Effect of a High-Protein Diet on Urinary Concentrations of Struvite Crystals and Insoluble Components in Cats

Abstract

Eight clinically normal adult cats were used to examine the effect of a high-protein diet on struvite crystals and insoluble components in urine. The cats were divided into two groups and allotted to two experimental dry foods in a switch-back design of 3 wk per period. One diet contained 29% crude protein (CP), whereas another contained 55% CP, on a DM basis. Ingestion of the high-protein diet decreased urinary pH but increased urine volume, although daily water intake did not differ between the groups. Urinary concentrations of Mg²⁺ and PO₄^3- decreased, in contrast to the urinary concentration of NH₄⁺ that was increased by ingestion of the high-protein diet. As a result, struvite activity product that was obtained by [Mg²⁺] x [NH₄⁺] x [PO₄^3-] was significantly decreased by ingestion of the high-protein diet. This implies the solubilization of struvite crystals and, in fact, urinary concentration and the daily amount of struvite crystals were significantly lowered in cats fed the high-protein diet. The high-protein intake also caused a decrease in the urinary concentration of total sediment including both HCl-soluble fraction (inorganic sediment) and HCl-insoluble fraction (organic sediment). However, the decrease was due to an increase in urinary volume, because daily amounts of these components were not affected by CP intake. Present results verified the effectiveness of a high-protein diet for the prevention of struvite urolithiasis in clinically normal cats.