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The objectives of this investigation were to evaluate the serum 25-hydroxyvitamin D [25(OH)D] concentrations in pigs of different age groups, to determine if 25(OH)D concentrations varied with season, and to assess the quality of vitamin D supplements used in swine diets from multiple commercial suppliers. Serum samples (n = 1200) submitted to a diagnostic laboratory for routine surveillance were assayed for serum 25(OH)D concentrations. A total of 45 vitamin D premix samples were collected, resulting in 90 assays completed. Of the 45 samples received, 23 were manufactured outside the United States and 22 samples originated from two US manufacturers.
In all age categories, 25(OH)D concentrations in numerous serum samples were lower than reference values. In the nursery, finisher, and boar age categories, there was a difference between the months of January and June. Mature animals had greater 25(OH)D concentrations than younger animals (in both January and June). When January submissions were compared to June submissions, serum 25(OH)D concentrations in the June samples were higher in nursery, finisher, and boar age categories. Grower pig values were, however, significantly higher in January than in June. When June submissions from confined herds were compared to submissions from pigs with access to the outdoors, in all age categories (excluding boars, which were not tested), serum 25(OH)D concentrations were significantly greater in outdoor pigs than in confined animals.
Although the vitamin D concentration varied in the supplement samples evaluated, no samples had vitamin D concentrations statistically lower than the labelled concentration of 500,000 IU per g. No differences between the country of origin or laboratory utilized for testing were detected. Depending on the month of sampling, differences were detected. Premixes collected had lower concentrations in the spring (February, March, and April), than those collected during summer months.
These results revealed that commercial swine may be deficient in serum vitamin D at varying times of the year, and feed-supplement concentrations may vary.
Arnold J, Madson DM, Ensley SM, et al. Survey of serum vitamin D status across stages of swine production and evaluation of supplemental bulk vitamin D premixes used in swine diets. J Swine Health Prod. 2015;23(1):28–34.