Mouse work

1.) General remarks:

Scientists, who own cages, have to run their colonies by themselves. They have to set up matings and to wean pups, they have to do the genotyping and to take care of sick mice etc. Therefore running the colonies by “remote control” is not possible, which means regular physical presence in the animal facility is required. In case of absence (vacation, sickness etc.) a designated substitute has to take care of the colonies.

Please run your colonies carefully. Make sure that you find somebody who takes care of your colonies in case you are absent. We highly depend on your compliance with the IMP IMBA animal facility rules and the Austrian laboratory animal act. Every mistake may lead to a complaint by the authorities and as worst case scenario to the loss of the institute’s permission running a laboratory animal facility. Therefore please understand that repeated violation of the IMP IMBA animal facility rules will lead to the loss of the permission to enter the animal house.

Please never forget that you are dealing with live mice. Treat the animals in a respectful and gentle way; they are not inanimate laboratory devices. A huge workload must not lead to careless handling of animals.

Normal working time for the animal house staff finishes by Friday noon. Over the weekend there will be service (1 technician) just for maintenance and basic husbandry work with very limited capacity for additional work (e.g. plug checks).

2.) Guide to running your colonies:

  • During regular handling only one cage at a time should be managed. This will prevent accidental exchange of animals from different cages.
  • Animals that have escaped or dropped to the floor must never be returned to the suspected cage. Animals caught outside the cage should be isolated, if identification is possible, otherwise killed.
  • Cages and hoods should be in sufficient condition that no animal can escape or enter another cage (above all filter-tops are affected).
  • Please consider, that cages with filter tops are not stackable, because the filter sheet for the air exchange is not big enough and it is likely that the mice get problems of the impeded intracage airflow. Never leave mice in cages without filter tops.
  • Cages (individually ventilated cages as well as filtertop cages) must not be stored outside appropriate positions in the racks. They may be taken out and placed on a table just for doing the mouse work or in case of mice which have been ordered from our breeding room. As for IVCs the air supply will stop once the cage is removed from its position in the rack. Therefore individually ventilated cages always have to be placed in the proper rack position, please always make sure that the cage is locked in place, when you put it back into the rack. Never leave cages on the work bench overnight.
  • The adjustments at the control panel of the ventilator towers must not be changed. The ventilator towers must not be unplugged.
  • Cage cards should always be filled out properly, including the strain name, number of mice, gender, identification numbering of the animals in the cage, date of birth, in case of experimental use the name and the number of the experimental form where the appropriate project license is cited etc. Cagecards have to be considered as legal document. Everything which is written on a cagecard should be legible therefore. The contents of the cagecard mirrors the contents of the cages.
  • If a cage card is lost, you should not redefine the cage except in the case of definite proof of identity through marked animals within the cage.
  • Please avoid overcrowding of cages, there is a maximum number of mice, depending on the body weight and type of cage, which must not be exceeded per cage.
  • Never leave a cage without cage card, when you still need this cage, not even for a very short period of time. A cage without a cage card means, that you do not need the mice inside the cage any more and that they are supposed to be killed. This will be done by the animal house staff within 24 hours (immediately –-> one day later) during the week, but it can take some days over the weekend.
  • Never mix mice, which should be killed and which originate from different cages in one single cage (this is huge stress for them, perhaps they will fight) and never overcrowd those cages. Never leave pups, which are supposed to be killed, without their parents. The fact, that mice are supposed to be killed because you do not need them anymore, must not lead to careless handling and torture for the animals.
  • If at weaning the number of animals is larger than that recorded at birth the whole litter should be discarded or submitted to genetic monitoring.
  • Any change in phenotype and/or in productivity should be considered suspect for a possible genetic contamination (above all the change in productivity).
  • Never store black plastic bags with dead mice in the animal room or in the corridors. This endangers the health status of our mouse colonies. Put them into the fridge between the airlocks.
  • Please carefully check waste cages whether ther are no live mice inside any more. Always make sure that there are no live mice in a cage which is put out of a room. Used cages on the trolleys in the corridors will be considered as dirty stuff which is not used any more and will be put out to the washing kitchen. If there are hidden mice in the waste cages the cleaning staff will not be able to detect the. Everything which is in a cage will be diposed into a conveyer system, which will kill animals in a very painful way.
  • When mice from foreign institutes should be introduced into our animal house, or when mice should be sent to foreign institutes, please contact the animal house staff before (animaltransfer(at) We will take over the organization of the shipment. Otherwise the danger is very high, that mouse shipments get stuck at the airport, since the border veterinarians will not give the permission to enter into Austria or the country of destination without the appropriate documents. Therefore please do not organize shipments by yourself.
  • In case you want to order experimental diets please contact the animal house staff (Email: mouseorders(at) We will forward your order to the purchase department (special diets, which cannot be autoclaved have to be  irradiated).
  • If you do not need litters any more (pups which are supposed to be killed at weaning) please separate the breeding pairs. Producing mice over a long period, which are not needed apparently is not allowed.
  • Tail biopsy as tissue sampling method for genotyping is considered as laboratory animal experiment and therefore only allowed within a project license.
  • Sick mice/mice with impaired health status: According to Austrian law it is not allowed to keep animals, which are sick, suffer from pain, impairment of the locomotor system etc. These mice have to be treated (when it is likely that treatment will be successful) or euthanised. The decision has to be made by the veterinarian in charge. There is one exception to the rule concerning mice, which are used for an animal experiment based on a valid project license. In that case mice have to be treated according to the project license. If the disease is part of the project (expected) then it has to be described in the project license. Before approval the authorities will define the degree of distress and pain which will be acceptable, depending on the expected scientific value of the project. Depending on the scientific value so called humane endpoints will be defined. An animal which is subject to such project has to be killed when reaching the defined humane endpoints. (Checklist for animals´ health status)

