Fig. 2. Cost of transport for a range of walking and trotting speeds (closed and open circles, respectively). Data are shown for the miniature (A–C), Arabian (D–F) and draft (G–I) horses. Dashed lines are least-squares second-order polynomial curve fits. Bars indicate the observed gait used continuously by the horse during the transition speed measurements. Hatched bars indicate speed range where the horses switched gaits at least once during the 1 min observation period. Horses were then trained to use a prescribed gait for oxygen consumption measurements at speeds within the hatched bar region after the transition speed measurements were completed. However, we were not able to obtain walking and trotting _O2 data at the same speeds in the transition region for the miniature and draft horses. In these cases, the curve fits were extended beyond the data as shown to calculate the optimal metabolic transition speed.