Reference intervals for serum macro- and microminerals in clinically healthy horses in Northwestern Spain: Influence of age, sex, breed and diet

BACKGROUND: Serum mineral concentrations are key indicators of nutritional status, metabolic function and health in horses; however, contemporary reference intervals (RI) derived from large, well-characterised populations remain scarce. OBJECTIVES: To establish serum RI for macro- and microminerals in clinically healthy horses in Northwestern Spain and to evaluate the influence of sex, age, breed and diet on mineral status. METHODS: Blood samples were collected from clinically healthy horses (n = 211), and serum concentrations of essential macrominerals (calcium [Ca]; phosphorous [P]; magnesium [Mg]; sodium [Na], potassium [K] and sulphur [S]) and microminerals (cobalt [Co]; copper [Cu]; iron [Fe]; iodine [I]; manganese [Mn]; molybdenum [Mo]; selenium [Se] and zinc [Zn]) were determined using precise, accurate multielement techniques (Inductively Coupled Plasma: ICP-OES and ICP-MS). RESULTS: Reference intervals were established for all minerals in accordance with the clinical and laboratory standards institute (CLSI) C28-A3 guidelines. Biological factors (age, sex, breed) contributed minimally to variability in concentrations, with extensive overlap between groups, indicating partitioning was unnecessary. Diet significantly influenced the concentrations of several elements, particularly Se; pasture-fed horses had lower levels of this element, often close to the lower limit of the RI, than horses receiving commercial concentrate diets. CONCLUSIONS: This study provides robust serum RI for macro- and microminerals in horses, providing valuable data for clinical assessment, nutritional monitoring and research on mineral metabolism.