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Iron - Fe in dog and cat diets

A short guide to the role of Iron - Fe in dog and cat nutrition.

Iron - Fe

It is a key component of haemoglobin (the red blood cell protein that carries oxygen from the lungs to the tissues) and of myoglobin (which stores oxygen in the muscles). It also participates in energy production in the mitochondria and in the work of the immune system [1] [2]. Iron from animal tissues (heme) is absorbed with an efficiency of 15–35%, while plant and synthetic (non-heme) iron only 2–10% — and is strongly inhibited by calcium and phytates [3]. This is a big advantage of BARF: iron from meat and offal is absorbed much better than from supplements or plant foods. Iron is one of the more frequently deficient minerals in home diets [4].

Where it's found: Spleen (the best source — 5–10 times more iron than muscle meat, without the risk of excess vitamin A), whole and dried blood, kidneys, heart and dark red meats (beef, horse, lamb, game). Liver is rich in iron, but raising iron with it risks hypervitaminosis A — keep it within 5–10% of the diet [5]. Poultry and fish are relatively poor in iron.

Deficiency: Microcytic anaemia (pale gums, quick tiring, accelerated breathing, lack of appetite, sometimes pica — licking walls, eating gravel) [6]. The most common dietary cause is a diet based mainly on poultry, without red meat and offal from red-meat animals. Important: pale gums are a signal to see a vet, not to add iron — anaemia more often results from disease (parasites, inflammation, kidney disease) than from diet [2].

Excess: Unlikely from a natural diet alone — a healthy body regulates non-heme iron absorption with hepcidin. The risk grows when sources are stacked (spleen + dried blood + premix with iron) and with synthetic supplements, which act pro-oxidatively and damage the liver, heart and pancreas [2]. Swallowing human iron tablets is a life-threatening state — go to the vet immediately.

Species difference

Iron deficiency is more common in cats than in dogs. Many cats prefer chicken and the owner builds the whole diet around it, while poultry is poor in iron; on top of that, cats have a higher requirement per kg of body weight [1]. Plant sources (spirulina, algae, parsley) are practically worthless for the cat — only heme iron from animal sources counts. A separate problem is chronic kidney disease in older cats: diseased kidneys produce less erythropoietin, so the anaemia won't resolve from increasing iron alone — a comprehensive veterinary approach is needed [2] [7].

What to watch for

Copper is essential for proper blood formation (ceruloplasmin oxidises iron into the form transported by transferrin) — its deficiency gives anaemia despite sufficient iron, which is why anaemia doesn't always mean a problem with iron itself [2]. More in the article Copper. Chronic zinc excess indirectly worsens copper metabolism, and through it iron metabolism [1]. The best strategy is rotating meat species in a weekly cycle, rather than daily adding one "iron bomb". If the calculator shows low iron — reach for spleen, not a supplement; rebuilding stores after depletion takes months, so prevention is more effective than correction.

Sources

  1. National Research Council (2006). Nutrient Requirements of Dogs and Cats, Chapter 7 — Minerals. National Academies Press. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
  2. McCown JL, Specht AJ (2011). Iron Homeostasis and Disorders in Dogs and Cats: A Review. Journal of the American Animal Hospital Association. https://doi.org/10.5326/JAAHA-MS-5553
  3. Hand MS, Thatcher CD, Remillard RL, Roudebush P, Novotny BJ (2010). Small Animal Clinical Nutrition, 5th Edition. https://www.markmorrisinstitute.org/sacn5.html
  4. Pedrinelli V, Zafalon RVA, et al. (2019). Concentrations of macronutrients, minerals and heavy metals in home-prepared diets for adult dogs and cats. Scientific Reports 9:13058. https://doi.org/10.1038/s41598-019-49087-z
  5. United States Department of Agriculture (2024). USDA FoodData Central. https://fdc.nal.usda.gov/
  6. Naigamwalla DZ, Webb JA, Giger U (2012). Iron deficiency anemia (review). Canadian Veterinary Journal 53(3):250-256. https://pmc.ncbi.nlm.nih.gov/articles/PMC3280776/
  7. Hunt AC, et al. (2021). Anemia, iron deficiency, and cobalamin deficiency in cats with chronic gastrointestinal disease. Journal of Veterinary Internal Medicine. https://doi.org/10.1111/jvim.15962