During the past decade, many research studies have been devoted to how trace minerals affect horse health. Outcomes of many of the studies reveal that certain trace minerals are essential especially in young horses and broodmares. Two minerals that have been found to be important to horse health are copper and zinc.
Trace minerals in horse health
The use of copper and zinc supplementation in modern horse feeds stems from the possible role of these two nutrients in reducing physitis, osteochondrosis, wobbler syndrome, and other developmental orthopedic diseases.
In studies the role of an enzyme "lysyl oxidase" in the formation and maturation of cartilage has stimulated interest in copper as it relates to developmental orthopedic disease in young horses.
Additionally, zinc has long been known to play a role in the maintenance of epithelial integrity and keratogenesis.
The use of copper and zinc supplementation in modern horse feeds for all classes of horses stems from the possible role of these two nutrients in reducing physitis, osteochondrosis, wobbler syndrome, and other manifestations of developmental orthopedic disease.
It is interesting to note that in addition to its role in cartilage and bone metabolism, copper is involved in hemoglobin formation and in nerve conductivity and coordination. Copper is also involved in other enzymes such as tyrosinase and cytochrome oxidase to name but a few of the more well known of the enzymes.
A small loss of copper in the sweat of horses may result in sweat losses of 80-100 mg of copper per day.
In studies, zinc deficiency has resulted in reduced insulin levels and reduced glucose tolerance along with increased insulin resistance especially in the peripheral tissues. There has been a noted decrease in glucose utilization in zinc-deficient animals with a concomitant increase in fat catabolism.
In terms of bone metabolism, zinc deficiency directly inhibits the effectiveness of somatomedin in stimulating cartilage growth, and the classical symptom of zinc deficiency is disrupted keratogenesis.
A significant amount of zinc—about 20-21 mg/l—is lost in sweat. In the hard-working horse, this zinc loss can be substantial.
High levels of calcium and copper can reduce zinc absorption, so the kind of hay being fed may have an impact on the amount of zinc required by the horse. Increased levels of protein or increased protein intake have been shown to reduce zinc absorption and increase zinc excretion.
These classic and well-documented physiological and biochemical functions of zinc along with the relatively high zinc losses in the sweat have resulted in the development of more liberal allowances for zinc for performance horses.
Studies also show that when the efficacy of hoof supplements is considered, the inclusion of zinc methionine along with biotin and 3 grams of methionine appears to result in greater growth of the stratum germinativum and the tubular horn of the hoof wall than does the feeding of biotin alone.