Efficacy of an iron absorption test on assessing iron status in horses

BACKGROUND: Iron absorption tests (IATs) are used to evaluate iron absorption in humans. However, this testing has not been conducted in horses. AIMS/OBJECTIVES: The objective was to assess how a large dose of iron affects blood iron parameters during an IAT. METHODS: Mixed-breed geldings (n = 12) were offered 2% of their bodyweight (BW) in mixed-grass hay and an iron-free vitamin-mineral supplement. A baseline IAT (Baseline IAT) was performed, where horses received 25 milligrams per kilogram (mg/kg) of BW of iron (ferrous sulfate) orally. Jugular venous samples were taken before the iron dose, and 3-, 6-, 12-, and 24-hours (h) post-dose. Horses were on the hay diet for 28-days, then assigned to 2 groups: IRON (n = 8), where horses received a daily iron supplement, or control (CTRL, n = 4), wherein horses remained on the same hay diet. After another 28-days, a second IAT was performed (Supp IAT). Serum was analyzed for ferritin, iron, total iron binding capacity (TIBC), and hepcidin. GraphPad Prism (Boston, MA) was used for analysis of variance and to calculate area under the curve, with significance set at P ≤ 0.05. RESULTS: There were significant time effects (P < 0.05) on serum iron, TIBC, and hepcidin for the Baseline IAT. During the Supp IAT, there were significant time effects (P < 0.05) on serum ferritin, iron, TIBC, and hepcidin. Serum hepcidin responses were higher (P = 0.01) in IRON vs. CTRL. CONCLUSION: An IAT is a simple measure for evaluating iron absorption. Iron supplementation appears to potentially increase iron absorption post-IAT, even when iron status is already elevated.