Decoding Holstein-Friesian dairy cattle vocalisations: Applications for welfare assessment

Abstract

The information encoded in cattle vocalisations remains underexplored. The objective of this thesis is to provide fundamental knowledge on the vocal behaviour of Holstein-Friesian cows exhibited during a variety of free-ranging and commercial dairy farming contexts. This thesis commenced with a literature review of previous cattle bioacoustics studies (Chapter 2) and highlighted the benefits of adopting the human-derived source-filter theory and arousal-valence dimensional framework for deciphering vocal information content. The experiment provided as Chapter 3 revealed that heifers have individually distinct voices, with different source and nonlinear parameters contributing to this distinctiveness. This work is also the first to show that heifer vocal individuality is maintained across putatively positive and negative farming contexts. Chapter 4 observed cow vocalisations during parturition and calf separation, uncovering context-related variation in the spectrographic vocal features and underlying phonatory gestures of the cows. Chapter 5 further showed that a disruption to cow and calf contact can lead to temporal modulations in the organisation of vocal, maternal and stress responses in cows. The vocal features observed in Chapters 4 and 5 varied depending on the signal receiver as well as distance over which communication occurred. These features also likely reflected emotional or motivational differences in the peri-partum cows. This thesis enhances our understanding of the static and dynamic information content of cattle vocalisations and demonstrates the feasibility of assessing certain vocal parameters in the commercial farming environment, where the soundscape is uncontrolled. It may also encourage farming practices to be shaped according to the vocal feedback of cows and highlights the opportunity to vocally assess cow welfare by visual and aural means.