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RIO
THE INSTITUTIONAL ANIMAL CARE AND USE COMMITTEE (IACUC)

IACUC / LARC STANDARD PROCEDURES

Oral Gavage in Mice (Posted May 2008)

Description of procedure:

Oral gavage (dosing) is used when a specific volume of an agent needs to be administered orally.  Whenever possible, alternatives such as purchasing custom-made chow containing the experimental agent, or dosing via a water bottle should be considered. Gavage may only be performed by trained personnel. 

Supplies needed:

  • 18-20 gauge feeding tubes with a rounded tip. If gavage is performed on young mice a smaller tube is used. 
  • Permanent marker
  • Scale

The maximum dosing volume is 10mls/kg.   Dosing may repeated up to 3 times within a 24 hour period – any dosing exceeding this must be justified in the protocol.  It is appropriate to weigh the largest and smallest mouse and use the average of those weights to calculate the maximum dosage for all animals in the same experimental group.
 
1. Check the length of the gavage tube by measuring from the tip of the animal’s head to the last rib. Mark the tube at the nose and do not pass the tube into the animal past that point to avoid perforation the stomach.  This is particularly important with younger animals (<20 grams).

2. Scruff the mouse, grasping the skin over the shoulders with the thumb and middle fingers. Grasp the skin over the shoulders so that the fore legs are extended out to the side, keeping the front feet from pushing the gavage tube away.

3. Gently extend the head back with the index finger placed on top of the head—this extension of the head creates a straight line through the neck and esophagus.

4. Hold the animal parallel to the work surface while placing the gavage tube in either side of the mouth, over the tongue. Advance the tube through the pharynx, gently pressing the gavage tube to the roof of the mouth to elevate the head and straighten the esophagus. Pass the tube smoothly in one motion.

Note: If there is any resistance, do not force the tube. Pull the tube out and try again.

5. After dosing, remove the tube gently following the same angle as insertion.

6. Return the animal to the cage and monitor for 5-10 minutes, looking for any sign of labored breathing or distress. Monitor animals again between 12-24 hours after dosing.

Literature search words required:

Literature search was performed for refinement of this Standard Procedure on January 14, 2008:

Key Words Search Site Years Covered
Oral gavage in rodents, oral dosing in rodents, alternatives to oral gavage in rodents Pubmed Full database up to May 2008
Oral gavage in rodents, oral dosing in rodents, alternatives to oral gavage in rodents Google Full database up to May 2008

Agents:

All agents administered to animals should be listed in the "Agents" section of RIO.

Adverse Effects:

Procedure, Agent or Phenotype Potential Adverse Effects Management
Oral dosing Perforation of esophagus or stomach euthanasia
Delivery of fluid into the lungs Labored breathing or any signs of  respiratory distress (pale mucous membranes, listlessness) euthanasia

Monitoring Parameters:

Monitoring Parameters Frequency PI/Lab will Document

General appearance/activity level

For 5-10 minutes after each dosing and 1 time within 12-24 hours after procedure. no
Describe the conditions, complications, and criteria (e.g. uncontrolled infection, loss of more than 15% body weight, etc.) that would lead to removal of an animal from the study, and describe how this will be accomplished (e.g. stopping treatment, euthanasia).

Distress (labored breathing, sudden lethargy, poor mucous membrane color) for mis-delivery.  Any animal with these signs will be euthanized.

For all investigators housing animals with tumor formation, skin lesions, neurological deficits, or that are in Category E, list the expected characteristics/clinical presentations and endpoints of the animal model and the criteria for euthanasia. Note: The IACUC also requires such lists to be posted in the respective animal rooms and monitored by the IACUC compliance staff and LARC, to assure PI adherence to the endpoints listed.