The Impact Of Auditory Stimulation On Equine Nocturnal Behaviour

Environmental enrichment (EE) can promote the display of biologically relevant behaviours within hypo- or hyper-stimulating environments, which can also aid in reducing stress. This study considered if nocturnal musical enrichment resulted in reduced frequency of alert behaviour and an increase in sleep-related behaviour for horses stabled overnight. Frequency of behaviour according to a pre-determined ethogram was recorded for seven horses (mixed sex/breed/height, age range 6 to 16 years) housed on the same yard and receiving the same daily management routine. Horses were observed over nine consecutive nights from 1900 to 0700 in their usual routine using focal continuous sampling and an infrared CCTV camera system. The first two nights established baseline nocturnal behavioural patterns (phase 1), followed by five nights where horses were exposed to Beethovens’ 9th Symphony played at an average of 62.3 decibels (phase 2). Two further non-consecutive nights of observation allowed behavioural data collection when music was no longer played (phase 3). The study gained ethical approval from the Hartpury Ethics Committee. Wilcoxon Signed Rank was used to determine differences in frequency of behaviour between pre-, with and post- music nights, whilst a Related-Samples t-Test was used to determine differences in frequency of behavioural switching between the three phases (significant at P<0.05). Frequency of ingestion was highest in phase 2, which was significantly different (Z=-2.46; P= 0.019) to phase 3, but not phase 1 (Z=-1.73; P=0.084). Frequency of locomotion significantly decreased from phase 1 to 2 (Z=-3.06; P=0.002) and remained low, with a significant difference noted between phase 1 and 3 (Z=-2.98; P=0.007). Generally, the frequency of lateral recumbency increased from phase 1<phase 2<phase 3 but no other significant differences were noted. Behavioural frequency remained relatively consistent during phase 2, with no significant differences between nights 3 and 7, although frequency of ingestion was observed to decrease while head over stable door increased. Behavioural switching occurred less frequently while music was played, and this was significantly different to both phase 1 (t=2.46; P=0.029) and phase 3 (t=-2.59; P=0.022). Music appears to result in longer behavioural bout duration, although curiosity appeared to increase towards the music stimulus during exposure to music. The addition of music appeared to reduce restlessness and encourage more biologically significant behaviours and might thus be considered useful in equine husbandry practices, for example to facilitate seasonal changes such as overnight turnout to stabling during the winter. Lay message: ‘Welfare of all animals in an indoor environment is of great importance and trying to improve that environment is an ongoing challenge. Little has been done to understand the nocturnal environment or how to enrich it. Music is known to influence horse behaviour and in this study the addition of music appeared to both reduce restlessness and be associated with the occurrence of biologically significant behaviours, for example sleep-related behaviour.’