Dietary Vitamin D Supplementation during Early Growth is not Protective for Medial Coronoid Disease Development in Labradors

Abstract

Introduction: Medial coronoid disease (MCD) is a common heritable disease in young large-breed dogs and is characterized by fissures and/or fragmentation of the medial coronoid process (MCP), cartilage, and/or subchondral bone. MCD development has also been attributed to disturbed endochondral ossification. Vitamin D influences skeletal development and endochondral ossification by stimulating the terminal differentiation of chondrocytes and the mineralization of cartilage and the newly formed osteoid. The aim of this study was to investigate whether vitamin D supplementation of the standard puppy diet given to puppies after weaning can prevent the development of medial coronoid disease (MCD) by stimulating endochondral ossification, including terminal differentiation of chondrocytes, and mineralization of the cartilaginous template of the developing medial cornoid process (MCP). Animals, material and methods: A litter of Labrador puppies was on purpose bred by mating a dam and a sire with MCD; these dogs are known to produce offspring with MCD. The puppies received a diet supplemented with 50,000 IU vitamin D per kg as fed. Development of MCD was monitored by computed tomography (CT) and plain radiographs every two weeks, and post-mortem by microCT, necropsy, histology, and immunohistochemistry and compared with data from a previous study. Results and discussion: Vitamin D supplementation did result in increased plasma levels of 25- vitamin D and 1.25-vitamin D, but did not prevent development of MCD in growing Labradors. Instead, vitamin D supplementation resulted in increased collagen X staining ofthe MCP and irregular costal growth plates, demonstrating disturbed endochondral ossification. Conclusion: Vitamin D supplementation does not prevent MCD development. Other causes for MCD rather than relative vitamin D deficiency causing disturbed endochondral ossification are more likely.