Interrelationships Between Age and Trace Element Concentration in Horse Mane Hair and Whole Blood

The use of hair as a sample matrix to determine the mineral status of an animal has received a lot of interest. The objective of this study was to determine if the trace element content in horse mane hair changed with age when evaluated in a group of horses representing a large age range. As a second objective, whole blood trace element content was evaluated, and its relationship to mane hair trace element content, as well as age, were tested. Therefore, mane hair and whole blood samples were obtained from 59 horses, ranging from 2 months to 26 years in age, housed on the same farm. Mane hair samples were washed, and hair and blood digested and analyzed for 11 trace elements. Weak correlations (P < .05) between age and mane hair trace element content was detected for arsenic (r = 0.29), copper (r = -0.39) and selenium (r = -0.27). While the mane hair color did not affect trace element concentration, greater variability was detected in the black mane hair samples. This resulted in outliers that were removed from the final statistical analysis. However, data is presented to the reader both ways. Correlations were also detected (P < .05) between age and whole blood iron (r = 0.62), selenium (r = 0.76) and zinc (r = 0.47). This is similar to what has been reported in horses using serum or plasma. The trace element concentrations of mane hair and whole blood were not correlated (P > .05) in this study. However, the concentrations of trace elements in mane hair were higher than that of blood. Trace elements, specifically chromium and lead, that were below detection levels in the blood, were detectable in mane hair. This suggests that mane hair may be a potential means to investigate suspected exposure to excessive levels of trace minerals or heavy metals that are difficult to detect in blood.