Hi Molly,
There is no science out there yet that I have read that feeding your dog fresh fish can cause a vitamin deficiency. I guess maybe if all you did was just feed them fish than I can see the concern. Molly is that what you are asking? That only feeding them fish will cause a vitamin deficiency?
Although one interesting article I read was regarding the Alaskan Eskimos and that they solely fed their sled dogs frozen fish and seals. Most lived to a fine ripe age. So who the heck knows dogs can thrive on anything. Ha
