The best source of Vitamin D is the sun. Lack of vitamin D has been linked weakened bones and a recent study of adolescents showed a lack of Vitamin D increased overall body fat and decreased amounts of the fat in the abdomen - a type of fat known as visceral fat, which has been associated with; heart disease, stroke, diabetes and hypertension.
So to increase you and your pets Vitamin D, is another great reason for you both to get outside and exercise!