Keynote Message

The synthesis of vitamin D (vitD) in the skin was demonstrated for many species such as human, rat, cattle, sheep, goat, guinea pig, rabbit, and recently for pigs and hens. In contrast to these species, cats and dogs are mainly dependent on dietary vitD sources (Dittmer and Thompson 2011). Vitamin D's relation to the regulation of bone metabolism and skeletal health is well known, but interestingly many non-skeletal tissues express the vitamin D receptor. This leads to the assumption that vitamin D's role is far beyond of what we already know about it. In human medicine, many diseases are linked to Vitamin D deficiency: cancer, autoimmune, infectious and cardiovascular disorders. Vitamin D is involved in cell differentiation and immunomodulatory aspects (Dittmer and Thompson 2011). Little is known about the role of vitamin D in the physiology of non-skeletal tissues in cats and dogs and only a few studies on this issue exist. However, these studies show that also in companion animal disorders, vitamin D metabolism is changed and shows abnormalities. However, the physiological role of vitamin D in companion animals is still very scarce and this talk tries to summarise some studies which will lead to a better understanding of vitamin D homeostasis in cats and dogs. The literature on vitamin D metabolism and a wide range of diseases in companion animals and humans is a high trend at the moment. The problem about many studies is to find the true reason of what is directly linked to the onset, the development, and the outcome of these non-skeletal disorders or if vitamin D is simply a marker for these diseases or the outcome of these diseases, respectively. Especially in humans there is a wide range of studies on the role of vitamin D in the aetiology of diseases or even mortality (Kupferschmidt 2012). In the focus of these studies is the role of the supplementation of vitamin D, especially in the development of infections, autoimmune diseases or neoplasms (Kupferschmidt 2012). Some studies now show the effect of vitamin D in the development and treatment of different diseases in dogs and cats. In addition, it is important to avoid over-supplementation of vitamin D, since there are some reports that it may cause hypercalcaemia (Mellanby et al. 2005; Wehner et al. 2013).

Key References

1.  Dittmer KE, Thompson KG. Vitamin D metabolism and rickets in domestic animals: a review. Veterinary Pathology. 2011;48:389–407.

2.  Kupferschmidt K. Uncertain verdict as vitamin D goes on trial. Science. 2012;337:1476–1478. http://science.sciencemag.org/content/337/6101/1476.long

3.  Mellanby RJ, Mee AP, Berry JL, et al. Hypercalcaemia in two dogs caused by excessive dietary supplementation of vitamin D. Journal of Small Animal Practice. 2005;46:334–338.

4.  Wehner A, Katzenberger J, Groth A, et al. Vitamin D intoxication caused by ingestion of commercial cat food in three kittens. Journal of Feline Medicine and Surgery. 2013;15:730–736.