Objective: To determine whether older, otherwise healthy, client-owned dogs were deficient in glutathione or cysteine, compared with young healthy pet dogs.
Design: Cross-sectional study.
Animals: 35 healthy dogs between 7 and 14 years old (older dogs) and 26 healthy dogs between 1 and 3 years old (young dogs).
Procedures: In all dogs, erythrocyte reduced glutathione concentration and plasma cysteine concentration were determined by means of high-performance liquid chromatography.
Results: Median erythrocyte reduced glutathione and plasma cysteine concentrations were not significantly different between young (1.7 mM and 8.3 microM, respectively) and older (1.7 mM and 7.6 microM, respectively) dogs. Significant differences were also not identified when values for young dogs were compared with values for only those dogs>or=11 years old. Similarly, no differences were found between males and females overall or between males and females within age groups, although most dogs were neutered.
Conclusions and clinical relevance: Results suggested that otherwise healthy older pet dogs fed a variety of commercial diets do not have deficiencies in glutathione or cysteine, compared with younger dogs. Findings do not support the routine empirical use of antioxidant supplements, such as precursors of glutathione, to treat presumed circulating antioxidant deficiencies in older healthy dogs.