2016 ACVIM Forum Research Abstract Program

SELENIUM DEFICIENCY ASSOCIATED WITH THE DEATHS OF FIFTEEN ADULT HORSES. Andrew Allen, Debra Sellon, Fairfield Bain, Danielle Nelson. Washington State University, Pullman, WA, USA Nutritional myopathy due to selenium (Se) deficiency typically presents itself in young rapidly growing calves, lambs, kids, and foals. Reports of myodegeneration secondary to selenium deficiency in adult horses are less frequent. We investigated 2 herds with nutritional myopathy with generalized skeletal muscle degeneration and significant death loss in adult horses. In 2014, two American Paint horses from the same farm presented to our diagnostic laboratory for post mortem evaluation. Significant necropsy and histopathology findings included myonecrosis of the cardiac and skeletal muscles, widespread subcutaneous edema, pleural effusion and ulcerative glossitis. An on farm investigation was performed where it was discovered that 13 horses, including the two presented horses, had died on this farm with similar clinical signs over the last year. Complete blood counts and serum chemistry panels were performed on 4 of the 12 remaining horses and physical examinations were performed on the entire herd. All four horses had elevated creatinine kinase activity (CK) and aspartate aminotransferase (AST) levels, the herd had an overall low body condition score, 3 horses had elevated heart rates, and one horse had pitting ventral edema. All of the horses had extremely low blood selenium levels, no box elder trees were found on the farm and gastric contents of the dead horses and feed supplements were found to be free of ionophores. An on farm echocardiographic study was performed 6 months post initial investigation on three of the most severely affected horses. All findings appeared within normal limits. In 2015 a second investigation of two dead horses revealed a very similar scenario and herd wide myodegeneration secondary to selenium deficiency. Although unusual, selenium deficiency should be considered a rule out with adult horses showing signs of ventral edema, weakness, and abrupt death. Processed concentrate feeds contain a high concentration of sugars and in some cases non-structural carbohydrates (NSC) exceed 35%. These feeds are commonly fed to stall-confined horses, especially those in competition. Grains, high in NSC, can overwhelm glucose receptors in the proximal small intestine and increase delivery of sugars to the hindgut leading to fermentation and colonic acidosis. Feed supplements, that might enhance glucose absorption in the small intestine, would provide more energy substrate for exercise and decrease delivery of sugars to the hindgut. The purpose of this study was to determine effects of a feed supplement (ALF; Alfa-Lox Forage, Triple Crown Nutrition, Inc., Wayzata, MN), containing chopped alfalfa hay, mannanoligosaccharides, Omega 3 Fatty Acids, and L-Carnitine, top-dressed on grain, on plasma glucose concentration and serum insulin activity in horses before and after grain feeding. Eight healthy Thoroughbreds (7 geldings and 1 mare; ages 2-12 yrs.) were used in a 2-period cross over study, where horses were fed ALF (2.0 lbs. [0.91 Kg], twice daily) top dressed on a sweet feed grain (2.5 Kg; Omelene Ã’ 100, Purina Animal Nutrition, LLC., Grey Summit, MO) or control (grain alone) for 56 days, as part of another study. On Days 41 and 48, after withdrawing feed overnight, blood samples were drawn at 8 am, before the morning grain feeding, with or with