The use of pigs vocalisations structure to assess the quality of human-pig relationship

International audienceHuman voice is important for the development of piglets relationship with humans, and the quantity of vocalisations emitted by piglets in the presence of a human differs according to this relationship. Vocalisation structure is promising to assess pigs emotions and could encode the quality of human-pig relationship. This is what we tested here. Thirty piglets were tamed thanks to regular interactions with an experimenter talking and physically interacting with them, for two weeks three times a day from weaning; while 30 other piglets received only contact necessary for their good breeding. Two weeks later, we recorded their behaviour and vocalisations emitted in presence of the experimenter for five minutes. The test was reproduced two weeks later, after a period of conditioning using human presence and contacts as a reward for all piglets, supposed to lead to a positive human-piglet relationship for all piglets. Grunts structure was analysed and compared between tamed and untamed piglets, and before and after the conditioning period. Behavioural observations confirmed that taming lead to a positive attraction toward the experimenter in the test before the conditioning period. Grunts produced by tamed piglets were shorter than those produced by untamed piglets (means[se]: 305 [2.6] vs. 351 [3.9] ms, p0.05). This effect did not remain true after the conditioning. In conclusion, the structure (i.e. duration, dominant frequency) of pigs grunts is closely linked with the quality of human-pigs relationship. We confirm that vocalisations are a key indicator of pig welfare that should be used to assess it, and, more precisely they encode the quality of the perception of humans