3.) Acceptable effective ways to mark mice and simultaneous tissue sampling for genotyping (Identification of mice):

Permanent identification of laboratory mice is often a problem, since mice are very small and identification-systems, which are successfully applied in bigger animals are of limited value in mice. Because of the high reproduction rate of mice, the identification system has to provide a huge number of different codes. Identification systems should be legible and easy to apply even a few days after birth (> 5g body weight). In most cases a permanent and unmistakable marking is required. It is unavoidable, that even the tight fixation is stressful for the animal, but the procedure of identification itself should not cause too much additional stress. The impairment of the well-being of the animal should not last longer, than the duration of the identification procedure. It has to be considered carefully, whether anesthesia makes sense or not. In most cases the application of anesthetics causes more stress, than the identification procedure itself.

Since identification is not seen as a procedure by the Austrian Laboratory Animal Act 2012, two long-term identification methodes can be used for simultaneous tissue-sampling for genotyping without a special license:

- Phalanx distalis amputation (former toe-clip)

- Ear punches/Ear notches


Short-term identification:

Fur clips and color markers: In case of color markers it has to be considered, that non – toxic products are chosen, since the animals will intake the color by grooming and swallowing it. Besides the skin should not be irritated. One single operator can carry out this type of identification, it is cheap, easy to handle and the impairment for animal well-being does not last longer than the procedure. Identification at first glance is possible. It is a disadvantage, that it does not provide a permanent identification system.


Long-term identification:

Tattooing of footpads, tail etc.: Paw tattooing by color-spots: this can be done with or without special equipment: ink for tattooing, 1 ml syringe and 27G needle are required at minimum. A very small amount of ink is injected intracutaneously. A sufficient number of codes are provided, one single operator can carry out the procedure. Stress for the animals will be minimized, if trained personnel conduct it. Identification of the animal at first glance is more or less possible. It is an additional advantage, that it can be applied even in 5 days old (sometimes even younger) mice, it is cheap and permanent and no anesthesia is required. Several different tattooing systems (e.g. tail tattooing with numbers) are commercially available: these systems can be very expensive (€ 7,000 – € 9,000), because the price includes the high costs for training and education of operators.

