How can a rat's body temperature be measured? - briefly
Rectal thermometry with a lubricated probe provides the most accurate measurement of a rat’s core temperature. Infrared devices can estimate surface temperature non‑invasively, but their readings are less precise than rectal readings.
How can a rat's body temperature be measured? - in detail
Accurate assessment of a rodent’s core temperature requires careful selection of method, equipment calibration, and consistent handling technique.
Rectal probe insertion remains the most direct approach. A lubricated, flexible thermistor (0.5–1 mm diameter) is inserted 2–3 mm into the anal canal. Measurements are taken within 10–15 seconds to minimize stress. Record the reading after the probe stabilizes, typically at 37 °C for a healthy adult. Use disposable sheath covers to prevent cross‑contamination.
Infrared thermography provides non‑contact surface readings. Position the animal on a heated platform at a fixed distance (10–15 cm) from a calibrated infrared camera. Capture images of the dorsal neck and tail base, regions where surface temperature correlates with core values. Apply a correction factor derived from simultaneous rectal measurements to convert surface data to core estimates.
Implanted telemetry devices offer continuous monitoring. Surgically place a miniature temperature sensor into the peritoneal cavity or subcutaneous tissue. Connect the sensor to a wireless transmitter that logs data at preset intervals (e.g., every 5 minutes). Verify sensor accuracy before implantation and perform regular post‑operative checks for signal integrity.
Ear canal thermometers can be used when rapid screening is sufficient. Insert a small probe into the external auditory meatus, ensuring contact with the tympanic membrane. Record the temperature after a stable display (usually within 5 seconds). This method yields slightly lower values than rectal measurements and requires validation against core data.
Axillary and ventral skin measurements are less reliable for core estimation but useful for trend analysis. Place a thin thermistor against the skin, secure with tape, and record after equilibration (approximately 30 seconds).
Key procedural considerations:
- Acclimate rats to handling for at least 5 minutes before measurement.
- Perform measurements at consistent ambient temperature (22 ± 1 °C).
- Use anesthesia only when required; inhalant agents depress thermoregulation, so record temperature after recovery if anesthesia is employed.
- Calibrate all devices daily with a certified reference thermometer.
- Document time, animal ID, and environmental conditions for each reading.
Choosing the appropriate technique depends on experimental goals: rectal probes for single, precise core values; telemetry for longitudinal data; infrared imaging for stress‑free, high‑throughput screening. Each method balances invasiveness, accuracy, and practicality.