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Comparison of volumetric urine collection versus single-sample urine collection in horses consuming diets varying in cation-anion balance

Erica C. McKenzie BSc, BVMS1, Stephanie J. Valberg DVM, PhD2, Sandra M. Godden DVM, DVSc3, Joe D. Pagan PhD4, Gary P. Carlson DVM, PhD5, Jennifer M. MacLeay DVM, PhD6,7, and Flavio D. DeLaCorte DVM, PhD8,9
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  • 1 Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 2 Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 3 Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 4 Kentucky Equine Research Inc, 3910 Delaney Ferry Rd, Versailles, KY 40383.
  • | 5 Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 6 Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 7 Present address is Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.
  • | 8 Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.
  • | 9 Present address is Universidade Federal de Santa Maria, Departamento de Clinica de Grandes Animais, Centre de Ciencias Rurais, 97105-900 Campus Camobi, Santa Maria, Rio Grande do Sul, Brazil.

Abstract

Objective—To determine daily variation in urinary clearance and fractional excretion (FE) of electrolytes and minerals within and between horses and to compare volumetric and single-sample urine collection for determining FE values of diets with a range of dietary cation-anion balance (DCAB).

Animals—5 Thoroughbred and 6 mixed-breed mares.

Procedure—3 isocaloric diets with low, medium, and high DCAB values (85, 190, and 380 mEq/kg of dry matter, respectively) were each fed for 14 days. Daily blood samples, single urine samples collected by using a urinary catheter (5 mares), and volumetric urine collections (6 mares) were obtained during the last 72 hours of each diet.

Results—Urine and plasma pH values, plasma concentrations, and FE values of sodium, chloride, potassium, magnesium, phosphorus, and calcium were altered by varying the DCAB. Noticeable variation in clearance and FE values was detected within horses from day-to-day on the same diet as well as between horses. Fractional excretion values were not significantly different between single-sample and volumetric methods, except for magnesium in the high DCAB diet. Volumetric and single-sample collections revealed similar patterns of change in urinary FE values with varying DCAB, except for calcium and magnesium.

Conclusions and Clinical Relevance—Substantial variation in clearance and FE of electrolytes and minerals are evident within horses between 24-hour periods as well as between horses fed a specific diet. Three daily urine samples provide similar information regarding dietary-induced changes in clearance and FE values (excluding calcium and magnesium) as that obtained by volumetric urine collection. (Am J Vet Res 2003;64:284–291)

Abstract

Objective—To determine daily variation in urinary clearance and fractional excretion (FE) of electrolytes and minerals within and between horses and to compare volumetric and single-sample urine collection for determining FE values of diets with a range of dietary cation-anion balance (DCAB).

Animals—5 Thoroughbred and 6 mixed-breed mares.

Procedure—3 isocaloric diets with low, medium, and high DCAB values (85, 190, and 380 mEq/kg of dry matter, respectively) were each fed for 14 days. Daily blood samples, single urine samples collected by using a urinary catheter (5 mares), and volumetric urine collections (6 mares) were obtained during the last 72 hours of each diet.

Results—Urine and plasma pH values, plasma concentrations, and FE values of sodium, chloride, potassium, magnesium, phosphorus, and calcium were altered by varying the DCAB. Noticeable variation in clearance and FE values was detected within horses from day-to-day on the same diet as well as between horses. Fractional excretion values were not significantly different between single-sample and volumetric methods, except for magnesium in the high DCAB diet. Volumetric and single-sample collections revealed similar patterns of change in urinary FE values with varying DCAB, except for calcium and magnesium.

Conclusions and Clinical Relevance—Substantial variation in clearance and FE of electrolytes and minerals are evident within horses between 24-hour periods as well as between horses fed a specific diet. Three daily urine samples provide similar information regarding dietary-induced changes in clearance and FE values (excluding calcium and magnesium) as that obtained by volumetric urine collection. (Am J Vet Res 2003;64:284–291)