Chronic recombinant equine somatotropin (eST) administration does not affect aerobic capacity or exercise performance in geriatric mares.

This research aimed to determine if the long-term use of equine somatotropin (eST) could enhance the aerobic capacity and exercise performance of older mares. The study found no significant positive effects of the eST treatment on the mares’ physical capacities.

Research Design and Methodology

The study investigated the impact of long-term (89 days) administration of eST on 15 healthy, unfit, aged mares (20-26 years old). These mares were randomly divided into two groups: one group was given the eST treatment (12.5 mg per day) while the other served as a control group receiving a placebo treatment.

• The mares’ aerobic capacity and exercise performance were measured using a high-speed treadmill with a standard exercise test (SET). The SET started with the mares running at a steady speed of 4 m/s up a fixed 6% incline, with an increase in speed of 1 m/s every 60 seconds.
• The resting data were collected, and oxygen uptake (VO2) was measured using an open flow calorimeter. Blood lactate concentration (LA) was identified with a lactate analyser.
• Venous blood samples were taken before, during, and after the exercises to evaluate other relevant variables — LA, plasma protein concentration (PP), hematocrit (HCT), and the plasma concentrations of creatine kinase (CK) and aspartamine transferase (AST).

Key Findings

Upon analyzing the data, it was found that there were no significant differences in any of the measured parameters as a result of the eST treatment.

• Resting VO2, LA, TPP, or HCT remained consistent regardless of whether the mares were in the treatment or control group.
• In addition to the resting conditions, the maximal oxygen uptake (VO2max), top run velocity, run time, watts at VO2max, velocity to achieve a lactate of 4 mmoll-1 (VLA4), watts at weight loss or peak HCT, and peak LA all remained the same.
• Lastly, there were no discernible differences in CK or AST, be it before or after exercises. These two enzymes may indicate muscle tissue damage, so the consistent levels further prove that the eST treatment isn’t significantly beneficial or detrimental.

Conclusion

Based on the findings of this study, it can be concluded that chronic eST administration does not improve the aerobic capacity or exercise performance of unfit aged mares. Further research may be needed to explore any potential benefits of eST under different circumstances.