The influence of challenging objects and horse-rider matching on heart rate, heart rate variability and behavioural score in riding horses.

A good horse-rider 'match' is important in the context of equine welfare. To quantify the influence of repetition and horse-rider matching on the stress of horses encountering challenging objects, 16 Warmblood horses were ridden in a test-setting on three occasions. On each occasion the horse was ridden by a different rider and was challenged by three objects (A-C). Heart rate (HR), heart rate variability (HRV) of horse and rider, and behaviour score (BS) of the horse were obtained for each object and as a total for each test. The horse-rider interaction was evaluated with each combination and assessed as 'matching' or 'mismatching', and the horses were categorised as 'compliant', 'partly-compliant' or 'non-compliant'. Horses exhibited a decreased HR (P=0.015) and a decreased BS (P=0.004) within and across different tests. 'Matching' horse-rider combinations exhibited less stress as indicated by reduced HR ('match' 69±10 vs. 'mismatch' 72±9, P=0.001) and BS ('match' 1.9±1.1 vs. 'mismatch' 3.8±1.4, P=0.017) of the horse. 'Compliant' (68±8, P<0.001) and 'partly-compliant' (71±9, P=0.002) horses had significantly lower HR than 'non-compliant' (75±9) animals. The findings of the study indicate that HR and BS measurements support a subjective 'match' diagnosis and HR measurement may be a valuable tool in assessing horse compliance.