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

Overview

• This study investigated how levels of minerals and heavy metals in the blood change in foals from weaning (6 months) to 24 months old.
• It found that most essential minerals remain stable during growth, but cadmium (a heavy metal) showed significant changes over time.

Introduction and Background

• Bone is a living tissue that continuously remodels through processes of resorption (breaking down), synthesis (building), and mineralization.
• Bone remodeling is influenced by hormones, mechanical forces, and metabolism, and is especially active during growth phases.
• Horses grow quickly and are considered precocial, meaning they are relatively mature and mobile shortly after birth.
• Understanding mineral dynamics in foals during growth is important for ensuring healthy bone development and detecting potential toxic exposures.

Study Objectives

• To measure the levels of minerals and trace elements, including heavy metals, circulating in the blood serum of foals at multiple growth stages.
• To evaluate whether these levels change over time during critical growth periods (from weaning at 6 months up to 24 months).

Methods

• 40 serum samples were collected, representing 8 foals sampled at 5 time points labeled T0 through T4 (T0 = 6 months, T1 = 7 months, T2 = 12 months, continuing to 24 months).
• Samples were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS/MS), following the US EPA 6020B protocol, which is a sensitive and accurate method for detecting metals and metalloids.
• Each sample was measured twice (in duplicate) to ensure accuracy; the average of these duplicates was used for data analysis.
• Statistical tests were performed to check for significant temporal changes both at the population level and within individual foals.

Results

• Cadmium (Cd) was the only element to show significant changes over the time points measured.
• A marked increase in blood cadmium levels occurred between 6 months (T0) and 7 months (T1) of age.
• This increase was followed by a significant decrease between 7 months (T1) and 12 months (T2).
• Despite the overall population trend, when looking at each individual foal, no significant intra-subject (within individual) changes over time were detected, suggesting variability but no strong within-animal pattern.
• All other essential trace elements and minerals remained stable throughout the growth period (6 to 24 months), indicating consistent mineral homeostasis during development.

Interpretation and Significance

• The stability of essential minerals suggests that foals maintain tight regulatory control over important minerals necessary for bone growth and metabolic function.
• The distinct temporal pattern of cadmium variation is notable because cadmium is a toxic heavy metal with no known beneficial biological role.
• The transient rise and fall of cadmium levels could indicate exposure fluctuations or changes in absorption/excretion mechanisms during growth.
• This highlights the need for further studies exploring cadmium sources, metabolism, and possible effects on bone and overall health in young horses.
• Monitoring environmental heavy metals, even at low exposure levels, remains important during sensitive developmental windows to prevent potential toxicity.

Conclusions

• Growth in foals from 6 to 24 months is characterized by stable serum levels of essential minerals critical for bone remodeling and health.
• Cadmium behaves differently, showing significant but temporary fluctuations in circulating blood levels during this time.
• The findings underline the importance of monitoring heavy metals in growing animals to better understand exposure risks and protect bone development.