PS7-6. Mineral Balance and Predicted Urinary pH Assessment in Extruded Grain-containing, Grain-free, and Urinary Tract Health Over-the-counter Cat Foods.

Abstract Dietary management is essential for feline urinary health and the prevention of struvite urolithiasis; specifically, high urinary pH (>6.4-6.6) and high magnesium (Mg) intake are recognized as key predisposing factors. The goal of this study was to evaluate the mineral balance and predicted urinary pH of commercial grain-containing (GC) and grain-free (GF) diets, comparing them with over-the-counter diets making specific urinary tract health (UTH) claims. Dry extruded, over-the-counter adult maintenance cat foods (n = 344) were screened (Chewy.com). Diets were categorized by ingredient composition and UTH claims: GC and GF (non-UTH), and UTH claim (regardless of whether GC or GF). Prescription, all life stages, and senior diets were excluded. Eighty diets were randomly selected and allocated into six groups: non-UTH GC and GF diets within two protein categories (27–33.5% and 33.5–40%; n = 17/group), and UTH-claim diets with or without low Mg and urinary pH control claims (27–40% protein; n = 6/group). Selected diets were submitted for proximate and mineral analyses, and predicted urinary pH was estimated according to Yamka et al. (2006) (pH_Y) and Jeremias et al. (2016) (pH_J). A pilot survey was conducted using the same methodology (n = 30; GC = 12; GF = 13; UTH= 5). Data from the pilot survey were analyzed with diet category as the main effect and crude protein on dry matter (DM) as a covariate. Minerals are reported on DM. Using pH_Y, GF had greater (P < 0.05) predicted urinary pH (7.61) compared to GC (7.19) and UTH (6.60), with the latter also being lower (P < 0.05) than GC. Similar results (P < 0.05) were observed using pH_J, though overall values were lower (GF = 7.00; GC = 6.36; UTH= 5.66); GC was comparable (P > 0.05) to the other two diets. Dietary Mg concentrations were greater (P < 0.05) in GF (0.15%), followed by GC (0.13%) and then UTH (0.09%). Dietary calcium (Ca) and phosphorus (P) were greater (P < 0.05) in GF (similar [P > 0.05] to GC) than in UTH diets; while Ca:P, sodium, chloride, and sulfur did not differ (P > 0.05) among groups. It is important to note that even small numerical changes in mineral concentrations can lead to major shifts in predicted urinary pH. Overall, this pilot survey suggests that the analyzed GF diets may lead to higher predicted urinary pH and dietary Mg intake, predisposing factors to struvite urolithiasis. However, the primary challenge lies not in the specific ingredient selection but in understanding their broader nutritional impact and ensuring precise mineral balance within the finished diet, which is attainable across any diet type by incorporating evidence-based strategies to support feline urinary health into the overall product formulation philosophy. Data from the larger survey is currently under analysis.