinkling to reduce the heat stress. Evaporative cooling can reduce the ambient temperature by two to three degrees.
– Prairie Swine Centre
