Estimation of urine flow rate in mares

Area of Science:

• Equine science
• Veterinary pharmacology
• Clinical pathology

Background:

• Accurate assessment of urine flow rate is crucial for determining drug excretion in horses.
• Traditional methods require precisely timed urine collection, which can be challenging in field or research settings.

Purpose of the Study:

• To establish a reliable method for estimating equine urine flow rate from untimed urine samples.
• To correlate urinary creatinine concentration with urine flow rate in Thoroughbred mares.
• To utilize estimated urine flow rates for predicting phenylbutazone excretion.

Main Methods:

• Quantitative collection of 228 urine samples from 12 healthy Thoroughbred mares across 53 experiments.
• Measurement of urine flow rate, creatinine concentration, osmolarity, and refractive index.
• Induction of diuresis using water or furosemide in specific sample collections.
• Administration of phenylbutazone prior to collection of 168 samples.

Main Results:

• A strong correlation was found between urinary creatinine concentration and urine flow rate (R² = 0.94).
• Urinary creatinine concentration effectively predicted urine flow rates ranging from 1.2 to 84.5 ml/min.
• Estimated urine flow rates were successfully used to predict phenylbutazone excretion.

Conclusions:

• Urinary creatinine concentration is a reliable predictor of urine flow rate in horses.
• This method allows for the estimation of urinary excretion without the need for quantitative urine collection.
• The findings simplify the assessment of drug pharmacokinetics and fluid balance in equine studies.