309. Equine Segmental Trace Elements Analysis: Stronger Temporal Trends in Tail v. Mane.

Abstract Analysis of essential and non-essential elements in hair is widely utilized. However, it is unclear if significant differences in element concentrations across segmental hair segments and between anatomical locations (mane vs. tail) in equids occur with health and exposure relevance. Additionally, equid-specific reference data are limited. Hair provides a time-integrated record of elemental incorporation as a continuously growing biomatrix. The objective of this proof of principle study is to evaluate segmental analysis of mane and tail for quantifying essential and non-essential elements within a single managed equine herd and to determine whether variation along hair segments provides a more detailed profile of health and exposure status. Full length mane and tail samples were collected from horses (n = 27; avg. age 13.9 yr) managed at the University farm. Horses had been housed at the facility for at least 365 days, maintained on similar diets (pasture turnout; daily grain ration). Mane and tail samples were segmented into proximal to distal sections, yielding approximately 9 samples per horse. Samples were processed to remove external contamination in a series of washes, freeze-dried for storage, segmented, and analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Sixteen trace elements were consistently detectable across samples, supporting the sensitivity of hair as a biomonitoring matrix. Many elements (12/16; 75%) exhibited proximal to distal increases (P < 0.001) in tail hair, indicating increasing concentrations along the length of the hair. In contrast, fewer elements (8/16; 50%) showed significant positive trends in mane hair, and these trends were generally weaker. Several elements (4/16; 25%; Fe, Al, Mo, As) demonstrated significant variation in tail but not in mane, highlighting greater sensitivity of tail hair to segmental changes. Significant differences in elemental concentrations were observed between tail segments; however, most elements concentrations in the mane were consistent across segmental regions. Tail hair may provide a more stable and sensitive matrix for detecting temporal changes in trace element incorporation. The observed proximal-distal increases in elemental concentrations support the concept that hair segments capture sequential periods of element exposure or incorporation, offering greater temporal resolution than whole-hair analysis. Differences between mane and tail may reflect variation in structure, composition, growth dynamics, environmental exposure, anthropogenic interventions, or elemental deposition patterns. Overall, these findings support the use of horse hair as a non-invasive, time integrated biomatrix and demonstrate that segmental analysis, particularly in tail hair, likely enhances the ability to detect temporal variation in element status. This approach provides a foundation for developing equid-specific reference data and improving long-term health and environmental monitoring strategies.