GROWTH AND SKELETAL DEVELOPMENT IN THE DOG IN RELATION TO NUTRITION -A REVIEW

Longitudinal growth of the appendicular skeleton in the growth plates and the adjacent metaphyseal area includes chondrocyte differentiation , proliferation, maturation, and hypertrophy in the physis and bone (r e-)modelling in the metaphysis. The rate and extent of longitudinal gr owth are regulated by interactions between biomechanical factors and e ndogenous growth regulators, i.e., systemic endocrine factors, and loc al para- or autocrine factors, that act on the growth plate chondrocyt es. The most important endogenous regulators of growth and skeletal de velopment are growth hormone (GH) and insulin-like growth factors (IGF s), and calciotropic hormones, i.e., parathyroid hormone (PTH), vitami n D (vitD), and calcitonin (CT). The biochemistry, synthesis, secretio n, target organs, and effects of these endogenous factors are reviewed , and the calcium homeostatic mechanisms, dietary intake, bone turnove r, and calcium excretion are discussed. Energy, protein, and calcium a re nutritional factors of great importance to (skeletal) growth. The e ffects of low and high dietary intake of these nutrients are discussed , especially with reference to longitudinal growth and disturbances in endochondral ossification.