Concentration of Selected Essential and Toxic Trace Elements in Horse Hair as an Important Tool for the Monitoring of Animal Exposure and Health

SIMPLE SUMMARY: Heavy metals pose a serious risk to the normal functioning of living organisms. Long-term exposure to heavy metals may lead to many pathologies and various dysfunctions. On the other hand, heavy metals are components of many enzymes, so any anomalies in their concentrations are not desirable. The main purpose of the study was to analyse the concentrations of selected essential and toxic trace elements in the hair of sports and recreational riding horses from studs located in central Poland. We also measured the concentration of heavy metals in oats used as the basic component of the equine diet to investigate the interactions between the elements in the feed and hair. Assessment of essential heavy metals is important for the monitoring of exposure and the health of horses. The study confirmed many significant relationships between the concentrations of elements in the hair and oats, as well as interactions between the content of these xenobiotics in feed and the analytical matrix. ABSTRACT: The main purpose of the study was to analyse the concentrations of selected essential and toxic trace elements in the hair of sports and recreational riding horses from studs located in central Poland and thus test the usefulness of this matrix for monitoring the exposure of these animals. We also measured the concentration of heavy metals in oats used as a basic component of the equine diet to investigate the interactions between these elements in the feed and hair. The basic chemical composition of oats was analysed. Elemental analysis was performed using an EcaFlow 150 GLP electrochemical analyser with an E-104L electrode and reference to a calibration curve. The chemical composition of oats was investigated by near infrared transmission (NIR) spectroscopy calibrated for an artificial neural network (ANN) using a Foss InfraXact spectrometer. Among all elements, the coefficient of variation was highest for Pb and lowest for Cd, regardless of the study group. The content of elements in horse hair was in the range of 153.56 to 185.79 mg·kg(−1) for Zn, 6.10 to 11.99 mg·kg(−1) for Cu, 0.578 to 0.813 mg·kg(−1) for Pb and 0.011 to 0.015 mg·kg(−1) for Cd (in kg of d.w.). For hair, we found a significant negative correlation for Zn-Cu (r(xy) = −0.539) and Cd-Cu (r(xy) = −0.676) at p ≤ 0.05. For feed, there was a highly significant positive correlation for Cu-Pb (r(xy) = 0.723) and Zn-Cd (r(xy) = 0.714) at p ≤ 0.01. We found significant negative oats–hair interactions for Cu-Zn, Pb-Cu, Cd-Cu and Zn-Pb, and a positive oats–hair interaction for Cu-Cu.