Vitamin D is an essential fat-soluble vitamin for dogs that is important for calcium absorption, bone growth, and immune function. Dogs cannot synthesize vitamin D from sunlight like humans, so it must be obtained through their diet or supplements. Vitamin D becomes activated through a process in the liver and kidneys to form calcitriol, the active form. A vitamin D deficiency can lead to thin and brittle bones or rickets in dogs, while too much can cause hypercalcemia and related issues. The AAFCO recommends 500 IU of vitamin D per kilogram of dog food.

1. Vitamin D & Your Pooch
Dr. Preethi Sudarshanie Dassanayake (B.V. Sc. , M. Sc., MBA)
Veterinary Teaching Hospital, University of Peradeniya
Sri Lanka

2. Vitamin D
 Is a fat-soluble vitamin.
 A steroid vitamin.
 An essential vitamin for dogs.
 Is a family of compounds that are derived from cholesterol.
 Commonly found in two major forms (Vitamin D2 & D3).
 D2 – Known as Ergocalciferol (found in plants).
 D3 – Called as Cholecalciferol (found in animal tissues).
 D2 & D3 are inactive and in the category of Prohormones.

3. Vitamin D activation pathway
 Humans obtain sufficient amount of vitamin D through exposure to direct sunlight.
 Your pet cannot synthesize this vitamin through exposure to the sunlight.
 You have to supply it with foods or adding supplements.
 Vitamin D absorb in the small intestine but in inactive form.
 cholecalciferol (D3) 25- hydroxycholecalciferol (In the liver)
 25- hydroxycholecalciferol 1,25-dihydroxycholecalciferol (In the kidney)
 1,25- dihydroxycholecalceferol is known as Calcitriol (active form of vitamin D)
 Excess vitamin D deposit in adipose tissue.

4. Functions of Vitamin D
 Promotes calcium absorption in the gut.
 Maintains serum calcium and phosphate level.
 Prevent from hypercalcemic tetany
 Proper bone growth and bone remodeling.
 Facilitating healthy bones and teeth.
 Improves muscle strength.
 Improves immune function.
 Reduces inflammation (anti-inflammatory).

5. Functions …..
 Blood pressure control.
 Blood sugar level control.
 Protection from cancers.
 Regulating genes.
 Maintaining cell health.

6. The Association of American
Feed Control Officials (AAFCO)
Recommendation - 500 IU of
Vitamin D Per Kilogram of Dog
Food
IU means International Units.
1 IU = 0.025mcg
500 IU = 12.5 mcg

7. Vitamin D deficiency
 Bones become thin.
 Bones become brittle.
 Misshapen bones.
 Rickets.

8. Vitamin D toxicity
 Hypercalcemia.
 Loss of appetite.
 Weight loss.
 Excessive thirst.
 Frequent urination.
 Drooling.
 Vomiting.
 Muscle weakness.
 Soft tissue mineralization.
 Lameness.
 Disrupt normal skeletal development (pups).

9. Sources
 salmon
 Mackerel
 Sardines
 Shrimp
 Egg yolk
 Cod liver oil
 Fortified milk
 Yoghurt
 Cheese
 Tuna
 Beef liver

10. THANKS
Photo courtesy- Google Image