Glycerol hyperhydration in resting horses.
Authors: Schott H C, Patterson K S, Eberhart S W
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Glycerol Hyperhydration in Resting Horses Schott and colleagues investigated whether glycerol administration could induce a state of transient hyperhydration in horses at rest, recognising that enhanced fluid retention might benefit performance or recovery in certain clinical contexts. Four horses received nasogastric treatments comprising glycerol in water, water alone, saline, or glycerol in saline, with plasma and urine parameters measured hourly for six hours total, whilst a second cohort's voluntary water intake was monitored following identical treatments. Glycerol-containing solutions increased serum glycerol concentration approximately 100-fold, raised plasma osmolality by roughly 10 mOsm/kg, and prompted the kidneys to conserve water despite increased solute excretion; notably, the glycerol-saline combination triggered horses to voluntarily drink an additional 5.2 litres during the first hour post-administration, compared with less than 1 litre across all five hours for other treatments. All four treatments produced modest plasma volume expansion (3.2–5.8%), but glycerol in saline achieved the most substantial and sustained hyperhydration through a dual mechanism: osmotic stimulation of drinking behaviour combined with enhanced renal water retention. For equine practitioners managing dehydration or considering pre-event fluid supplementation, these findings suggest that glycerol-saline formulations warrant consideration as they leverage the horse's natural thirst response whilst minimising the polyuria typically associated with water administration alone.
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Practical Takeaways
- •Glycerol administration in saline solution may provide a practical method to induce transient hyperhydration in horses before exercise or competition by enhancing both fluid retention and voluntary water drinking
- •The combination of glycerol in saline is more effective than glycerol in water alone for stimulating voluntary water intake in horses
- •This hyperhydration strategy could have applications for improving thermoregulation or endurance performance in resting horses prior to work
Key Findings
- •All four treatments produced mild plasma volume expansion ranging from 3.2 to 5.8% in resting horses
- •Glycerol-containing solutions increased serum glycerol concentration approximately 100-fold and plasma osmolality by ~10 mOsm/kg
- •Glycerol in saline (GS) stimulated voluntary water intake of 5.2 ± 0.9 L in the first hour post-administration, compared to <1.0 L for other treatments over 5 hours
- •Glycerol-containing solutions enhanced renal water conservation despite increased osmole excretion, suggesting transient hyperhydration potential