Dextrose Does Not Affect Rate of Absorption or Retention of Electrolytes in Idle Thoroughbreds

Two studies were conducted to evaluate the effects of dextrose or corn starch on uptake and retention of electrolytes and water in idle horses. In study 1, four Thoroughbreds (age: 6.25 ± 2.25 y; BW: 574.4 ± 82.4 kg) were used in a 4×4 Latin square trial. The horses were dosed with 92 g of electrolyte (72 g NaCl, 20 g KCl) either alone (elect), with 10 g of dextrose or 100 g dextrose. The electrolyte mixes were dissolved in 1 liter of water and administered via nasogastric tube. A fourth treatment of 1 liter water with no added electrolytes or dextrose served as a control. Plasma samples were taken before and for 4 hrs post dosing and Na⁺, K⁺, Cl-, BUN, and glucose were measured. The horses were offered water free choice and hourly water intake was measured for 4 hr dost dosing. Plasma Na⁺ and osmolality were significantly elevated post dosing in all three electrolyte treatments compared to the control (p<.05), but dextrose did not affect the rate or duration of increase. All electrolyte treatments increased voluntary water intake for the first 4 hr post dosing compared to the control (p<.05). Water intake equaled 0.3 ± .4 l, 5.3± 3.6 l, 5.4 ± 2.3 l, and 4.7 ± 2.5 l in the control, elect, 10 g dex and 100 g dex treatments, respectively.

A second 4X4 Latin square trial was conducted with four Thoroughbreds (age 6.25 yrs ± 2.25 yrs; weight 546.6 kg ± 35.2 kg). The horses were administered 1 mL distilled H₂O/100g BW + 0.15g/kg BW D₂O via nasogastric tube either (1) alone (control), (2) with 70 g NaCl + 30 g KCl (elect), (3) electrolyte + 10 g dextrose (dex), or (4)  electrolyte + 10 g starch (starch). Blood samples were taken immediately before and 0.5, 1, 2, 3 and 4 hrs post dosing and D₂O, Na⁺, K⁺, Cl^–, BUN, and glucose were measured. Plasma D₂O at 2 hr post dosing was used to calculate total body water. Total urine and fecal excretion was measured for 24 hr before dosing and at 12 hr intervals for 72 hr post dosing. Plasma Na⁺ and osmolality were significantly elevated post dosing in all three electrolyte treatments compared to the control (p<.05), but neither dextrose nor starch affected the rate or duration of increase. Plasma D₂O was elevated to a greater extent (p<.05) in the control compared to the three electrolyte treatments at 30 and 60 min post dosing, suggesting that isotonic electrolyte solutions delay water uptake compared to pure water. Total body water was unaffected by treatment and equaled 59.1 ± 6.3, 60.3 ± 5.3, 62.6 ± 7.7 and 58.4 ± 4.7 ml/kg BW for the control, elect, dex, and starch treatments, respectively. Urinary and fecal electrolyte excretion was not different between the three electrolyte treatments.

These studies suggest that adding dextrose or starch to electrolyte mixes does not increase rate of absorption or retention of electrolytes. Dextrose may still have some value in improving palatability of electrolyte mixes, but the higher the dextrose content, the lower the electrolyte content of a product. This means high-dextrose products supply lower amounts of electrolytes per kg, and may be less effective as a result.

Pagan, J.D., B.M. Waldridge, J. Lange. 2103. Dextrose does not affect rate of absorption or retention of electrolytes in idle Thoroughbreds. Journal of Equine Veterinary Science. 33(5):349-350. (Proceedings of the 2013 Equine Science Society Symposium)