Dr. Bonnie Mallard discusses vitamin D needs and deficiency rates among certain animals, and why it’s important.
Dogs can’t get much vitamin D from sunlight because their hair covers their skin. They used to get D from eating the organs of animals they hunted. Now, they’re getting the same diseases as humans, because of vitamin D deficiency.
I would add: Vitamin D laboratory blood tests say 100-150 ng/ml is the normal range for dogs. Most dogs are probably severely deficient, perhaps at 10-20 ng/ml, below even the normal range (30-100 ng/ml) for even humans.