Relação entre obesidade e ocorrência de síndrome metabólica equina em cavalos crioulos

Abstract

The Crioulo horses that were kept on native grassland, are now being bred confined to box stalls, fed high carbohydrate diets or on high energy pastures. These changes resulted in obesity and developmental musculoskeletal problems. Today, it is known that overweight animals are more prone to develop equine metabolic syndrome (EMS). This clinical syndrome, in addition to being associated with increased adiposity, is also characterized by insulin resistance (IR) and laminitis. In view of this and considering the limited literature regarding this breed, the aim of this study was to investigate EMS in obese Crioulo horses, evaluating the applicability of an oral sugar test (OST) to its diagnosis. Twenty-two Crioulo horses from different properties of Rio Grande do Sul were allocated into three groups according to their body condition score (BCS) and presence or absence of laminitis as follows: CON or G1 (6/22), BCS<7; OB or G2 (8/22), BCS ≥7 and LAM or G3 (8/22), BCS ≥7 with clinical and/or radiographic signs of laminitis. A complete clinical history and exam was obtained, followed by radiographic evaluation of front feet and by ultrasonography measurements of subcutaneous body fat on the rear of the rump, withers, behind the scapula and at retroperitoneal region. Morphometric measurements, BCS and cresty neck score (CNS) were also determined. For the OST, animals were fasted for eight hours overnight and blood samples were collect for glucose concentration before and 30, 60, 75, 90, 120, 150, 180, 210 and 240 min after sugar administration. Insulin was determined on the basal sample, at 75 min and at the peak glucose. Horses from G3 presented the highest morpho-metric measurements and insulin plasma concentration among the groups. Morphometric and metabol-ic differences (P < 0.05) were observed between G1 animals and obese ones. In nine obese horses (56,25%), the glucose peak, as the insulin peak response to OST, occurred in a different time (120-180 min) from the one described in literature (60-90 min). Furthermore, delaying time to return to glucose baseline levels was observed in most obese horses characterizing IR in 69% (n=11/16). The detection of IR through the oral sugar test was only possible because the glycemic curve was performed, once the plasma insulin concentrations were within reference ranges. The subcutaneous fat ultrasound measurement at the tail-head showed the highest correlation (R=0,87) with IR. Sampling at 75 minutes, as preconized for hyperinsulinism detection, without monitoring of the plasma glucose curve, was considered inadequate for the obese animals. These results indicate that there are clear obesity related differences in the glucose and insulin responses of Crioulo horses to oral sugar test, reinforcing the association between this condition and metabolic disturbs. Results of this study increase the accu-racy in the early diagnosis of this condition, allowing it to be identified before serious consequences such as laminitis occur.