Hi kmarron –
Vitamin D exists in two forms – cholecalciferol (D3, occurs in animals) and ergocalciferol (D2, found predominantly in plants). Most animals are capable of fulfilling a portion of their vitamin D requirements by producing cholecalciferol in their skin when exposed to sunlight – dogs can do this but they aren’t quite as efficient at it as people so this is why it’s important that they receive supplemental vitamin D in the diet. D2 and D3 are generally considered equally potent for most species, however I believe D3 is the more natural choice. My dogs get their vitamin D in whole food form only – I believe that whole foods are better assimilated by the body and less likely to result in toxicity so I avoid all vitamin supplements. My dogs get their daily dose of vitamin D3 from cod liver oil which has 400 IU naturally occurring vitamin D3 per teaspoon, cage free eggs with have about 50 IU vitamin D3 per egg, Kefir which has 100 IU per cup and beef liver which has about 50 IU vitamin D per 4 oz. Oily fish such as sardines, salmon and mackerel are rich in vitamin D as well. If you prepare a properly balanced raw diet there should be no need to add synthetic supplements.
