Field-applicable low-intensity exercise induces bronchodilation in horses with severe asthma.

BACKGROUND

Airway dysfunction in severe equine asthma (SEA) often results in early retirement or euthanasia of affected horses. Exercise-induced bronchodilation occurs in horses with SEA after intense treadmill exercise, but the effects of a lighter, field-applicable, training regimen remain largely unexplored.

OBJECTIVES

To evaluate the impact of submaximal aerobic exercise on airway obstruction during exacerbation of SEA.

STUDY

DESIGN

The preliminary phase explored the effects of a 25-min standardised exercise on the lung function of eight SEA horses. As notable bronchodilation occurred, the results were confirmed in a randomised controlled crossover protocol comparing the effect of the same standardised exercise on lung function with that of an equal duration turnout.

METHODS

Lung function was assessed by standard lung mechanics before and 15 min after the interventions (turnout and walk/trot lungeing exercise). To compare exercise-induced bronchodilation with that of a potent bronchodilator in the main study, salbutamol was administered after the turnout intervention only, and lung function was measured again 5 min later. Data were analysed with t tests, Wilcoxon tests, and mixed-effects models.

RESULTS

In the preliminary phase, exercise led to a mean 50% reduction in pulmonary resistance. This was confirmed in the main study, where pulmonary resistance decreased from 2.6 (2.1-3.3) to 1.3 cm (0.8-2.2) H2O/L/s after exercise (p = 0.006), whereas it remained unchanged after the turnout intervention. Following salbutamol administration after the turnout, lung function was comparable to that of the lunged horses, suggesting that the extent of exercise-induced bronchodilation was similar to that achieved with a β2-adrenergic agonist.

MAIN LIMITATIONS: The small number of aged horses, the lack of blinding, and the focus on the short-term effects of exercise restrict the generalisability of the results.

CONCLUSIONS

The rapid and potent bronchodilation achieved through brief aerobic exercise supports the investigation of a training program's impact on the management of SEA.