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

Overview

• This research establishes reference intervals for essential serum macro- and microminerals in clinically healthy horses from Northwestern Spain.
• The study also examines how age, sex, breed, and diet influence mineral concentrations, highlighting diet as a significant factor affecting certain mineral levels.

Introduction and Purpose

• Serum mineral concentrations serve as important indicators of a horse’s nutritional status, metabolic health, and overall wellness.
• Despite their importance, contemporary reference intervals (RIs) for minerals based on large, well-defined populations are limited, which can complicate clinical interpretation.
• The objective was to establish reliable serum RIs for key macro- and microminerals in healthy horses from Northwestern Spain and to assess the impact of biological variables and diet on these mineral levels.

Methods

• A total of 211 clinically healthy horses were sampled, ensuring a sizeable and representative population.
• Minerals analyzed included macrominerals: calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), sulfur (S); and microminerals: cobalt (Co), copper (Cu), iron (Fe), iodine (I), manganese (Mn), molybdenum (Mo), selenium (Se), and zinc (Zn).
• State-of-the-art multielement analytical techniques were used to measure serum concentrations:
  • Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)
  • Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
• Statistical methods followed the Clinical and Laboratory Standards Institute (CLSI) C28-A3 guidelines to calculate reference intervals accurately.

Results

• Robust reference intervals were established for all tested macro- and microminerals, providing clinically relevant baseline values for this horse population.
• Biological factors such as age, sex, and breed had minimal influence on serum mineral concentrations, with overlapping values across groups, suggesting that separate reference intervals by these factors were unnecessary.
• Diet showed a significant effect on serum mineral levels:
  • Selenium (Se) concentrations were notably influenced by diet.
  • Horses grazing only on pasture had selenium concentrations often near the lower limits of the reference intervals.
  • Horses fed commercial concentrate diets showed higher, presumably more optimal, selenium levels.

Conclusions and Implications

• This study successfully provides comprehensive and reliable serum reference intervals for an important set of macro- and microminerals in healthy horses from Northwestern Spain.
• The findings emphasize the minimal impact of biological variables like age, sex, and breed on mineral status.
• Diet, particularly the type of feed (pasture vs. commercial concentrates), is a key determinant of certain mineral concentrations, with clinical relevance for nutritional management.
• These reference intervals serve as valuable tools for clinical assessments, helping veterinarians and nutritionists accurately evaluate mineral status, identify deficiencies or excesses, and tailor dietary recommendations.
• Moreover, the data enhances research capabilities on mineral metabolism and physiological health in equine populations.