Responses of slaughter pigs to transport and lairage sounds

The behavioral and physiological responses of pigs to transport and subsequent exposure to slaughterhouse sounds were examined. Forty-one groups of four slaughter pigs were separately loaded onto a lorry and transported for 25 min. Another 43 groups were loaded onto the lorry which then remained stationary for 25 min. Following unloading pigs were moved to a race with a length of 15 m and a width of 1.5 m. Either one of the following sounds was played at 85 dB(A) for 10 min: Pigs in front of the restrainer, Machines in lairage, White Noise, or Control (no sound). Pigs exposed to the Machines and White Noise treatment spent significantly more time close to their group-mates compared with Control pigs, with pigs subjected to the Pig sound being intermediate. Transported pigs spent less time exploring the race and were less active than pigs from the stationary lorry. Heart rate was higher during transport than during the stationary period. In contrast, during unloading, the sound exposure period and the post-sound period, heart rate was lower in the transported groups. Heart rate did not significantly differ between sound treatments. Salivary cortisol concentrations were significantly higher after transport than after the stationary period and remained higher for transported pigs after the sound exposure period. Cortisol levels did not differ significantly between sound treatments. It is tentatively suggested that social support from conspecifics may protect pigs from potentially adverse effects of exposure to lairage sounds.