Copper, Zinc-Superoxide Dismutase Activity in Exercising Horses Fed Two Forms of Trace Mineral Supplements

Abstract 

Nine mature horses were used to evaluate superoxide dismutase (SOD) response to a low-intensity standard exercise test and the effect of copper (Cu) and zinc (Zn) supplement form on enzyme activity. The modified switchback experiment was conducted over seven 28-day periods. Horses were conditioned to perform an average daily workload of 3.93 kg∗km∗10⁻³ with a digestible energy (DE) demand of approximately 29 Mcal. Following a controlled Cu and Zn repletion-depletion diet sequence, horses were fed a diet intended to be marginally deficient in Cu and Zn with the minerals supplemented in either sulfate or organic chelate forms. Horses were then subjected to a standardized exercise test to enable evaluation of SOD activity during exercise and immediate recovery. In the final analyses, mineral contents of the experimental diets were significantly different (P < .05). The mean mineral concentration of the sulfate diet was 6.28 ppm Cu and 35.99 ppm Zn, while the chelate diet contained 23.62 ppm Cu and 90.67 ppm Zn. Even so, resting SOD activity was not altered by diet (1793.47 ± 323.00 U/g Hb for the sulfate diet, 1355.70 ± 148.32 U/g Hb for the organic-chelate diet), nor did SOD activity change in response to the low-intensity workout. The SOD activity was unchanged by feeding a Cu and Zn supplemented diet to horses fed to be in a mineral-deficient state. These exercise bouts did not appear to have a significant impact on SOD activity. Other types of oxidative stress should be considered when trying to evaluate the antioxidant responsiveness of this enzyme.

Keywords: Superoxide dismutase, Copper, Zinc, Supplement form, Horses