Heart rate responses of two breeds of four-gaited horses to a standardised field gaited test

In order to understand how gaited horses use their energy during exercise, a standardised field gaited test (SFGT) was developed to assess energy expenditure of four beat gaited horses independently of size, sex or breed. This work aimed at developing such an SFGT, using as main measurement parameter the heart rate (HR) of horses during the SFGT performance. Thirty-one four beat gaited horses were evaluated and divided into two groups: FIT (conditioned) and UNFIT (not conditioned). Horses were submitted to the SFGT and their heart rates were measured with a heart rate monitor as follows: right after being mounted, at the beginning of pre-test (HRSADDLE); at 5, 10, 15, 20, 25 and 30 minutes of four beat gait dislocation; and at 15 minutes after the recovery period (T₊₁₅). Maximum HR (HR_MAX); HR percentage over 150 beats per minute (HR_{% > 150}), HR percentage over 170 beats per minute (HR_{% > 170}), and average HR during the four beat gait stage (HR_M@M) of SFGT were calculated. Results were analysed by ANOVA for repeated measures. Where significant differences were observed, 'T' test was performed and significance was set at 5%. The FIT group presented HR_MAX, HR₊₁₅, HR_M@M, HR_{% > 150} and HR_{% > 170} rates lower (P < 0.05) than the UNFIT group. It was noted that there was a negative correlation between fitness and HR_MAX (R=-0.67; P < 0.001) and a positive correlation between HR_MAX and HR₊₁₅ (R=0.60; P < 0.001) when comparing the FIT to the UNFIT horses. In conclusion, during the SFGT, the FIT group was more efficient in energy expenditure than the UNFIT group, based on the results observed for the significantly lower HRs during the SFGT. It is relevant to note that the SFGT developed and used in this research, which was easily reproduced and accurate, was able to detect and confirm important adaptations related to fitness in the athletic horse.