It is a key component of hemoglobin (the protein in red blood cells that transports oxygen from the lungs to all tissues) and myoglobin (which stores oxygen in the muscles). It is also responsible for the proper functioning of the immune system and many enzymes [1] [2]. It occurs in cytochromes, responsible for electron transport. Iron homeostasis in the body is maintained mainly by regulating its absorption in the gastrointestinal tract. There are 2 forms of iron present in food; heme (in hemoglobin and myoglobin) and non-heme (in cereals and other plant products). The absorption of heme and non-heme iron is inhibited by calcium [3], so they should not be administered together. The absorption of non-heme iron is determined by a number of factors; the presence of phytates, tannins, excess phosphorus, manganese, copper or ascorbic acid in the diet. Therefore, there are three factors that determine the absorption of iron: its level in the body, availability in the diet and the amount of heme and non-heme forms in a given [3] product.
What it contains: Whole blood and dried hemoglobin (pork or beef), spleen, liver, kidneys, heart, sardines, and dark meats (beef, horse meat, duck), egg yolk (less available), spinach, pumpkin seeds, sesame seeds.
Deficiency: Anemia, rapid fatigue and general weakness of the body, distorted appetite (e.g. licking walls, eating dirt) [4].
Excess: Resulting from a natural diet alone is unlikely because the body of a healthy animal then limits its absorption in the intestines. However, overdose of synthetic [2] supplements is risky. It may cause poisoning, the symptoms of which are:
Very small amounts of iron are excreted in urine, and a small amount in sweat or hair. Stool may contain iron that has not been absorbed.
Sources
- 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
- 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
- Wedekind, K. J., Yu, S., Kats, L., Paetau-Robinson, I., & Cowell, C. S. (2010). Micronutrients: Minerals and vitamins. In M. S. Hand, C. D. Thatcher, R. L. Remillard, P. Roudebush, & B. J. Novotny (Eds.), Small Animal Clinical Nutrition (5th ed., Chapter 6). Mark Morris Institute. https://www.markmorrisinstitute.org/sacn5_download.html
- 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/