314 AJVR, Vol 71, No. 3, March 2010 O besity is of increasing concern in equid populations because its presence is associated with altered meta- bolic function and risk for disease. Obesity has been asso- ciated with insulin resistance in horses and ponies, 1–3 and Effects of exercise training on adiposity, insulin sensitivity, and plasma hormone and lipid concentrations in overweight or obese, insulin-resistant horses Rebecca A. Carter, PhD; L. Jill McCutcheon, DVM, PhD; Emanuela Valle, DMV, PhD; Elaine N. Meilahn, PhD; Raymond J. Geor, BVSc, PhD Objective—To determine effects of exercise training without dietary restriction on adiposity, basal hormone and lipid concentrations and glucose and insulin dynamics in overweight or obese, insulin-resistant horses. Animals—12 overweight or obese (body condition score ≥ 7), insulin-resistant (insulin sen- sitivity ≤ 1.2 X 10 –4 L/min/mU) geldings. Procedures—4 horses remained sedentary, and 8 horses were exercised for 4 weeks at low intensity and 4 weeks at higher intensity, followed by 2 weeks of detraining. Prior to and after each training period, frequently sampled IV glucose tolerance tests with minimal model analysis were performed and baseline plasma insulin, glucose, triglycerides, non- esterified fatty acids, and leptin concentrations were analyzed. Adiposity was assessed by use of morphometrics, ultrasonic subcutaneous fat thickness, and estimation of fat mass from total body water (deuterium dilution method). Results—Body weight and fat mass decreased by 4% (mean ± SD, 20 ± 8 kg) and 34% (32 ± 9 kg), respectively, compared with pre-exercise values, with similar losses during low- and higher-intensity training. There was no effect of exercise training on subcutaneous fat thick- ness, plasma hormone and lipid concentrations, or minimal model parameters of glucose and insulin dynamics. Conclusions and Clinical Relevance—Results suggested that moderate exercise training without concurrent dietary restriction does not mitigate insulin resistance in overweight or obese horses. A more pronounced reduction in adiposity or higher volume or intensity of exercise may be necessary for improvement in insulin sensitivity in such horses. (Am J Vet Res 2010;71:314–321) obesity and insulin resistance have been associated with impaired reproductive function in mares and an increased risk of and a predisposition for developing pasture-associ- ated laminitis. 4–7 In addition to insulin resistance, other obesity-associated factors have been implicated in increas- ing risk for pasture-associated laminitis, including hyper- insulinemia and hyperleptinemia. 8 Therefore, developing management strategies that mitigate the extent of obesity and insulin resistance is important for lessening disease risk in obese horses. Received February 16, 2009. Accepted April 8, 2009. From the Department of Animal and Poultry Sciences, College of Agricultural and Life Sciences (Carter, Valle, Geor), and the De- partment of Biomedical Sciences and Pathobiology (McCutcheon), Equine Medical Center (Meilahn), Virginia-Maryland Regional Col- lege of Veterinary Medicine, Virginia Tech and University of Mary- land, Blacksburg, VA 24061. Dr. Carter’s present address is Depart- ment of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348. Dr. McCutcheon’s present address is Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824. Dr. Geor’s present address is Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824. Supported by a grant from the United States Equestrian Federation and the John Lee Pratt Graduate Fellowship Program in Animal Nu- trition at Virginia Tech. Presented in part at the American College of Veterinary Internal Med- icine Forum, San Antonio, Tex, July 2008. Address correspondence to Dr. Carter (carterre@vet.upenn.edu). ABBREVIATIONS AIRg Acute insulin response to glucose BCS Body condition score DE Digestible energy FFM Fat-free mass FM Fat mass FSIGTT Frequently sampled IV glucose tolerance test NEFA Nonesterified fatty acid Sg Glucose effectiveness SI Insulin sensitivity TBW Total body water Unauthenticated | Downloaded 08/20/22 11:52 PM UTC