Phalanx distalis amputation (former toe clip): According to the recommendations of the responsible authorities, identification of young mice and simultaneous tissue sampling for genotyping is possible under certain conditions:

  • optimum on day7 (day4 - day8 is acceptable)
  • amputation of the most distal phalanx only
  • maximum 2 toes/animal
  • maximum 1 toe/paw
  • to be performed by trained personnel only


Ear punches, ear notches: ears are marked with notches, `V´ or `VV´ cut by scissors or marked with punches by simple forceps-punchers or pliers. Identification of the animal at first glance is more or less possible. Anesthesia is not required and the procedure needs one (sometimes two) operator(s), it is easy to apply. Although it is inconvenient for the mouse, no bad consequences (impaired wound healing, infections, bleeding) may be expected, there will be no impairment of the animal´s well-being after the procedure is completed and the method is cheap. The system is restricted to older mice (> 14 days). Sometimes the code cannot be read properly later, when the procedure was done too early, because of the animal growth (the ears become longer and the position of the mark changes therefore). This system offers only a limited number of codes and has to be carried out only by experienced staff, since the animal has to be fixed tightly. The collected tissue can be used for genotyping.

Metal ear tags: Tags can be fixed at the pinna of mice by special pliers. The lightest and smallest tags should be used. Commercially available tags for the identification of fish (fish-tags) are recommended. One or two operator(s) should carry out this procedure, it is easy to perform, a huge number of codes are provided and anesthesia is not required. There is only a short moment of pain for the animal, when the tag pierces the ear. Quite often the tag leads to an irritation of the affected ear afterwards (local inflammation, which can last up to 14 days). The movement of the tag can cause holes of a diameter of about 3 mm in the ear. This identification is restricted to older animals. Sometimes the tags are lost. Since the tags are very small, it is difficult to read the number on the tag.

Electronic tags (currently not available in our facility): these systems require implantable encapsulated transponders and scanners. The transponders are implantated subcutaneously by using a special implanter with a 12G needle. The size of the transponder is about 5 mm x 2 mm. This system provides an endless number of codes, additional information can be recorded together with the code, the data can be imported directly into your computer system, and it is failsafe to a high extent. The impairment of animal well-being does not last longer than the procedure itself. One single operator can carry out this procedure. Because of the size of the transponder and the 12G needle, it cannot be used in very young mice (< 20 days. The price of the system (scanner and software) is high. Because of the high reproduction rate of mice a huge number of transponders (< € 7 per transponder) will be needed. Identification of the animal at first glance is not possible, a scanner is needed.The recommendation of one single identification system as the best of all is not possible. In almost all cases a combination of several systems is used. If the gender of the animal and perhaps the cage with the cage card, where the animal or the group of animals are housed, are included as additional identification feature, it should be possible to establish a system, which is failsafe, easy to read and which provides a sufficient number of codes. By choosing the appropriate system, it has to be considered among other features as costs, simplicity of the procedure etc., that the impairment of the well-being and stress for the animal has to be kept as low as possible.




4.) Ordering mice:

Inhouse bred mice: In case you want to order inhouse bred mice please contact the animal house staff, which means you have to send an email to < mouseorders(at) >. There is a small amount of standard mouse strains available, bred by the IMP IMBA animal house and there is a stock list, which is renewed every Wednesday, which will show what we have on stock. IMP IMBA bred stock mice will be put to your animal room within 72 hours. Although in general we try to provide you with the mice much earlier we cannot guarantee, that the mice are delivered immediately. This has to be taken into consideration, when planning an experiment, where you need mice. We cannot provide you with pre-weanlings.Once the mice have been transferred from our breeding room to the room of final destination an email will be sent to consignee confirming that the mice are delivered. Then you have to put the cages with the ordered mice into the allocated rack positions within the next 24 hours.

In case the required mice are not available by the IMP IMBA animal house, we will order those mice for you and get them from commercial breeders (Charles River, Taconic, Harlan, Janvier Elevage, JAX etc.).

Mice from commercial breeders: Because of organizational reasons the order has to be forwarded to the IMP IMBA purchase department by us since we have to inform the veterinary inspectors, we have to make sure that the healthstatus is compatible with our colonies, we have to make sure that the mice can be accepted etc. It saves time if your order can be forwarded directly by us (no open questions).

Therefore please tell us exactly the number of animals, gender, age, background strain, supplier etc. In case of JAX orders it helps if you tell us the stock number, or if you let us know the link to t the appropriate web site. The purchase department will place oders of  JAX mice always with Charles River. This company is the official agent of JAX animals in Europe, although they sell their original Charles River animals in addition. According to the availability it will take from one week to several months till the mice will be delivered.