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

Overview

• This study evaluated how a large oral dose of iron affects blood iron levels in horses using an iron absorption test (IAT), a method typically used in humans but not previously tested in horses.

Background

• Iron absorption tests (IATs) measure how well iron is absorbed by the body, often used in human medicine.
• These tests had not been previously conducted in horses, so their effectiveness and response profiles were unknown in this species.
• Understanding iron absorption in horses is important because iron status affects health and proper supplementation needs to be monitored to avoid deficiencies or excesses.

Study Objective

• To determine how a large oral dose of iron (ferrous sulfate) influences several blood iron parameters over time during an IAT in horses.
• Specifically, the research sought to observe changes in serum ferritin, iron, total iron binding capacity (TIBC), and hepcidin before and after iron supplementation.

Methods

• Twelve mixed-breed gelding horses were given:
  • 2% of their bodyweight in mixed-grass hay
  • An iron-free vitamin-mineral supplement to control dietary iron intake
• Baseline IAT:
  • Horses received an oral dose of ferrous sulfate at 25 mg per kg of body weight.
  • Jugular venous blood samples were collected before dosing, and at 3, 6, 12, and 24 hours after dosing to measure serum iron parameters.
• After 28 days on the hay diet, horses were divided into two groups:
  • IRON group (n=8): received daily iron supplements
  • Control group (CTRL, n=4): stayed on the hay diet without added iron
• After another 28 days, a second iron absorption test (Supp IAT) was conducted using the same protocol as the baseline IAT.
• Blood serum was analyzed for:
  • Ferritin (iron storage protein)
  • Serum iron levels
  • Total iron binding capacity (TIBC) which reflects the blood’s capacity to bind iron with transferrin
  • Hepcidin, a hormone regulating iron absorption and release
• Statistical analysis:
  • Analysis of variance (ANOVA) was used to determine differences over time and between groups
  • Area under the curve (AUC) calculations assessed cumulative iron responses
  • Significance was set at P≤0.05

Results

• Baseline IAT:
  • Significant changes over time were observed in serum iron, TIBC, and hepcidin after the iron dose.
  • This confirmed the test could detect dynamic changes in iron parameters post-dose.
• Supp IAT (after 28 days of supplementation):
  • Significant time-dependent changes were seen in serum ferritin, serum iron, TIBC, and hepcidin, indicating an altered iron status.
  • Hepcidin responses were significantly higher in the IRON group compared to controls (P=0.01), suggesting increased regulation of iron absorption due to supplementation.

Conclusions

• The iron absorption test (IAT) is a simple and effective tool to evaluate iron absorption in horses.
• Iron supplementation appears to increase iron absorption following the test, even in horses that already have elevated iron levels.
• Increases in serum hepcidin after supplementation may reflect physiological regulation to prevent iron overload, showing the body’s response to increased iron availability.
• This research supports using IAT in horses for monitoring iron status and potentially guiding iron supplementation strategies.