Assessing Respiratory Pattern Changes Using a Microphone at High-Speed Trot in Standardbred Trotters – a Pilot Study: Abstract LT2

Horses are exceptional athletes with high respiratory capacities. Despite this, the respiratory system can become a limiting factor for equine performance resulting in compromised equine welfare when unnoticed. This becomes particularly relevant for horses used in sports that require great speed and/or stamina. Measuring respiratory rate (RR) during exercise is challenging due to practicalities and motion artifacts. Studies have used average RR as an outcome measure, without looking at how it may change during training. More detailed information on RR and breathing patterns can help to understand the horse’s workload, adaptation to training and to identify possible respiratory pathologies. The aim of this pilot study was to determine RR and to further explore parameters associated with the breathing patterns of standardbred warmblood trotters at high-speed trot, and whether this changes during a training session. Thirteen standardbred warmblood trotters were equipped with an omni-directional microphone (ECM-LV1, Sony, 44100 Hz), voice recorder (ICD-PX470, Sony) and a GNSS node to collect speed. The voice recorder was attached to the cheek piece of the bridle and the microphone was placed near the nostrils. Data were collected during a standardized exercise test with high-speed trot being the focus for this pilot. All horses were in active training and driven on an oval track with a sulky. High-speed segments were identified, and expiration events were manually labelled based on sound and audio graphs. The 50%-duration mark was identified creating a first and second half used for analysis. Statistical analysis was performed using Linear Mixed Models (fixed-effect = ‘segment’, random-effect = ‘horse’, α=0.05). Average speed was 36.9±6.2 km/h. The RR was higher in the first half of the segment compared to the second half (106±4 resp. 101±4 breaths/minute, p=0.03), with average RR values ranging from 73 to 127 breaths/minute. Breathing out duration differed with 0.15±0.01 and 0.18±0.01 seconds for the first and second half of the segment (p<0.001). Initial observations showed inter-individual differences in breathing sounds and regularity of ins-/expiration. Some horses showed very regular breathing patterns (i.e., in-out-in-out), whereas others sometimes skipped an expiration or inspiration. These results highlight the importance of studying respiratory behaviour more closely. Breathing patterns differ between horses and change within constant speeds at different points during training. Microphones can be non-invasive tools to monitor equine breathing during training sessions providing essential information on the response to training. Possible breathlessness or respiratory pathologies could be detected earlier, thus promoting equine welfare.