Effects of somatotropin and training on indices of exercise capacity in Standardbreds.

The research article investigates the effects of equine somatotropin (eST) and training on the exercise capacity of maturing Standardbred horses. Despite the hypothesized effectiveness of eST in improving horse exercise capacity, the study found no significant impact. However, the study noted marked improvements in the horses’ fitness indices due to the training program applied.

Study Context and Objectives

• The research was sparked by the recent availability of recombinant equine somatotropin (eST), a hormone believed to have potential ergogenic aid in horses, raising concerns about its use.
• The objective of the study was to understand the changes in exercise capacity in maturing horses undergoing a training program and to gauge the effectiveness of eST as an enhancer to this exercise capacity.
• The hypothesis tested was if the combination of training and eST is more beneficial to improve exercise capacity than training alone due to the anabolic effects of ST and its potential to boost cardiac function, circulating fluid volume, and red cell mass.

Methodology

• Twelve untrained Standardbred horses of about 20.7 months were used for the study and were paired according to their bodyweight. They were then arbitrarily assigned to the treatment or control group.
• The horses underwent a 12-week treadmill training program. Methionyl eST was given to the horses in the treatment group for 42 days during the 12 weeks.
• All horses performed a standard maximal exercise test to fatigue at the beginning, and then every three weeks till the end of the 12 weeks. During these tests, parameters like VO2, VCO2, plasma lactate concentrations ([La]), heart rates, blood volume, and total run time were measured.

Findings and Conclusions

• The study found no significant effect of eST administration on various indicators of exercise capacity such as VO2max, V200, V(LA4), LA9, red cell volume (RCV), plasma volume (PV), or run time to fatigue.
• From the starting to the concluding weeks of the program, training significantly altered certain indices – VO2max, V(LA4), LA9, RCV, PV, and run time to fatigue – indicating improved fitness in the horses.
• The conclusion drawn was that eST administration does not significantly improve the exercise capacity or fitness indices of young Standardbred horses in training. However, the maturing horses did show a rapid physiological response to training exercise.
• The researchers suggest further studies on the relationship between exercise capacity and ST in horses given these findings.