Serum 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D concentrations in adult dogs are more substantially increased by oral supplementation of 25-hydroxyvitamin D than by vitamin D.

We previously found a weak response in serum 25-hydroxyvitamin D (25(OH)D) concentrations when dogs were supplemented with oral vitamin D (D). In the present study, we determined the relative potency of oral 25(OH)D compared with D for increasing vitamin D status in dogs with low serum 25(OH)D concentrations. Four male and three female, 4-year-old, intact, lean, genetically related, Chinese-crested/beagle dogs were studied in a randomised, single cross-over trial.

Oral vitamin D supplementation at five times the recommended allowance marginally affects serum 25-hydroxyvitamin D concentrations in dogs.

Little is known regarding optimal vitamin D status in adult dogs. To date no studies on vitamin D supplementation for improving vitamin D status have been reported for adult dogs. The aims of this study were to identify dogs with low vitamin D status and evaluate an oral dosage of cholecalciferol (D3) for effectiveness in increasing vitamin D status.