Rather too cold
than too warm
Pigs only have sweat glands on their snout and are incapable of regulating their body temperature through perspiration. It makes them sensitive to high temperatures, and even small temperature increases cause behavioral changes. A Dutch study from 2005* showed changes in behavior and physiology in a group of 60 kg finishers.
The finishers were kept in a pen with 40% slatted floor and 60% solid floor surface. The following behavioral changes were observed:
The first behavioral change of the pigs was that they cooled down by wallowing in manure. The behavior was observed already from 16-17°C.
Changing resting area
At 19°C, the pigs started resting on the slatted floor, as this is cooler than the solid floor surface, and the air velocity around the slats is higher.
In steps with more and more pigs resting on the slatted floor, pigs use the solid floor surface for dunging, thus reversing the pen. The behavior started at a house temperature of 20°C.
Increased breathing frequency
The first physical change occurred at a house temperature of 22-23°C; the breathing frequency of the pigs increased.
Reduced feed intake and increased body temperature
When the house temperature rose to 25-26 °C, the pigs' feed intake decreased and their body temperature increased.
*Huynh, T.T.T., A.J.A. Aarnink & M.W.A.Verstegen, 2005. Reaction of Pigs to a Hot
Environment. Livestock Environment VII. Proceedings of the Seventh International
Symposium, Beijing, China.