Trace elements such as iron (Fe), copper (Cu), and zinc (Zn) are essential dietary components that support a broad range of biochemical and physiological functions. Despite being required in trace amounts, disturbances in their homeostasis can lead to a wide range of health issues. Their assessment in biological matrices, including hair, in companion animals continues to be explored as a means of understanding nutritional status, environmental exposure, and pathological conditions. However, data for companion animals remain limited. This study evaluated the influence of selected individual (sex, age) and environmental (diet type, living environment) factors on Fe, Zn, and Cu concentrations in the hair of clinically healthy dogs and cats living in Bucharest, Romania. Elemental quantification was performed using ICP-MS following acid digestion. Median concentrations were compared using Mann-Whitney U and Kruskal-Wallis tests, and associations among elements were evaluated using Spearman's rank correlation with Benjamini-Hochberg correction (FDR 0.05) to control for false discoveries. Dogs exhibited significantly higher hair Fe (168.29 µg/g) and Cu (6.99 µg/g) concentrations than cats (57.67 µg/g Fe; 5.86 µg/g Cu), whereas Zn levels were similar between species (93.12 µg/g in dogs; 101.20 µg/g in cats). Sex, age, and diet type showed no significant influence on Fe, Zn, or Cu in either species. In contrast, the living environment significantly affected Fe levels: dogs kept outdoors had markedly higher Fe concentrations (312.21 µg/g) than indoor dogs (78.31 µg/g), and the same pattern was observed in cats (111.05 µg/g in outdoor cats; 40.52 µg/g in indoor cats), while Zn and Cu remained unaffected. All pairwise correlations among Fe, Zn, and Cu were positive and remained statistically significant after FDR correction. Zn-Cu demonstrated the strongest association in both species (ρ = 0.773 in dogs; ρ = 0.883 in cats), with cats showing overall stronger inter-element correlations than dogs. These findings contribute to the limited reference data on companion animal hair mineral profiles and highlight the potential value of hair analysis for exploring environmental influences and trace element interactions in dogs and cats.
Badea et al. (Tue,) studied this question.