Rather too cold than too warm
Pigs only have sweat glands on their snout and are incapable of regulating their body temperature through perspiration. This makes them sensitive to high temperatures, and even small temperature increases will cause behavioural changes. A Dutch study from 2005* showed changes in behaviour and physiology in a group of 60 kg finishers.
The finishers were kept in a pen with 40% slatted floors and 60% solid floor surface. The following behavioural changes were observed:
- Wallowing behaviour
The first behavioural change in the pigs was that they cooled down by wallowing
in manure. This behaviour 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 step with more and more pigs resting on the slatted floor, pigs use the solid floor
surface for dunging, thus "reversing" the pen. This behaviour started at a house
temperature of 20°C.
Increased breathing frequency
The first physical change occurred at a house temperature of 22-23°C, when the
breathing frequency of the pigs increased.
Reduced feed intake and increased body temperature
When 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.