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