Evaluation of oral sugar test response for detection of equine metabolic syndrome in obese Crioulo horses

Abstract

Owing to the high prevalence of obesity in Crioulo horses, information allowing early diagnosis of equine metabolic syndrome (EMS) and prevention of the associated laminitis is of great value. The aim of this study was to evaluate the occurrence of EMS and the response to an oral sugar test (OST) in obese Crioulo horses. Twenty-two Crioulo horses were allocated into 3 groups according to their body condition score (BCS out of 9) and presence or absence of laminitis as follows: CON (6/22), BCS < 7; OB (8/22), BCS ≥ 7; and LAM (8/22), BCS ≥7 with clinical and/or radiographic signs of laminitis. A complete clinical history was obtained, followed by a physical examination, morphometric measurements, radiographic evaluation of front feet, and ultrasonography measurements of subcutaneous body fat. For the OST, animals were fasted overnight, and blood samples were collected for glucose and insulin concentration before and after sugar administration. Morphometric and metabolic differences (P < 0.05) were observed between CON animals and obese ones, with horses from the LAM group presenting the highest morphometric measurements and insulin plasma concentrations. A delayed peak glucose response for OST was observed in the majority of obese animals, indicating that sampling between 60 and 90 min after sugar administration without glycemic curve follow-up, as previously used for hyperinsulinism detection, can be inadequate. The observed delay in the return to glucose baseline levels, combined with high insulin levels, supports the diagnosis of insulin dysregulation. These results indicate that there are clear obesity-related differences in the glucose and insulin responses of Crioulo horses to an OST.