It belongs to the group of fat-soluble vitamins. Its main task is to manage the calcium and phosphorus metabolism, without it calcium will not be absorbed from the intestines into the blood, and bones and teeth will not be able to mineralize properly [1]. Neither dogs nor cats can produce it effectively in their skin when exposed to sunlight (like humans) so they must take it with food [2]. Both species are extremely susceptible to fatal poisoning (e.g. after eating a human supplement).
What it contains: Cod liver oil, fatty sea fish (salmon, herring, sprat, sardine, mackerel), to a lesser extent egg yolks and liver.
Deficiency: Causes rickets (in growing animals), osteomalacia (in adults) and “rubber jaw” syndrome. [1].
Excess: Stores in the body and is extremely toxic. It causes dangerous calcification of soft tissues (kidneys, heart, blood vessels). The security boundary is very narrow [3].
Sources
- National Research Council (NRC) (2006). Nutrient Requirements of Dogs and Cats, chapter 5 - fat-soluble vitamins. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
- How KL, Hazewinkel HAW, Mol JA (1994). Dietary vitamin D dependence of cat and dog due to inadequate cutaneous synthesis of vitamin D. Gen Comp Endocrinol 96:12-18. https://doi.org/10.1006/gcen.1994.1154
- Vecchiato CG, Delsante C, Galiazzo G et al. (2021). Cholecalciferol (Vitamin D3) Toxicity Observed in Five Cats. Front Vet Sci. https://doi.org/10.3389/fvets.2021.707741