Background: Chronic kidney disease (CKD) is a known risk factor for hypercalcemia in cats. Mechanistically, phosphorus restricted diets have also been implicated, potentially because phosphorus restriction increases the Ca:P ratio.Hypothesis/
Objectives: The primary objective of this study was to evaluate the impact of different therapeutic renal foods on ionized (iCa) and total (tCa) calcium in cats with early-stage CKD.Animals: Twenty colony-housed cats with stage 1 or 2 CKD were enrolled.
Methods: Two diets formulated for renal disease were utilized in a randomized, 140-day crossover study. One food provided 1.5 g/Mcal phosphorus and a Ca:P ratio of 1.2 (M-R); the other provided 1.1 g/Mcal phosphorus and Ca:P of 2.0 (H-R). Blood and urine samples were collected on days 0, 28, 86, and 140 before and after crossover. Data were analyzed using a linear mixed model with fixed effects of diet, period, day, and associated interactions.
Results: At baseline, all cats had iCa within the normal reference interval (1.10-1.30 mmol/L). At d28 and thereafter, cats fed H-R had higher iCa (1.48±0.04 mmol/L) compared with cats fed M-R (1.26±0.01 mmol/L; P< 0.001). Results were similar for tCa (normal reference interval: 8.80 to 10.00 mg/dL; A: 9.29±0.10 mg/dL; B: 11.36±0.36 mg/dL; P< 0.001). Conclusions and clinical importance: These data suggest that therapeutic renal diets may impact calcium status in cats with early-stage CKD, but the effect is formulation-dependent. Cats fed M-R maintained normal iCa and tCa, suggesting it is a safe and well-accepted option for cats with early-stage renal disease.
