Commercial Hair Analysis in Horses: A Tool to Assess Mineral Intake?

The use of hair samples to assess the mineral intake of horses under practical conditions has recently been attracting increased interest. The aims of this study were to compare mineral analysis results in equine mane hair between three commercial laboratories and to determine the relationship between the mineral intake and mineral content in mane hair. Four warmblood horses (14 ± 3 years) were included in the study. Horses were fed hay ad libitum and a commercial mineral supplement to meet nutrient requirements under maintenance conditions. Mane hair from the hairline was collected with a sample length of 2 to 3 cm according to the respective laboratory guidelines to monitor the feeding period of the last 1 to 2 months. Minerals in mane hair were analyzed by three commercial laboratories using inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy and in feedstuffs using ICP-MS to calculate mineral intake. Hair mineral analysis showed that the results and their corresponding reference ranges widely varied among the three laboratories. The mean coefficient of variance ranged from a minimum of 10% for selenium (Se) to a maximum of 58% for iron (Fe). For example, Se supply (requirement, 1.17-1.28 mg/d; intake, 1.83 mg/d) was considered insufficient in all horses by two laboratories, whereas it was considered adequate by one laboratory. Intervariation of the same sample, as well as differences in reference ranges, was considerably high among the three laboratories. These results indicate that hair mineral analysis is not reliable for assessing mineral intake in horses.