Electrolyte supplementation is utilized to support hydration in horses. However, limited data are available on formulations that include osmotically active compounds such as glycerol and creatine. These additional ingredients may enhance fluid retention, yet their physiologic effects in equine athletes have not been evaluated. This preliminary study assessed hematologic responses, body mass recovery, and voluntary water intake following moderate exercise with and without supplementation using a commercially available hydration supplement containing electrolytes, creatine, and glycerol. Six healthy quarter horses completed two conditions in a cross-over design: a water-only condition and a supplemented condition. Each study day consisted of a uniform moderate exercise regimen, a recovery period, and a 3-hour hydration period. Hematocrit and hemoglobin decreased over time in both conditions, while total protein concentrations were consistently lower in the supplemented condition. Calculated plasma volume (PV) increased to a greater extent with supplementation (p = 0.033). Body mass was preserved during the hydration period in the supplemented condition but declined in the water condition (p = 0.004). Horses also voluntarily consumed more water when supplemented (p = 0.0079). These preliminary findings suggest that an electrolyte supplement containing glycerol and creatine may augment post-exercise rehydration by promoting increased water intake, supporting PV expansion, and improving body mass recovery in moderately exercised horses.
Peterson et al. (Mon,) studied this question.