Vocal-type classification as a tool to identify stress in piglets under on-farm conditions

Abstract

Previous studies have shown that the analysis of high frequency stress calls in pigs can serve as a reliable tool in welfare research. Our study focuses on the classification of three different classes of piglet vocalisation: grunting, squealing and screaming. In a castration experiment (Experiment 1), 3,285 vocalisations from 42 piglets were analysed for 21 different vocal characteristics. A first discriminant function for the three vocal types was derived from recordings made under laboratory-like conditions. A second discriminant function was derived from non-calibrated measurements of the relative sound energy content. These two classifications revealed 86.7% identical assignments of vocalisations to the three vocal types. The second classification allowed for vocalisation analyses of animals under on-farm recording conditions. This technique was validated during an open-field test (Experiment 2) with piglets housed in two different farrowing systems (11,089 vocalisations, 22 piglets). The proportion of screaming sounds was lower for piglets from a group-farrowing (GF) system than for those from a single-farrowing (SF) system. Sound properties showed differences between as well as within the two experiments for all three vocal types. Vocalisations from SF and GF piglets differed significantly in the duration, energy, and relative maximum levels. We conclude that vocal-type analysis can not only help to identify vocalisation indicative of pain during castration, but also vocal behaviour changes indicating separation stress during the open-field test. Therefore, classification of vocal types can add valuable information to studies that use pig vocalisation for the assessment of welfare.

Opportunities for Regulatory Authorities to Assess Animal-Based Measures at the Slaughterhouse Using Sensor Technology and Artificial Intelligence: A Review

“…Measuring body weight and/or size in pigs using a camera has been studied extensively [144][145][146][147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162]. Automatic recording of vocalisations as a sign of fear, pain and stress as well [163][164][165][166][167][168][169][170][171][172][173][174][175]. Although, this are studies in an experimental setting and not on automatic recording of vocalisations at the slaughterhouse.…”

“…Aggressive behaviour [200][201][202][203][204][205][206] † Mounting [207][208][209][210][211][212] Fear Reluctance to move, freezing [213] [192,214] AI4Animals [178] Fear and pain High-pitched vocalisations [163][164][165][166][167][168][169][170][171][172][173][174][175] * are externally validated. † only sensors, no AI.…”