Research Animal Resources (RAR) Policy and Procedures for Handling Overcrowded Rodent Cages [ 1]

Policy:

1. The number of animals in the cage should be no more than is consistent with the welfare of all animals in the cage.[ 2] Recommended spaces for commonly used group-housed animals are indicated in the table below obtained from the Guide for the Care and Use of Laboratory Animals (p 27).
2. 2. Current contact information must be on the cage cards. Investigators are responsible for updating this information. RAR uses this information to contact the laboratory if a cage is overcrowded.
3. Investigators are responsible for marking the birth and weaning dates on their breeding cages. Animals must be separated by the weaning date.
4. Laboratory personnel must break down an overcrowded cage by within 2 business days of being notified. However, a severely overcrowded cage must be separated within 4 hours. A severely overcrowded cage is one in which delay could result in harm, illness, or extreme discomfort to the animals in the cage.
5. 5. If RAR must separate the cage due to the lack of availability or action by laboratory personnel in a timely manner, a technical services fee will be charged to the job number on the census sheet.
6. Failure of a laboratory to respond to RAR requests to separate overcrowded cages, or removal of "Overcrowded" tape without separating the cage will be referred to the Institutional Animal Care and Use Committee (IACUC).
7. If at any time you think the animals require medical attention, place a clinical call.

Procedures for Severely Overcrowded Cages:

1. Severely over crowded cages are those in which there are twice the recommended number of adult animals in the cage[3] or in which pups are being trampled by cage mates.
2. If the cage is severely overcrowded, notify a supervisor at once for guidance. The animals must be separated within 4 hours. Use the contact information on the cage card to notify the laboratory immediately.
3. Record the name and phone number of the individual you contacted, the date and time, and whether you spoke with them or left voice mail.
4. Mark the cage with “OVERCROWDED” tape. Put the date, time and your initials on the tape.
5. If someone from the lab cannot be located within 4 hours, proceed with separating the animals and notify the supervisor. Males will be placed in separate cages from females.

Procedures for other Overcrowded Cages:

1. On Day 1, using the contact information listed on cage card, notify the laboratory that there are overcrowded cages that must be separated within 2 business days.
2. Record the name and phone number of the individual you contacted, the date and time, and whether you spoke with them or left voice mail.
3. Mark the cage with "OVERCROWDED" tape. Put the date, time and your initials on the tape.
4. On Day 2, if cages are still overcrowded, notify RAR supervisor, who will contact the laboratory to remind them of the policy and the need to take care of the cages. The supervisor also should record the same information as listed in step 2 of this section.
5. On Day 3, proceed with separating animals, and notify the supervisor. Males will be put into separate cages from females. Add all required information to the new cage cards and identification of which home cage these animals were separated from.

1. Approved by Johns Hopkins University Animal Care and Use Committee on: April 17, 2003; last revised February 1, 2008
2. Guide for the Care and Use of Laboratory Animals, NRC. National Academy Press, 1996. p27.
3. For example, a standard 75 sq inch mouse cage permits a maximum of 5 adult mice. Mice are considered adults at weaning age, usually at 21 days.
   
   

Recommended Space for Group Housed Mice and Rats

	Weight, g	Floor area/animal, in2		Height, in
Mice	<10	6		5
	Up to 15	8		5
	Up to 25	12		5
	>25	15		5
Rats	<100	17		7
	Up to 200	23		7
	Up to 300	29		7
	Up to 400	40		7
	Up to 500	60		7
	>500	70		7
Hamster	<60	10		6
	Up to 80	13		6
	Up to 100	16		6
	>100	19		6
Guinea pigs	350	60		7
	>350	101		7

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