Subclinical diseases underlying poor performance in endurance horses: diagnostic methods and predictive tests

Abstract

Thirty-eight endurance horses underwent clinical and ancillary examinations, including haematological and biochemical evaluation, standardised exercise tests both on a treadmill and in the field, Doppler echocardiography, impulse oscillometry, video endoscopy and collection of respiratory fluids. All of the examined poorly performing horses were affected by subclinical diseases, and most of them had multiple concomitant disorders. On the contrary, the well-performing horses were free of any subclinical disease. The most frequently diagnosed diseases were respiratory disorders, followed by musculoskeletal and cardiac problems. Poor performers exhibited lower speeds at blood lactate concentration of 4 mmol/l (VLA4) and at heart rates of 160 (V160) and 200 bpm (V200) on the treadmill and in the field, as well as slower recovery of heart rate.

Medidas ecocardiográficas de cavalos de tração da região metropolitana de Curitiba-PR

“…Na avaliação com Doppler colorido observouse regurgitação discreta em 36,85% dos cavalos avaliados, onde o maior número de animais tinha regurgitação na valva pulmonar, seguido pela valva aórtica. Fraipont et al (2011) observaram em cavalos de enduro regurgitação valvar que variou de leve a moderada, sendo a valva mais afetada a aórtica (41,9% dos cavalos com regurgitação) seguido pela pulmonar (22,6% dos cavalos com regurgitação) e mitral (22,6% dos cavalos com regurgitação). Os mesmos autores avaliaram a diminuição do desempenho de cavalos de enduro em relação à regurgitação valvar.…”

Inflammatory Airway Disease of Horses—Revised Consensus Statement

“…Racehorses and nonracehorses of all ages and from any breed/discipline can have IAD 14, 17, 24, 25, 26, 27, 28, 29. Clinical signs of IAD include decreased performance and chronic, intermittent cough 10, 12, 13, 23.…”

“…Signs like delayed recovery of respiratory rate after exercise and exaggerated respiratory effort during work,37 warrant further consideration. Impaired pulmonary gas exchange is a limiting factor to performance; intensely exercising horses with IAD exhibit worsening of exercise‐induced hypoxemia,33, 34, 38 and lower speeds of exercise are attained with blood lactate concentrations of 4 mmol/L26, 29; however, these variables are not specific for IAD.…”

“…Abnormal BALF cytology is associated with poor performance and exercise intolerance in both racehorses and nonracehorses 26, 29, 31, 34, 70, 71. Tracheal mucus accumulation was found to be positively correlated with BALF neutrophil percentage by some11 but not others26, 28, 64 and negatively correlated with BALF mast cell percentage 11…”

“…Racehorses presented for poor performance may exhibit lower red cell indices (hematocrit, hemoglobin, MCHC, MCV), but this finding is not specific for IAD 26, 33. Poorly performing horses with IAD tend to exhibit impaired physiological responses to exercise compared to healthy controls, as evidenced by lower speed for a blood lactate of 4 mmol/L and heart rate of 160 or 200 bpm 26, 29, 34. Horses with eosinophilic IAD might58 or might not49 exhibit peripheral blood eosinophilia independently of internal parasitism.…”