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

This research investigated the relationship between the performance of Brazilian sports horses in jumping disciplines and their cost of transport (energy expenditure). It was found that while there was no clear link with certain transporter proteins in muscles and red blood cells, the cost of transport was a valuable tool for discerning performance levels.

Overview of the Study

• The study was aimed at comparing the cost of transport (energy expenditure during activity) and examining the content of monocarboxylate transporters (proteins that transport lactate and other molecules) in the muscles and red blood cells of Brazilian sport horses. These horses are primarily bred for jumping competitions.
• The horses in the study were grouped into two performance levels: low-level (LL) and intermediate-level (IL).
• The physiological differences between the horses were evaluated using an incremental jump test, which measured lactate cost of transport and heart rate cost of transport, by calculating a ratio of these variables over running speed.

Key Findings

• The study found that the intermediate-level horses demonstrated lower costs of transport at all given jumping heights, compared to the lower-level group.
• This indicates that more efficient horses use less energy to perform the same task, highlighting the cost of transport as an important differential metric.
• However, no significant impact was observed on the expression of monocarboxylate transporters (MCT1 and MCT4) and the auxiliary protein CD147 in muscle and red blood cell membranes, based on performance levels. This implies that performance level does not drastically influence the transporter protein content.
• A positive correlation was observed between the levels of MCT4 and MCT1 transporters with CD147 protein, suggesting a possible cooperative function.

Conclusion and Implications

• Despite minor differences in performance, the study concluded that there wasn’t a significantly influential effect on the expression of MCTs in Brazilian sport horses.
• The study emphasizes that cost of transport measurements stand as a feasible and sensitive tool to distinguish between intermediate and low-level jumping horses.
• This conclusion carries practical implications, stating that while analysis of MCT levels may be inaccessible for most trainers and veterinarians due to complex procedures, the cost of transport provides an easier, effective method to assess horse performance.