Abstract
Vitamin D insufficiency is associated with various disease processes. We determined whether consumption of a diet supplemented with HyD®, a 25-hydroxycholecalciferol (25(OH)D3) source, would safely increase plasma 25(OH)D3 concentrations in Golden Retrievers with low vitamin D status. We hypothesised that dietary supplementation with HyD® would rapidly increase and sustain plasma 25(OH)D3 levels in healthy Golden Retrievers with low vitamin D status compared with supplementation with vitamin D3. Of fifty-seven privately owned dogs recruited with written owner consent, eighteen dogs with low vitamin D status were identified and sorted between two groups to have similar initial plasma 25(OH)D3 concentrations, sex distributions, ages and body weights. Dogs of each group were fed a dry dog food supplemented with either 16 μg/kg of 25(OH)D3 as HyD® (n 10) or 81 μg/kg of cholecalciferol (D3) (n 8) for 4 months. Plasma 25(OH)D3 concentrations were determined monthly. A significant time effect (P < 0⋅001) and time by group interaction (P = 0⋅0045) were found for monthly determined plasma 25(OH)D3 concentrations. Dogs fed the HyD®-supplemented diet experienced a 40⋅5 % rise in plasma 25(OH)D3 values after 1 month (P < 0⋅001) and no change thereafter. Plasma 25(OH)D3 values of dogs supplemented with vitamin D3 did not increase (P > 0⋅05) and were less than values of dogs supplemented with HyD® (P = 0⋅044). With few exceptions, average haematologic, biochemical and urinalyses results remained within the reference range for both groups. Dietary supplementation with HyD® is sufficient to safely increase and sustain plasma 25(OH)D3 levels in healthy dogs.
Highlights
Vitamin D is essential for numerous metabolic functions in dogs and other species
Owners of dogs determined to have plasma 25 (OH)D3 concentrations less than 50 ng/ml were notified by phone or e-mail and offered participation in the second part of the study: a diet supplementation trial to evaluate the efficacy of vitamin D supplementation using a custommanufactured, dry-expanded diet (Table 1)
Dogs were excluded if they were younger than 2 years or older than 10 years, if they had underlying disease processes, were pregnant, lactating, or had pregnancy planned during the trial duration
Summary
Vitamin D is essential for numerous metabolic functions in dogs and other species. Unlike man, dogs are unable to use ultraviolet rays to synthesise sufficient vitamin D in the skin to meet their requirement[1]. Supplementation with excess vitamin D in the form of cholecalciferol (D3) did not improve plasma D status in privately owned dogs that were considered vitamin D insufficient[16]. Supplementing 25(OH)D3 rapidly improved plasma D status in research dogs[17]. The objective of the present study was to determine whether consumption of a diet using vitamin D supplemented as HyD®, a proprietary form of 25(OH)D3, would increase the plasma 25(OH)D3 of healthy dogs above that achievable with D3. Retrievers have a high lifetime risk for the development of cancers[22] This makes them an ideal subject for a study evaluating the improvement of insufficient vitamin D. We hypothesised that the plasma 25(OH)D3 of dogs fed a diet supplemented with a high but not excessive amount of vitamin D3 would not significantly increase. Plasma 25(OH)D3 status of each animal was evaluated using a high-performance liquid chromatography (HPLC) method[23] that was adapted for analysis of dog serum and plasma[16,17]
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