PSVIII-24 - Dietary vitamin D was associated with increased circulating vitamin D in dogs with no observable adverse effect up to 9,992 IU/kg dry matter.

Abstract:

Introduction: Adult dogs have been reported to benefit from circulating 25 (OH) vitamin D above 100 ng/ml in order to support optimal health. Although there is no consensus for optimum concentrations of circulating vitamin D it has been reported that circulating vitamin D is positively related to a reduced severity of disease, decreased disease risk, enhanced efficacy of treatment and overall positive disease outcome. This association does not prove causality. However, the positive effect of circulating vitamin D suggest that this relationship is not simply an association or a response to disease but reflects a causal supporting function of increased circulating vitamin D above that required for bone health. Understanding the relationship between dietary vitamin D and circulating vitamin D status is essential to progress in using dietary vitamin D to influence health and disease in the dog.

Materials and

Methods: Five groups of 8 adult dogs each were fed for 6 months according to AAFCO maintenance protocols to evaluate the influence of dietary vitamin D on circulating vitamin D concentrations and indices of health. Body weight was recorded and blood samples taken before being fed treatment foods. After initiation of treatment foods, intake was measured daily, body weight was measured weekly, and blood samples were taken initially, after 85 days of feeding and at the end of the study. The dry matter concentrations of vitamin D (IU/kg) were: 796, 3087, 5511, 7314, and 9992 in approx. 4,000 kcal/kg foods.

Results: There were no clinical signs of either deficiency or excess vitamin D. Normal circulating concentrations of hemoglobin, packed cell volume, albumin, total calcium, phosphorus and alkaline phosphatase were maintained in all groups. Circulating vitamin D increased in all groups except those consuming 796 IU/kg. All dogs consuming increased dietary vitamin D had increased concentrations of 25 (OH) D when compared to the control group consuming 796 IU/kg. Concentration of calcium increased in all groups with no difference in calcium increase associated with dietary vitamin D. There was no difference in the change in concentration of parathyroid hormone or ionized calcium in response to treatment. Vitamin D increased in a linear and quadratic fashion in response to dietary vitamin D concentration. This resulted in all the dogs fed 5511 IU/kg and above exceeding 100 ng/ml circulating 25 (OH) D.

Conclusion: Dietary vitamin D was positively associated with increased circulating concentrations with no observable adverse effects in dietary concentrations up to 9,992 IU/kg dry matter. This allowed all dogs consuming 5511 IU/kg and above to exceed the circulating concentration previously recommended for optimal health in dogs.