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  • Author or Editor: Hiromi Yamamoto x
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Objective—To evaluate effects of dietary carbohydrate on urine volume; struvite crystal formation; and calcium, phosphorus, and magnesium balance in clinically normal cats.

Animals—21 healthy adult cats (15 sexually intact males and 6 sexually intact females).

Procedure—Diets containing no carbohydrate source (control diet), control plus starch, or control plus fiber were given in a 3 × 3 Latin-square design. The diets were available ad libitum in study 1 (n = 12) and given under restrictions in study 2 (9) to equalize daily intakes of crude protein among the 3 groups. Formation of struvite crystals and balance of calcium, phosphorus, and magnesium were measured.

Results—Urine volume was lower in the starch group and fiber group in study 1, whereas no differences were detected among the groups in study 2. Urinary pH and struvite activity product were higher in the starch group in both studies, and the fiber group also had higher struvite activity product in study 2. In both studies, urinary concentrations of HCl-insoluble sediment were higher in the starch group and fiber group. In the fiber group, a net loss of body calcium, phosphorus, and magnesium was detected in study 2.

Conclusions and Clinical Relevance—Starch and fiber in diets potentially stimulate formation of struvite crystals. Hence, reducing dietary carbohydrate is desirable to prevent struvite urolith formation. In addition, a net loss of body calcium, phosphorus, and magnesium during feeding of the fiber diet suggests that dietary inclusion of insoluble fiber could increase macromineral requirements of cats. (Am J Vet Res 2004;65:138–142)

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in American Journal of Veterinary Research


Objective—To evaluate the effects of a high-protein diet versus dietary supplementation with ammonium chloride (NH4Cl) on struvite crystal formation in the urine of clinically normal cats by measuring the urine concentration of hydrochloric acid (HCl)-insoluble sediment, urine pH, struvite activity product (SAP), number of struvite crystals in urine, and urine volume.

Animals—23 healthy adult cats.

Procedure—Urine was fractionated by centrifugation with subsequent extraction of the sediment with 1 N HCl (study 1). Diets containing either 29% crude protein or 55% crude protein were fed to cats in a crossover trial of 3 weeks/period (study 2). Diets supplemented with either sodium chloride (NaCl) or NH4Cl were fed, by use of a 3 X 3 Latin-square design with 3 wk/period (study 3). In studies 2 and 3, urine samples were collected for the last 7 days of each period.

Results—The HCl-insoluble sediment contained Tamm-Horsfall glycoprotein (THP; study 1). The highprotein diet (study 2) and dietary supplementation with NH4Cl (study 3) resulted in a decrease in urine pH, SAP, and the number of struvite crystals in urine. However, the high-protein diet decreased urine concentrations of HCl-insoluble sediment containing THP (study 2), in contrast to the NH4Cl supplementation that increased urine volume without a significant effect on the urine concentration of the HCl-insoluble sediment (study 3).

Conclusions and Clinical Relevance—Our results indicate that compared with dietary supplementation with NH4Cl, the high-protein diet is preferable as a urine acidifier for the prevention of struvite crystal formation in clinically normal cats. (Am J Vet Res 2003;64:1059–1064)

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in American Journal of Veterinary Research