Background High dietary phosphorus (P) and low calcium‐to‐phosphorus ratio (Ca:P) are associated with kidney damage in cats. There are no established guidelines for dietary P maximum for cats. Objectives To quantify crude protein, P, Ca, and magnesium (Mg) concentrations in cat foods and compare among food formats (dry, canned, raw), primary protein ingredients, protein concentrations (low, moderate, high), grain‐free versus grain‐containing foods, foods intended for adult maintenance versus all life stages, and cost. Samples Eighty‐two commercial nonprescription cat foods. Methods Descriptive study. Mineral concentrations were measured using inductively coupled argon plasma‐optical emission spectroscopy. Crude protein was measured using the Dumas nitrogen combustion method. Mineral and crude protein concentrations were compared among food categories. Results Twenty‐seven foods contained ≥3.6 g P/1000 kcal metabolizable energy (ME), of which 7 exceeded 4.8 g/1000 kcal ME. Thirteen foods had low Ca:P ratio (≤1.0). The low‐protein diet group had no products ≥3.6 g P/1000 kcal ME, which was significantly different compared to the high‐protein diet group (52% of products had ≥3.6 g P/1000 kcal ME; P = .01). No significant differences in P content and Ca:P ratio were found among other diet categories. Canned foods had significantly lower Mg compared to dry (P < .001) and raw (P = .007) foods. Declared minimum P and Ca were significantly lower than analyzed concentrations (P = .0005 and P = .003, respectively). Conclusions and Clinical Importance The high number of foods with high P and low Ca suggest that pet food regulatory reform should be considered.

Background Straight‐ and branched‐chain (BCFA) short‐chain fatty acids (SCFAs) are produced by colonic microbiota and have both beneficial and deleterious effects in humans with chronic kidney disease (CKD). Fecal SCFAs in cats with CKD have not been described. Objective To characterize fecal SCFA concentrations in cats with CKD as compared to healthy geriatric cats and correlate SCFA to serum indoxyl sulfate (IS) and p‐cresol sulfate (pCS) concentrations. Animals Twenty‐eight cats with CKD (International Renal Interest Society [IRIS] stages 2, 3, and 4) and 11 older (≥ 8 years) healthy geriatric cats. Methods Prospective, cross‐sectional study. Voided feces were analyzed using stable isotope dilution gas chromatography‐mass spectrometry to determine fecal concentrations of SCFAs. Serum concentrations of IS and pCS were measured using liquid chromatography tandem mass spectrometry. Results Fecal isovaleric acid concentrations were significantly higher in CKD cats(P = .02) Cats with IRIS CKD stage 3 and 4 had significantly higher fecal isovaleric acid concentrations compared to healthy geriatric cats (P = .03), but not compared to IRIS CKD stage 2 cats. Total fecal concentrations of BCFAs were found to correlate weakly with serum creatinine concentration (rho, 0.33; P = .05), blood urea nitrogen concentration (rho, 0.40; P = .01), and pCS concentration (rho, 0.35; P = .04). Conclusions and Clinical Importance Fecal isovaleric acid concentrations were higher in CKD cats, particularly in late stage disease, compared to healthy geriatric cats. Fecal BCFA concentrations correlated with pCS and were higher in cats with muscle wasting, providing evidence for malassimilation of protein in CKD cats.

Age-related changes in gastrointestinal function have been reported in companion animals, but the impact on digestive efficiency remains uncertain. Healthy dogs (n = 37; 2.6–14.2 years) received four diets varying in total dietary fibre (TDF; 6–29%, as fed). Healthy cats (n = 28; 1–13 years) received four diets with two fat (10–12%; 17–18%) and TDF (9 and 12%) levels. In a crossover design, diets were provided over four consecutive 10-day cycles, including a 4-day faecal collection. Apparent crude protein (CP), ether extract (EE), TDF, calcium (Ca), and phosphorus (P) digestibilities were determined. The effect of age was analysed as a continuous variable in dogs and as differences between adult (1–5 years) and senior (7–13 years) cats. In dogs, EE digestibility was unaffected by age (p > 0.10). Dogs of 6–12 years had higher digestibility of CP (p = 0.032), TDF (p = 0.019), Ca (p = 0.019), and P (p = 0.024) when fed the 6% TDF diet. Senior cats had greater digestibility of TDF (p < 0.01) and Ca (p = 0.024) but had lower EE and CP digestibility with one diet (17% fat; 9%TDF) (age, p > 0.10; diet × age, p < 0.001). Healthy ageing was associated with preserved nutrient digestibility in dogs and cats within the age ranges studied. The effect of ingredient sources in senior cats warrants further investigation.

Background Cat foods marketed for senior cats (≥7 years) are available to owners. The variability in the nutritional content of these foods is unknown. Objectives To measure the caloric density and caloric distribution of crude protein, crude fiber, crude fat, phosphorus, calcium, magnesium, sodium, potassium, and vitamin D3 in commercially available foods for senior cats and to compare nutrient content with foods for adult cats. Samples Thirty‐one senior and 59 adult commercial nontherapeutic cat food products. Methods Descriptive study. Crude protein, crude fiber, and crude fat were measured using Dumas nitrogen combustion, Ankom filter bag technique, and acid hydrolysis, respectively. Mineral concentrations were measured using inductively coupled argon plasma‐optical emission spectroscopy. Vitamin D3 was determined by liquid chromatography with tandem mass spectrometry. Caloric density was calculated using modified Atwater values. Results The evaluated nutrient concentrations in all foods for senior cats met the values of the Association of American Feed Control Officials Cat Food Nutrient Profile for adult maintenance. Foods for senior cats had significantly higher crude fiber content when compared to foods for adult cats (P < .0001). No significant difference in crude protein, crude fat and mineral concentrations was found between foods for senior and adult cats. Conclusions and Clinical Importance Foods marketed for senior cats are highly variable in their caloric density and nutrient content and, except for crude fiber, are similar to foods for adult cats. Veterinarians should avoid broad recommendations regarding commercially available foods for senior cats, and dietary recommendations should reflect the patient's individual needs.