Domestic cats and dogs require their diet to provide essential minerals that their bodies are unable to produce. In the UK, 41% of dogs and 77% of cats are feed wet pet foods (tins, pouches etc) complemented with other foods like table scraps, treats etc. Based on these percentages, it is imperative that commercial pet foods provide sufficient but not excessive amount of essential minerals.

In Europe, the Federation Europeene De l’industrie des aliments pour Animaux Familiers (FEDIAF) establishes animal feeding nutrition guidelines. In the US, AAFCO (American Association of Feed Control Officials) maintains a similar framework. Both organisations base their nutrition guidelines on the National Research Council’s recommendations for companion animal nutrient requirements. However, for some minerals the European nutrition guidelines do not specify the recommended quantity that may or should be included in pet foods. Nor does it define for others the maximum amount that may be fed without adverse consequences.

Review of pet food available in Europe

A recent study assessed the mineral composition of a wide range of wet and dry pet foods available in Europe. They were assessed again 11 of 13 European nutrition guidelines, as defined by the FEDIAF.

177 pet foods were included in the assessment. All foods were labelled as “complete” which means the food is intended as the only source of nutrition for the cat or dog. The breakdown of the products included in the review was as follows:

• 139 for adult pets

• 14 for young animals

• 24 for seniors

• 42 different brands were represented

• 113 products for cats – 48 wet, 65 dry

• 64 products for dogs – 49 wet, 15 dry

The FEDIAF guidelines specify quantities of macronutrients i.e. crude protein, fat, ash etc) that should be included in pet food. The guidelines also provide recommendations for the following: calcium, phosphate, Calcium: Phosphorus ratio, potassium, sodium, chloride, magnesium, copper, iodine, iron, manganese, selenium and zinc.

The allowable amounts of heavy elements such as arsenic, cadmium, mercury and lead in pet foods is specified by a European Union directive. (2002/32/EC)

Findings

Analysis of the foods indicated broad non-compliance with the European feeding guidelines – 94% of wet foods and 61% of dry foods failed to comply with all guidelines. A majority of the products included in the review compiled with 8 or more of the guidelines. However, many products (20% of dry food and 29% of wet food) had marked mineral imbalances particularly in relation to calcium to phosphorous ratio.

In terms of non-compliance, the study highlighted selenium, copper and arsenic quantities in the pet food.

Selenium

76% of the pet foods assessed had greater than the maximum concentration of selenium. Seven products had more than three times the maximum amount.

While, selenium toxicity is relatively rare, it has been observed in laboratory animals (rabbits, rats, dogs, cats). In laboratory conditions, the minimum lethal dose of selenite or selenate was 1.5 – 5.0 mg / Kg body weight. Signs of acute poisoning are “garlic” smelling breath, vomiting, spasms and death from respiratory failure.

Sufficient concentrations of selenium are required to prevent oxidative damage and support hormone balance in the animal’s cells. The best food sources of selenium are fish, meat and eggs followed by cereals.

Copper

Copper was another mineral where the concentrations varied widely from the recommended quantities. Some diets had more than twice the maximum amount while other had less than half the minimum amounts.

The function of copper in the animal’s body is closely linked to that of iron. Copper is required so the animal is able to absorb and transport iron. Copper is also required for the formation of haemoglobin.

Further, as a component of a metalloenzymes, copper is required for the following processes:

• Production of pigment melanin (Coat colour)

• Synthesis of collagen and elastin (connective tissues)

• Production of ATP (energy at a cellular level)

• Contributes to osteoblast activity during skeletal development

Signs of copper deficiency include a form of anaemia similar to iron deficiency, depigmentation of coloured coat, impaired skeletal growth in young animals. It can also affect the absorption and transport of iron.

Good food sources of copper are organ meats particularly liver.

Arsenic

Two foods in the study contained arsenic concentrations about the legal maximum for animal feed. Soil and marine sources can become contaminated with arsenic which accumulates in the animals and fish that inhabit these environments. When these animals or fish are consumed, arsenic accumulates in the liver and kidney of pet cats and dogs. Concentrations of arsenic can become toxic in its own right and via interactions with other minerals.

Limitations of the study

The study did not assess the bioavailability of minerals to pet cats and dogs. Based on this, any conclusions about the likelihood of the pet food products contributing to mineral deficiency or toxicity cannot be drawn as the study simply assessed the concentration of nutrients not how they were digested and absorbed.

Takeaway messages for pet owners:

• Some pet food may not actually comply with the feed standards (AAFCO or FEDIAF) to which they claim compliance.

• The feed standards do not specify maximum limits for some nutrients so the pet food product may contain very high concentrations of some nutrients. High concentrations of one nutrient may cause imbalances with others e.g. calcium and phosphorous.

• The environments in which pet food ingredients are sourced may be toxic. Hazardous substances can accumulate in the animals and fish that are fed to our pets.

• Feeding human grade, whole foods such as fish, meat and organs where you know the source of the ingredients ensures you are feeding your pets good quality sources of minerals and reduces the risk of feeding contaminated ingredients.

Full Stride provides canine remedial massage and nutrition advice to keep dogs active and healthy into their senior years.

Until next time, enjoy your dogs.

Sources:

Davies, M., Jones, L., Alborough, R., Davis, C., Williams, C., & Gardner, D. S. (2017). Mineral analysis of complete dog and cat foods in the UK and compliance with European guidelines. bioRxiv, 172544.

Koca, A. F., Koca, I., & Tekguler, B. (2015, May). Two antoxidant elements of Allium vegetables: Germanium and Selenium. In VII International Symposium on Edible Alliaceae 1143 (pp. 297-302).

Koller, L. D., & Exon, J. H. (1986). The two faces of selenium-deficiency and toxicity—are similar in animals and man. Canadian Journal of Veterinary Research, 50(3), 297.