A note on acoustic analysis of dairy calves’ vocalizations at 1 day after separation from dam

The vocalizations of animals are very useful in assessing an emotional state and welfare because they involve information about various emotions. Hence, the findings of the acoustic features of vocalization can be used to improve the productivity and welfare of animals. This study was conducted to analyse the vocalizations of dairy calves separated from the dam. At 6 days after birth, 12 dairy calves were moved into an individual calf pen (3.0mx2.0m) bedded with sawdust and straw. One and a half litres of whole milk were fed twice daily and free access to water was allowed. The calvesʹ vocalizations were divided into humming vocalizations (HVs: low continuous calls without tone changed), semi-humming vocalizations (SHVs: low continuous calls with tone changed), and general vocalizations (GVs). These vocalizations were classified, based on the shapes of waveforms and spectrograms. Differences in the duration, fundamental frequency, intensity, and formants among the classified vocalizations were found (P<0.0001). Acoustic parameters except intensity and 3rd formant were not different between HVs and SHVs. These results suggest that vocalization analysis could be a useful tool in assessing the emotions of calves. Acoustic parameters are also useful in classifying vocalizations. Also, intensity and 3rd formant are advantageous in distinguishing HVs and SHVs.