Circulating Elements in the Bloodstream of Growing Foals: Focus on Heavy Metals and Bone Remodeling Across Growth Stages

Bone tissue undergoes continuous remodelling throughout the life of the individual, and growth is the most impacting phase. In fact, tightly coordinated processes of resorption, synthesis, and mineralization of the bone matrix under systemic hormonal, biomechanical, and metabolic control occur for variable periods of time across species. The horse is a fast-growing animal and for this reason identified as precocial. It was hypothesized that blood serum levels of minerals in growing foals at different stages of accretion may vary over time. This investigation aimed to assess the dynamics of circulating mineral and trace element levels in serum from weaning to 24 months of age. A total of 40 serum samples (8 foals × 5 timepoints, T0-T4) were analyzed for total metals and metalloids by ICP-MS/MS (US EPA 6020B method). Each sample was measured in duplicate; the mean of the two replicate values was used in all subsequent statistical analyses. Cadmium (Cd) was the only trace element exhibiting statistically significant temporal variation throughout the growth period. A marked increase (p = 0.005) in circulating Cd was observed between T0 (6 mo.) and T1 (7 mo.), followed by a significant decline (p = 0.020) from T1 to T2 (12 mo.). Despite this population-level trend, no individual foal showed statistically significant intra-subject changes over time. All other essential trace elements remained stable, indicating preserved mineral homeostasis during growth from 6 to 24 months. These findings suggest that while essential minerals maintain a steady physiological profile during development, cadmium displays a distinct temporal pattern that may warrant further investigation. The data underscore the importance of monitoring heavy metals even in low-exposure environments during sensitive developmental windows.