Pigs in confinement find it difficult to lose body heat. Therefore their well being is strongly dependent on the ambient temperature. Huynh discovered that they huddled less at a temperature above 16 degrees Celsius. At a temperature of about 19 degrees the animals sought a slatted floor to lie on. They also wallowed in urine and became less active.
If the temperature rises further, the pigs increase their breathing rate and eat less. Finally their body temperature rises. Thuy Huynh discovered that a high temperature, especially in combination with a high relative humidity, results in a poor growth of the pigs.
Reducing heat stress Providing the pig house with extra cooling in addition to the standard ventilation decreases the heat stress experienced by the pigs. Cooling the floor of the lying area, providing a water bath to bathe in, or regularly spraying water from a sprinkling installation cools down the overheated pigs. As a result of this their feed intake and therefore their growth rate increases.
Pigs are highly sensitive to the ambient temperature. They cannot actively sweat and the evaporation of water from the lungs is also limited. Rapidly-growing domestic pigs also produce more body heat than their wild relatives. Moreover, the fact that they are often kept close together in the pens only exacerbates this problem.
Thuy Huynh's research was financed by the Netherlands Organisation for Scientific Research (NWO).