4. Breuhaus BA. Thyroid function in mature horses ingesting endo- phyte-infected tall fescue seed. J Am Vet Med Assoc 2003;223(3): 340-345. EXERCISE PHYSIOLOGY - I 31601 Microhydrin Ò Supplementation Reduced Plasma Lactate in Exercising Standardbred Mares C.A. Williams,* 1 E.D. Lamprecht, 1 H. Roessner, 1 and K. Lloyd 2 , 1 Rutgers, the State University of New Jersey, New Brunswick, NJ, USA, 2 RBC Life Sciences Inc., Irving, TX, USA INTRODUCTION Microhydrin Ò is a unique dietary supplement composed of silica, potassium, magnesium and vitamin C. Colloidal sili- cate minerals display a variety of properties which include an increase in surface area, bonding absorbed water as well as mineral ions. 1 Structured water at the silica interface sta- bilizes electron transfer and creates a negative (-350 to -650mV) reduction/oxidation (redox) potentials. Specific silicate interactions play a substantial role in nutrient bioavailability by enhancing solubility properties, ion and water transport and provide free radical antioxidant protec- tion. Microhydrin Ò was shown to reduce post exercise lactic acid concentrations in a human cross-over trial as compared to placebo. 2 Lactic acid accumulation in the blood during heavy exercise in humans was shown to increase muscular ac- idosis and may inhibit optimal performance. 3 Post-exercise effects of lactic acid have been shown to create muscle sore- ness during, immediately and one to two days after exer- cise. 4 The purpose of this study was to evaluate the effect of Microhydrin Ò on lactic acid response in horses undergo- ing a sub-maximal treadmill exercise test. MATERIALS AND METHODS The study was run as a placebo controlled cross-over design using six unfit, yet healthy Standardbred mares aged 8.5  1.1 yr, weighing 537  17 kg, with a body condition score of 5.8  0.2. A month prior to the study horses performed a graded exercise test to exhaustion to determine their speed at maximum heart rate. At the start of the study three horses received 10 g of Microhydrin Ò (MH; RBC Life Sci- ences Inc., Irving, TX) daily top dressed onto their morn- ing feed, and three horses served as control (CON) with no additional supplementation. After 7 d of supplementation all six horses underwent a standard exercise test (SET) on an equine treadmill at a 6% grade. The SET consisted of 2 min walk, 1 min trot (4 m/s) proceeded by 65% of their speed at maximum heart rate (6.2-7.5 m/s) until fatigue (9-10 min). The day of the SET horses were fed their re- spective feed 60 min prior to the start of the SET. During each SET blood was collected immediately before exercise (PRE), at fatigue (FATIGUE), and 2, 5, 10, and 30 min post-exercise (REC). Heart rates and rectal tempera- tures were taken at each sample. Body weight was recorded before and after the SET. Samples were collected in sodium heparin blood gas syringes and Vacutainer tubes and serum separator tubes. Plasma and serum samples were aliquotted after being centrifuged for 5 min at 2500 x g. Plasma was analyzed for lactate and serum for creatine kinase (CK) and aspartate aminotransferase (AST), and whole blood was analyzed for blood gas (pO 2 and pCO 2 ), electrolytes (K, Na, Ca, Cl), pH and bicarbonate (HCO 3 ). After the first SET horses underwent a 7 d wash out before crossing over to receive the other treatment for another 7 d period when a second SET was performed. 2 Statistics were run as a re- peated measures ANOVA in SAS. RESULTS Horses maintained the same body weight and condition throughout the three week trial. Horses lost significantly less (P ¼ 0.021) weight after exercise when fed MH (1.5  0.3%) vs. when fed CON (1.8  0.4%). There were no differences between the first and second SET with any of the parameters measures indicating similar fitness through- out the study and a sufficient washout period. There were no differences between treatments in any of the blood gas and electrolyte parameters measured. There were no differ- ences between treatments for CK and AST. However, the exercise test was effective in increasing CK and AST after exercise effect (P < 0.0001), with the highest value found at FATIGUE. The overall effect of treatment for the lactate response for all sample times was significantly (P ¼ 0.032) lower for the MH group (4.98  0.13 mmol/L) as com- pared to CON (5.59  0.13 mmol/L). Particularly, the MH horses were 13.3% lower at FATIGUE (P ¼ 0.09; 8.02  1.04 mmol/L MH; 9.25  1.34 mmol/L CON) and 14.9% lower at 2 min REC (P ¼ 0.08; 7.22  1.15 mmol/L MH; 8.49  1.40 mmol/L CON) as compared to CON. DISCUSSION Study results showed a significant decrease in lactate re- sponse during and after exercise in mares fed the supple- ment. A similar study in human cyclists undergoing an endurance test showed a 23.7% lower whole blood lactate concentration in the cyclists supplemented with MH 5 min Abstracts  Vol 29, No 5 (2009) 301