Feeding Large & Giant Breed Puppies
Energy & Protein
Critical Recap: Supplementing with too much calcium or phosphorus can increase a dog’s susceptibility to diseases. Large and giant-breed dogs fed excess calcium are more likely to develop osteochondrosis.
Vitamin D is composed of a group of sterol compounds that regulate calcium and phosphorus metabolism in the body. There are two pro-vitamin forms of this vitamin.
- Vitamin D2 (ergocalciferol)
- D2 is formed when the compound ergosterol is exposed to ultraviolet radiation (UV Rays). D2 is found in many plants and the conversion is only possible in harvested or “injured” plants, not living plant tissue.
- D2 is only of significance to ruminant & non ruminant herbivores eating sun-dried or irradiated plant materials. D2 is used less efficiently than D3 by dogs.
- Vitamin D3 (cholecalciferol)
- D3 is of great nutritional importance to dogs, and they are dependent on getting it via dietary sourcing because they have limited ability to convert 7-dehydrocholesterol in the skin to chloecalciferol.
Vitamin D’s functions are intricately involved with normal calcium and phosphorus homeostasis in the body. At the site of the intestine, vitamin D stimulates the synthesis of calcium-binding protein, which is needed for efficient absorption of dietary calcium & phosphorus. Vitamin D affects normal bone growth & calcification by acting with Parathyroid Hormone (PHT) to mobilize calcium from bone and by causing an increase in phosphate reabsorption in the kidneys. <—- What does all that mean?! It means vitamin D’s actions in the intestines, bones, and kidneys creates an increase in plasma calcium and phosphorous, to the level needed for normal mineralization of bone.
Dietary sources of vitamin D3 for dogs are relatively low. Moderate amounts can be found in foods such as Atlantic mackerel, Atlantic herring, whole egg, turkey liver, beef liver, beef kidney, domesticated duck meat, and turkey heart. Fish liver oils and cod liver oil are two concentrated food sources of vitamin D.
Critical Recap: Vitamin D plays an important role in regulating calcium and phosphorous metabolism. A deficiency in vitamin D can impact bone mineralization and cause skeletal issues.