Speed positively relates to initial core temperature elevations in exercising hunting dogs with myoglobin as a...

To determine if activity associates with core temperature and biomarker changes in exercising hunting dogs.

A group of local, versatile hunting dogs participated in a single-day mock hunt trial consisting of 2 repeated runs separated by 15 minutes on March 4, 2024. Venipuncture for exercise biomarkers occurred just prior to run 1 and immediately after completion of both runs. Core temperature (ingested thermistors) and activity (collar-mounted Global Positioning System and accelerometer) data were recorded every minute.

18 dogs completed the trial (median age, 3.5 years). Myoglobin significantly increased at each time point, whereas lactate and creatine kinase were unchanged. There was variable significance associated with increases of AST, cortisol, and heat shock protein 70. Biomarkers failed to correlate with activity or core temperature. Core temperatures over time demonstrated a pattern in which near steady-state temperatures (median, 40.27 °C; range, 39.38 to 41.28) were reached at an "inflection point" occurring at a median of 19.5 minutes (range, 11.0 to 29.0) from exercise initiation. Analysis of activity and temperature until inflection revealed weak to modest positive correlations between speed and both and rate of temperature change (R2 = 0.31) and temperature differential (R2 = 0.38).

Myoglobin was the most sensitive biomarker of exercise but failed to correlate to activity. Faster speeds during initial exercise are associated with larger and faster increases in core temperature.

Myoglobin may act as a potential marker for subclinical exercise stress in dogs. Speed may be an important canine activity measure contributing to initial core temperature changes during exercise.