Higher Vitamin D2 and 25(OH)D2, but Not Vitamin D3 Metabolites, in Bovine Plasma and Muscle from Grass-Based Finishing System, Compared to Concentrate

Meat and meat products are one of the largest contributors to vitamin D dietary intakes. Little is known, however, about how different animal husbandry practices and/or finishing diets might affect the vitamin D content of the animal. Therefore, this study aimed to investigate the effect of bovine finishing diet (grass vs. concentrate) on the 25(OH)D plasma concentrations of cattle and subsequent vitamin D content in beef. Cattle were fed grass (n = 7) or concentrate (n = 9) finishing diets for 15 weeks prior to slaughter. Bovine blood samples were collected at slaughter and plasma aliquots were stored (-80 C) until analysis. Beef top rump from each animal was chilled for an ageing period of 21 days, then homogenised and frozen (-80 C) until analysis. Bovine plasma samples were analysed for circulating 25(OH)D3, and 25(OH)D2 (nmol/L), and raw beef muscle (top rump) samples were analysed for vitamin D metabolites; vitamin D3, vitamin D2, 25(OH)D3 and 25(OH)D2 (g/kg), all by LC-MS/MS. Total vitamin D activity was defined: [vitamin D3 + (25(OH)D3 5) + vitamin D2 + (25(OH)D2 5)]