Copper and zinc levels in the blood of thoroughbreds in training in the United Kingdom.

The concentration of copper and zinc in the blood and sera of over 300 Thoroughbreds in training was determined by atomic absorption between February 1979 and July 1981. The mean (+/- sd) concentration of copper in the serum of stabled Thoroughbreds (79 +/- 16 micrograms/dl) was significantly (P less than 0.0001) lower than that of those at grass (101 +/- 26 micrograms/dl), whereas the mean serum zinc concentration of stabled Thoroughbreds (170 +/- 54 micrograms/dl) was higher than that of those at grass (111 +/- 45 micrograms/dl). No such differences were observed in whole blood. There were marked differences in the mean serum copper and zinc concentrations in the blood of Thoroughbreds housed in different stables. Significant changes occurred throughout the year in the mean values from individual stables. However, there were no such changes in the mean values of the total population. The observed differences were probably caused by dietary variations. The results emphasise the need to establish reference values related to diet if copper and zinc levels in blood are to be used for interpretative purposes.