Serum erythropoietin concentration is higher in healthy brachycephalic dogs than nonbrachycephalic dogs acclimated to 1,535 meters altitude

Objective: To assess the relationship between PaO2 and erythropoietin (EPO) concentrations and between PaO2 and hemoglobin (Hgb) concentrations in healthy brachycephalic (BRACHY) and healthy non-BRACHY dogs acclimatized to an altitude of 1,535 m. The third objective was to validate a human ELISA EPO kit for canine EPO measurement. Methods: Dogs were enrolled prospectively from January 2025 through September 2025. Venous samples for CBC, serum biochemistry, and EPO measurement were collected from a peripheral vein, and arterial samples were collected from the dorsal pedal artery. A human EPO quantitative ELISA was validated via spiking with recombinant canine EPO and establishment of linearity under dilution with 18 convenience samples. Results: 22 healthy adult BRACHY dogs and 32 healthy adult non-BRACHY dogs were enrolled. There was no correlation between PaO2 and EPO in any group. A moderate negative correlation was identified between PaO2 and Hgb among all dogs and for BRACHY dogs alone. Erythropoietin concentrations were significantly higher in BRACHY dogs compared to non-BRACHY dogs. Conclusions: Analytical performance of the ELISA kit was deemed acceptable. The results of this study highlight that more research is required to better elucidate the physiologic adaptations of dogs in conditions of hypobaric hypoxia or with chronic hypoxia due to BRACHY conformation. Clinical Relevance: EPO concentrations are significantly different between BRACHY and non-BRACHY dogs; however, the relationship between EPO, PaO2, and Hgb in these groups remains unclear.