Effect of inhaled beta 2 adrenoceptor agonist, albuterol sulphate, on performance of horses.

This research study investigates if an asthma medication, albuterol sulphate, improves the performance of thoroughbred horses during increasingly intense exercise. The study found a small but significant increase in both exercise duration and peak oxygen consumption in horses treated with the medication.

Hypothesis and Experimental Design

• The study intended to examine whether the use of albuterol sulphate, a drug that stimulates the beta 2 adrenergic receptor, could influence the exercise performance of Thoroughbred horses.
• The researchers employed a double-blind, crossover design where six conditioned horses were randomly assigned to two groups. Group one was given a placebo, while group two received albuterol sulphate. After a three-week gap, the treatments were swapped to ensure data reliability.

Procedure and Measurements

• Horses were administered albuterol or placebo over five minutes, followed by an exercise test that gradually increased in intensity until reaching peak oxygen consumption (VO2peak).
• Data regarding facial arterial blood gases (PaO2, PaCO2), pH level in blood (pHa), temperature, and electrolytes were recorded. The study also monitored substances in the blood that can indicate oxygen transport and metabolism: O2Hb, COHb, MetHb, and RHb.
• Other critical factors, such as heart rate, CO2 production (VCO2), blood lactate levels, speed at the point of failure, exercise duration and levels of albuterol and its metabolites in the urine, were also tracked.
• Continuous arterial blood gas data was provided by a Paratrend7 intravascular sensor.
• Data was analysed using mixed-effects linear modelling with generalised least-squares estimation to look for interactions between treatment and speed.

Results

• The study found significant differences between the placebo and albuterol-treated horses in total run time and the run time from the completion of 8 m/s until fatigue. Albuterol-treated horses ran for longer durations on average.
• Additionally, peak oxygen consumption (VO2peak), a measurement indicative of aerobic capacity and endurance, was higher in horses treated with albuterol compared to those given a placebo.

Conclusion

• The study concluded that inhaled albuterol sulphate might slightly enhance the performance of Thoroughbred horses during incremental, peak oxygen consumption exercise tests. This improvement was manifested in higher VO2peak and longer run times for the horses receiving the drug treatment.