OBJECTIVES: The aim of this study was to analyze iron, copper and zinc concentrations in commercial foods and compare among food formats (dry, canned, raw), foods marketed by age category (adult 1+ years and senior 7+ years) and foods intended for adult maintenance vs all life stages. METHODS: In total, 112 commercial non-therapeutic food products marketed for healthy adult and senior cats were purchased in the USA. Foods were analyzed for their proximate composition. Trace mineral concentrations were measured using inductively coupled argon plasma-optical emission spectroscopy and described on a calculated metabolizable energy basis using standard modified Atwater values. RESULTS: Measured iron (median 58.4 mg/1000 kcal [range 15.7-379.0]), copper (median 5.6 mg/1000 kcal [range 0.8-13.3]) and zinc (median 47.6 mg/1000 kcal [range 7.6-128.1]) concentrations were highly variable among cat foods. When all food products - regardless of their nutritional adequacy substantiation method - were compared with the Association of American Feed Control Officials regulatory minimums, 13/112 food products had a mineral deficiency, of which a majority (n = 11/13) were raw food products. Raw foods had significantly lower trace mineral concentrations compared with dry food products and, except for copper, canned food products. Cat foods marketed for senior cats had higher iron (P = 0.019) and zinc (P <0.0001) concentrations than foods marketed for adult cats. Foods intended for adult maintenance had higher iron (P = 0.003) and zinc concentrations than foods intended for all life stages (P <0.0001). CONCLUSIONS AND RELEVANCE: Iron, copper and zinc concentrations in commercial non-therapeutic foods for adult and senior cats are highly variable. A minority of foods - mainly raw food products - were deficient in these minerals. It is unknown if some foods with high trace mineral concentrations could have adverse effects as studies are needed to establish safe upper limits for dietary intake of trace minerals in healthy cats.

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

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.