Heat stress assessment by swine related vocalizations

In intensive swine farms, stressful conditions in the climate, namely heat stress, affect animal behaviour and welfare. Pigs reared in commercial fattening housing suffer from temperature increases and from their inability to get free to refresh themselves any time they need to. The closed and dense environment further worsens this condition. This particular study was conducted to determine whether heat stress induces specific vocalisations in a group of piglets bred in standard intensive conditions and whether these vocalizations are acoustically different from other swine normal vocalizations. The temperature increase was aimed to stimulate heat-stress-specific behaviours and vocalisations. For this purpose, the vocal calls were coupled with environmental and physiological parameters (rectal temperature and respiration rate) collected during the temperature-increasing tests. The study of sound acoustic features such as frequency, duration and amplitude, together with the analysis of the environmental parameters, showed a clear difference between heat-stress-related sounds and other types of vocal calls recorded while the piglets were not stressed by environmental insults. This result shows how animals can communicate emitting specific calls and provides a deeper knowledge of animal behaviour, thereby providing a means toward better animal welfare.