Influence of variable content of dietary zinc on copper metabolism of weanling foals.

This research assesses the impact of varying levels of dietary zinc on the copper metabolism of young, weaning horses. Notably, excessive dietary zinc negatively affected the balance of copper in these foals’ systems, leading to health issues that included lameness and a degenerative bone disease known as osteochondritis dissecans.

Study Design and Methodology

• The research focuses on studying the impact of varying amounts of dietary zinc on the bodies’ capacity of weanling foals to maintain a normal balance of copper. It tested four levels of zinc content: 29.1, 250, 1,000, and 2,000 mg/kg of dry weight, while maintaining a constant copper level of 7.7 mg/kg in the diet.
• Foals were closely monitored during the study, with the researchers checking serum copper and zinc concentrations. At the end of the study, terminal hepatic copper and zinc contents were measured.

Results

• The study identified that foals fed lower levels of zinc in their diet (29.1 and 250 mg/kg) were able to maintain normal copper and zinc concentrations in their blood for 14 to 15 weeks.
• However, foals consuming the higher-zinc diets became hypocupremic, displaying lower-than-normal levels of copper in their blood, within 5 to 6 weeks. This variously led to lameness and osteochondritis dissecans, a degenerative disease affecting the cartilage within joints.
• Measurements showed serum zinc concentration increased to greater than 2 micrograms/ml within 2 weeks for foals consuming the higher-zinc diets. These foals also began to show symptoms of lameness when their serum copper concentration remained at 0.3 micrograms/ml for more than a week. Lower figures were seen in lame foals at the study’s conclusion.

Conclusions

• The study highlights a significant negative effect of increased dietary zinc on the copper balance within a foal’s body. This imbalance can cause serious health effects, such as lameness and osteochondritis dissecans, a degenerative disease affecting the joints’ bones and cartilage.
• These findings point towards the significance of maintaining a balanced diet in weanling horses, particularly in regards to ensuring proper levels of zinc, to preserve their overall health and well-being.