ELECTROLYTE BALANCE IN EXERCISING HORSES FED A CONTROL AND A FAT-SUPPLEMENTED DIET

Eight mature Thoroughbred horses were used in a replicated 4 x 4 Latin square experiment to verify the results of a previous study conducted in this laboratory which estimated dietary electrolyte requirements f or exercising Miniature Horses, and to evaluate the effect of feeding fat on electrolyte balance. The rations contained concentrations of el ectrolytes as suggested from the previous study. Horses were exercised at two work loads that increased digestible energy requirements to ap proximately 145% and 180% of maintenance, and were fed a control diet and a fat-supplemented diet. Each period of the Latin square was 3 wee ks. Mineral balance trials were conducted during the last 4 days of ea ch period. During the balance trials, horses were housed in metabolism crates, except while exercising, for total urine and fecal collection s. Sweat loss was quantified and sweat samples were collected. Feed, w ater, fecal, urine, and sweat samples were used to determine electroly te balances in exercising horses supplemented according to predicted n eeds. Sweat losses in horses in this study averaged 11.9 g/kg BW at th e lowest work load and 15.6 g/kg BW at the highest work load. There we re no significant differences in composition of sweat due to work load or diet. Furthermore, there was no effect on electrolyte balance due to diet. Horses were in near electrolyte balance when fed the concentr ations of sodium, potassium and chloride as predicted from a previous study conducted in this laboratory. Thus, to maintain exercising horse s in electrolyte balance, diets should contain (per Meal of DE) approx imately 1.3 g sodium, 3.1 g chloride and 4.5 g potassium.