Abstract
Steller’s and spectacled eider populations have declined drastically in recent decades and were listed as threatened under the U.S. Endangered Species Act in the 1990s.1-2 Although serum chemistry values including enzyme assays have been used to evaluate the health and organ function of several species of birds,3 no reference values have been established for Steller’s and spectacled eiders. Therefore, we collected serum from captive eiders at the Alaska SeaLife Center in 2003 to establish reference ranges for clinically healthy captive birds on consistent diets. We measured alkaline phosphatase (ALKP, EC 3.1.3.1), gamma-glutamyltransferase (GGT, EC 2.3.2.2), aspartate aminotransferase (AST, EC 2.6.1.1), lactate dehydrogenase (LDH, EC 1.1.1.27), and creatine kinase (CK, EC 2.7.3.2) enzyme activities using a VetTest 8008 analyzer (IDEXX Laboratories, Inc.) and compared results among seasons and genders using the α-level of 0.05. Gamma-glutamyltransferase activity was not detected in the serum of eiders. Seasonal differences in mean serum enzyme concentrations were detected in ALKP for Steller’s eiders and in CK and AST for spectacled eiders. In January, male spectacled eiders had higher mean serum AST concentrations than females, but no other differences were detected between genders. Annual mean (±SD) concentrations were calculated when no seasonal or gender differences were detected. For Steller’s eiders, the mean (±SD) serum concentration of AST, CK, and LDH were 11.5 IU/L (±28.6 IU/L), 203 IU/L (±68.3 IU/L), and 1031 IU/L (±246 IU/L), respectively. For spectacled eiders, the mean (±SD) serum concentrations of ALKP and LDH were 199 IU/L (±157.9 IU/L) and 1222 IU/L (±1138 IU/L), respectively. A significant correlation between CK and LDH was found in both species. Electrophoretic separation into isoenzymes has been used to characterize the source of enzyme activity, and our findings to date suggest that CK in eiders separates into two main isoenzyme fragments, and that a third isoenzyme fragment may be present (Beckman Paragon Electrophoresis system, Beckman Instruments, Inc.). In the future, reference intervals of enzyme and isoenzyme activities will be used to evaluate the health and organ function of wild Steller’s and spectacled eiders as part of a cooperative research effort to determine the cause of their population declines.
Acknowledgments
The authors would like to thank the Alaska SeaLife Center Eider Research, Avian Husbandry, and Veterinary Services departments for their help with this project.
Literature Cited
1. Federal Register. 1993. Final rule to list spectacled eiders as threatened. 58(88): 27474–27480.
2. Federal Register. 1997. Threatened status for the Alaska breeding population of the Steller’s eider. 62(112): 31748–31757.
3. Hochleithner M. 1994. Biochemistries. In: Avian Medicine: Principles and Application. 223–245.
4. Ritchie BW, Harrison GJ, Harrison LR, eds. Lake Worth, FL: Wingers Publishing, Inc.