How to weigh rats? - briefly
Use a calibrated laboratory balance, placing the rat in a clean container or harness and subtracting the container’s weight to obtain the net mass. Ensure the animal is calm and the scale is zeroed before each measurement.
How to weigh rats? - in detail
Accurate measurement of rodent body mass is essential for dosing, health monitoring, and experimental consistency. The process requires a calibrated scale, appropriate containment, and standardized handling to minimize stress and error.
Equipment
- Analytical balance (precision 0.01 g) or platform scale (precision 0.1 g) calibrated before each session.
- Small, lightweight container (e.g., polypropylene cup) with a lid that can be quickly opened.
- Zero‑weight reference (tare) material, such as an empty cup, placed on the scale before each measurement.
- Cleaning supplies (alcohol wipes, disposable gloves) to maintain hygiene between subjects.
Procedure
- Turn on the scale and allow it to stabilize according to manufacturer specifications.
- Place the empty container on the platform, press the tare button, and confirm a zero reading.
- Gently transfer a single rat into the container; avoid grasping the animal by the tail to reduce movement.
- Close the lid briefly to prevent escape, then record the displayed mass.
- Return the rat to its cage, clean the container, and repeat the process for each additional subject.
Standardization
- Conduct measurements at the same time of day, preferably during the animal’s inactive phase, to reduce metabolic fluctuations.
- Maintain ambient temperature between 20 °C and 24 °C; extreme temperatures can alter body weight through dehydration or water retention.
- Use the same container size for all individuals to keep tare weight consistent.
Error mitigation
- Verify scale calibration with a certified weight before the first measurement of the day.
- Observe the animal for vigorous activity; if the rat is moving excessively, pause and allow it to settle before recording.
- Record any anomalies (e.g., urine spillage, fur loss) that could affect the reading and note them in the data log.
By following these steps, researchers obtain reliable weight data while minimizing animal stress and measurement variability.