Dealing with surplus experimental animals

Even with careful planning, the breeding of experimental animals will always produce animals that are not suitable for the planned animal experiment. The reason for this is that, for example, only animals of a particular sex or genetic disposition can be used for the experiment.

This is most clearly illustrated in the case of research on laying hens (only female animals), or genetically modified experimental mice that are bred to have a predisposition to certain diseases, for example, on which further research is to be conducted. This predisposition (technical term: “genotype”) is not always passed on to all offspring, however, with the result that some offspring are suitable as laboratory animals, but their siblings are not.

The “Understanding Animal Experiments” initiative explains this in its “Extended Statistics on Animals in Research” fact sheet with the example of so-called “knockout” mice.

Where possible, the University of Hohenheim prevents the birth of surplus experimental animals by taking the following measures:

• Purchase instead of breeding in-house: Where possible, laboratory animals with the desired characteristics are not bred in-house, but purchased from specialized breeders.
• Careful breeding planning: Including biometric planning to determine the exact number of animals required for an experiment or to maintain the breeding line.
• Cryopreservation: Mainly genetically modified rodent lines that will not be needed in the foreseeable future are cryopreserved. Instead of keeping live animals, sperm and eggs are stored frozen. This avoids unnecessary maintenance breeding, which inevitably results in surplus animals.

Despite all these measures, surplus experimental animals cannot be avoided. The uses of these animals include:

• Use as feed animals: So-called wild-type rodents, i.e. rodents that are not genetically modified, can be disposed of as feed animals. This also applies to farm animals (especially poultry) without targeted genetic modification, provided that there are no concerns under feed law. The law prevents genetically modified animals from being used in this way.
• Use for food production: Farm animals used for research at the University of Hohenheim are generally no different than their counterparts on the farm. Such surplus animals can also be used for food production. Of course all food hygiene requirements must be observed and documented. The law prevents genetically modified animals from being used in this way.
• Selling animals or giving them away: Legally, only animals that have not been genetically modified may be sold or given away to third parties. However, the law sets high hurdles for this: According to § 10 (1) of the Ordinance on the Protection of Animals Used for Experimental Purposes (TierSchVersV), the University of Hohenheim is required to verify that the animals’ state of health permits this, that the animals do not pose a risk to the health of humans or other animals or to the environment, and that suitable measures have been taken to ensure the animals’ welfare. To this end, programs must be in place to ensure the acclimation of the animals being accommodated (§10 (2) TierSchVersV).
• Use or re-use in research and teaching: Surplus animals can be placed in other research projects or used in teaching or training via the University of Hohenheim’s Animal Welfare Officer.
• Euthanasia of compromised animals: Genetically modified animals with a compromised phenotype are euthanized in accordance with animal welfare legislation as they can only continue to live with more than mild pain, suffering or harm (moral imperative).