Establishment of the 2012 vitamin D requirements in swine with focus on dietary forms and levels of vitamin

In swine nutrition, little is known about vitamin requirements for reproductive processes and bone health, especially vitamin D. Supplemental vitamin D is usually added to animal feed as cholecalciferol (vitamin D3), which is transported to the liver and hydroxylated to 25-hydroxycholecalciferol (25(OH)D3), and this metabolite has become commercially available for swine nutrition. Recently, the official vitamin D requirement for gestating and lactating swine was increased from 200 to 800 IU vitamin D/kg feed. The purpose of the present paper was to review the main findings of a published study, which has contributed to the basis for this establishment, and to put them into context with the existing literature. In this study, a dose–response trial with 4 doses of both vitamin D3 and 25(OH)D3 was performed with breeding swine and consisted of 2 experiments: In Exp.1, 160 gilts from first estrus until d 28 of gestation were fed diets containing 4 concentrations of 1of 2 vitamin D sources (i.e., 200, 800, 1,400, or 2,000 IU/kg from cholecalciferol or corresponding levels of 5, 20, 35, or 50 μg/kg from 25(OH)D3 [Hy-D]). Concurrently in Exp. 2, the same 8 dietary treatments were fed to 160 multiparous sows from the first day of mating until weaning. Dietary treatments of ≥800 IU/kg feed showed beneficial effects for breeding swine in terms of bone mineral content and ultimate strength, decreased number of still born piglets, and greater vitamin D status in comparison with dietary treatments of 200 IU/kg of feed. In addition, using the Hy·D resulted in greater concentrations of plasma 25(OH)D3 when fed at equal amounts (weight) of vitamin D3 but depended on the level tested. Above 200 IU/kg feed, 25(OH)D3 resulted in greater concentrations in plasma than vitamin D3 and could as such been considered as an equivalent or even more advantageous dietary source of vitamin D. In conclusion, this study, together with other recently published studies, addressed the nutritional benefits of vitamin D dose and forms for gestating and lactating sows and their offspring in terms of vitamin D status, reproduction, transfer to the neonate, and bone health.