Cost of Transport as a Discriminator of Conditioning in Horses Submitted to Incremental Jumping Tests

Cost of transport, but not gluteus medius and red blood cells monocarboxylate-transporters density differentiated Brazilian Sport Horses at two performance levels

Cost of transport (COT) and monocarboxylate transporters (MCTs) could affect the ability to perform fast actions during a jumping discipline. This study aimed to compare the COT and evaluate the MCT1, MCT4, and their auxiliary protein CD147 content in the gluteus medius and RBCs of Brazilian sport horses (BH), a breed developed for jumping competitions, with low-level (LL) or intermediate-level (IL) jumping capacities. The physiological difference between the horses was assessed by an incremental jump test (IJT), in which the cost of lactate (COT_LAC) and heart rate (COT_HR) of running were determined for each animal by the ratio between each variable and the running speed. Western blotting was performed on muscle and RBC membranes to quantify MCT1, MCT4, and CD147. IL showed lower COT_LAC and COT_HR than LL at all jumping heights. The amount of MCT1, MCT4, and CD147 found in muscle and RBCs were not dependent on performance level. Muscle MCT4 and MCT1 were correlated positively with CD147. We conclude that the relatively small differences between performances did not relevantly influence MCT expression in BH. While MCT analyses are inaccessible for most trainers and veterinarians, the cost of transport measurements is a feasible and sensitive tool to distinguish intermediate and low-level jumping horses.

Comparison between specific and nonspecific tests for evaluating the physical fitness of show jumping horses

Show jumping is a century-old Olympic sport performed worldwide. However, despite the prominence of this sport, there is currently no satisfactory evaluation of the physical fitness of its horses. Our study compared two standardised exercise tests (specific and nonspecific for show jumpers) to determine the importance of a show jumping specific evaluation test. Sixteen horses were divided into two performance groups (high and low performance), and all horses performed standardised exercise tests without jumps (SET1) and with jumps (SET2). Heart rate, blood lactate, glucose, blood gas, haematological parameters, and plasma ions were measured before and after the tests, and performance indices were calculated. Both exercise tests (SET1 and SET2) resulted in changes in nearly all measured variables that were expected, based on other studies, for the duration and nature of the exercise performed. Differences between the two performance groups were observed for lactate and glucose, as well as some blood gas variables and performance indicators. These differences might have been the result of better cardiovascular and metabolic adaptation of the high performance group to the show jumping exercises. For the SET1, differences between groups were mainly noted for variables related to aerobic capacity, which suggests that this measurement is important for the evaluation of equine performance in show jumping. The SET2 was capable of detecting different horse performance levels that could not be detected by the SET1, which indicates that a specific test for show jumping (that includes jumping movements) could provide important information for the evaluation of show jumpers. Based on our findings, we recommend that the SET2 be included in future protocols for evaluating jumping horses.