Reference values of two-dimensional and M-mode echocardiographic measurements as a function of body size in various equine breeds and in ponies

Introduction: The aim of this study was to establish echocardiographic reference values for the equine species using allometric regression equations based on body weight (BW) and thoracic circumference (TC). Animals: A total of 239 horses or ponies were studied, including 65 warmbloods, 33 Standardbreds, 41 Thoroughbreds, 32 Arabian horses, 28 draft horses, and 40 ponies aged from 1 day to 30 years, weighing from 18 to 890 kg, with no evidence of cardiac disease. Methods: For each horse or pony, a two-dimensional and M-mode echocardiography was performed. Within each breed, the relationships between BW or TC and echo cardiographic dimensions were examined using power regression equations. Predictions and their 95% prediction intervals were calculated for the echocardiographic measurements. Results: Within each breed, all echocardiographic measurements showed a significant and positive relationship with a high coefficient of determination for the estimation of the regression equations using BW and TC as the main explanatory variables. Breed specific power regression equations as well as the 95% prediction intervals were calculated for each echocardiographic measurement as a function of BW and TC. Conclusions: In the future, the body size-corrected and breed-specific echocardio-graphic reference values calculated in the present study could be used to discriminate between normal and abnormal values in a given animal. (C) 2017 Elsevier B.V. All rights reserved.