Implications of highly absorbed soluble phosphorus for renal health and urine supersaturation for struvite and calcium oxalate in cats

• Grant number: 23/06608-2
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: November 01, 2023
• End date: May 31, 2026
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Clinics and Surgery
• Principal Investigator: Aulus Cavalieri Carciofi
• Grantee: Maria Eduarda Gonçalves Tozato
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
• Associated scholarship(s): 24/19736-1 - Implications of high absorption soluble phosphorus for renal health and urinary oversaturation of struvite and calcium oxalate in cats: discussion and interpretation of results, BE.EP.DR

Abstract

Highly available inorganic sources of phosphorus (P) might induced increased postprandial serum P concentration, stimulating the secretion of fibroblast growth factor 23 (FGF-23) and parathyroid hormone (PTH), resulting in increased renal P excretion. Concerns exist about the implications of these mechanisms for kidney health. Phosphoric acid is a common source of soluble P included in cat foods as a urine acidifier agent. As little information is published regarding the safety of inorganic sources of P, the aim of the present study is to compare phosphoric acid with ammonium chloride as urine acidifying agents for cats, and their effects on renal phosphorus excretion, phosphorus metabolism, parameters of kidney health, water balance and urinary supersaturation (RSS) for calcium oxalate and struvite. Additionally, the addition of P from an inorganic source (phosphoric acid) will be compared with an organic source (bone) regarding its apparent absorption, renal excretion, phosphorus metabolism, kidney health parameters and RSS for struvite calcium oxalate. Four diets will be used, a control formulation that will be unfolded into three treatments: 0.75% phosphoric acid (addition of -115 mEq to induce urine acidifications.); 0.65% ammonium chlorite (addition of -114 mEq, same urine acidifications but with another anion); 3% high ash meat and bone meal (similar P addition but from an organic less available source). Four diets will be used, a control formulation that will be unfolded into three treatments: 0.75% phosphoric acid (addition of -115 mEq to induce urine acidification); 0.65% ammonium chloride (addition of -114 mEq, same acidifications as in urine, but with another anion); 5% high ash meat and bone meal (similar P addition but from an organic less available source). Diets will be tested in eight cats, following a two 4x4 Latin square design. Cats will receive food for 31 days and the following parameters will be assessed: Ca and P apparent absorption and renal excretion; urine characteristics (pH, specific gravity, volume); Hydric balance; hemogasometry; P metabolism with Ca, P, FGF-23, CrossLaps and PTH dosages; urine RSS for struvite and calcium oxalate; renal health parameters (kidney architecture by ultrasound, symmetric dimethylarginine (SDMA), creatinine clearance, microalbuminuria, urine albumin:creatinine ratio). Data will be evaluated by analysis of variance and means compared by Tukey test (P<0.05).