How do I handle animals?

Proper restraint of animals is essential for facilitating research and providing humane care. Inexperienced persons planning to work with animals should arrange training in any aspect of animal handling. Submit a Veterinary Services Request Form (in pdf) indicating the type of training needed.

How do I euthanize animals?

Euthanizing animals can be performed by exposure to CO2. Place all animals in the chamber and saturate the cage with CO2 for 1-2 minutes for mice and 8-10 minutes for rats. Neonates must be decapitated for successful euthanasia. CO2 is an approved method for small animals only. Larger specimens must be euthanized with an overdose of a barbiturate. Overdosing is usually three times the anesthetic dose and is species specific.

How do I sex pups?

Pups can be sexed by measuring the ano-genital distance. Compare two mice until you can find a difference in distance. Females have a shorter ano-genital distance than do males. If you have difficulties determining sex, the veterinary staff is available to help you.

When do I have to wean?

Weaning must be done at 21 days of age to prevent unnecessary premature mating and provide a healthy uncrowded environment.

What do red and blue flags mean?

Flags on doors are placed by the husbandry staff when a problem is found within a room. Berg utilizes red flags and Skirball utilizes blue flags. The veterinary staff identifies the problem and reports to the contact person listed on the cage card. Cages with problems are identified by one of two cards.

Separate: overcrowded - weaning age, exceed cage limits, fighting.

Veterinary Services: fighting, ulcerative, dermititis, tumor.

Most resolutions for cages marked for Separate must be completed by the contact person within 72 hours. If not completed, the veterinary staff will separate and charge your department for the time. It is important for your research and humane care that you wean and separate on time.

Resolutions for cages marked Veterinary Services varies per cage. Usually animals are observed, treated if possible, or sacrificed.

How can I improve the breeding performance of my mice?

Some mice, including the C57BL/6J inbred strain, are very susceptible to environmental stress. Breeding difficulties may be overcome in this strain and others by examining the overall mouse room conditions and trying to minimize exposure to sudden noises, excess handling, and vibrations from equipment in adjoining rooms. Often, extending the light/dark cycle from 12/12 to 14/10 can improve performance.

As well, dietary fat content and nutritional makeup affects the overall health of the mice and also their reproductive performance. We have had success with mice maintained on breeder chow that is available through DLAR. Another factor to consider is that reproductive performance generally decreases with age. We recommend replacing older breeders (i.e., greater than 8 months of age) with young mice (i.e., 6-8 weeks of age) on a routine basis. If breeder pairs do not produce progeny within 6-8 weeks, try switching males and female pairs. If females are not caring for their young and environmental stress has been minimized, then consider fostering the litter to a proven surrogate mother.

How should I foster a litter?

Newborn litters are sometimes fostered onto nursing surrogate mothers for a variety of reasons. The following is a compilation of comments, suggestions and proven techniques that can be used to successfully foster a litter. It is important to note that techniques used to ensure the foster mother will accept the new pups vary and the method that works best may depend upon individual preferences and the reason for fostering.

• The first step in fostering is the selection of a suitable foster mother. Try to choose a mother that has successfully weaned a litter in the recent past. For best results it is important to match the age of the litter to be fostered with the age of the foster mother's natural litter. The foster mother’s litter should be a different coat color than the litter to be fostered so the pups can be separated at weaning. If, however, the entire natural litter is removed and replaced with the foster litter this is not necessary. Always be sure the foster mother has finished delivering her young before using her as a foster mother because sometimes one or two pups may be born up to 6 hours after the majority of pups are born.
• It is critical to have the foster litter size equivalent to the natural litter size. If the litter to be fostered is especially large (i.e., more than 10 pups) then the litter may need to be divided and given to two foster mothers. A change in litter size of ± 2 or more pups can affect the milk supply of the foster mother.
  • It is best to keep the foster mother in her cage, remove the natural litter, then add the foster litter to the cage. The foster mother and her foster litter can be transferred to a clean cage the next day. During the first 24 hours, avoid disturbing the foster mother and her new foster litter, but periodically check to ensure that the foster mother is caring for the new litter.
  • An alternative approach to transferring a litter is to remove the entire nest containing the foster mother's natural litter. Place the nest under a heat lamp or some source of heat. Next place the foster litter in the nest, then gently mingle pups from the natural and foster litters together to spread scent. Rub feces from the foster mother on the backs of the foster pups. When the foster mother cleans the foster pups, she will most likely accept the pups as her own. Place the nest with the foster pups back in the cage of the foster mother.