In this study, controlled-chamber experiments were carried out to develop an operant mechanism that allowed the sows to demonstrate their preferred environmental temperature and to study the effects of fibre addition on growth performance and physiological response. Results showed that sows fed with high heat-increment diet were able to maintain significantly lower temperatures over the 24-hr period than those fed with standard gestation diet. Performance and physiological responses of sows fed with high heat increment diet seemed to have not been affected by the exposure to colder temperatures. Subsequently, the developed operant mechanism and the use of high heat-increment diet were implemented in an actual gestation barn with group-housed sows and results showed that sows could tolerate temperature 8°C colder than the current set-point (16.5°C) maintained in most gestation barns without adversely affecting their growth performance and physiological response as well as their behaviour and welfare. Lower temperatures maintained in the Sow-controlled room resulted to about 59% reduction in energy cost for heating and ventilation.
