There are three broad areas which need to be considered when planning animal studies:

1. The suitability of the species or strain as a model of the target organism
2. The ethical issues surrounding their use: ‘choosing the right animal for the right reason’. The large increase in use of genetically altered lines has created increasing concern about the suitability of these animals as models of human conditions.
3. Characterisation of the animals. Items to be considered, in collaboration with the supplier, include:
   • Species, strain, line and phenotype (with an explanation of any genetic modifications)
   • Age, developmental stage, sex and weight
   • Stage of oestrous cycle and any previous breeding history
   • Any necessary pre-treatment (e.g. castration or ovariectomy) and those responsible for this
   • Name and address of the supplier/breeder, or, if wild-caught, the place, time and method of capture and transport
   • Health status (e.g. germ-free, gnotobiotic, SPF, conventional, vaccination status)
   • Re-use of animals, which should be justified and which may be regulated by national legislation
   • Any plans for release or re-homing, which may be regulated by national legislation

Collaboration with other internal or external laboratories should be considered, to reduce the number of animals needed, for example by sharing organs. Steps should be taken to avoid surplus animals, such as those in breeding programmes which prove to be too old, those which respond poorly to treatment (for example by showing a weak immune response) or which are otherwise unsuitable for re-use, re-homing or release.

Information on a large number of textbooks that describe the species and strains used in animal research is available in the TextBase database on this site. Examples include The Laboratory Mouse, The Laboratory Rat and The Laboratory Fish.

More resources

• Examples and references from ARRIVE 2.0
• Information on inbred strains of mice and rats
• Strategies to minimise genetic drift and maximise experimental reproducibility in mouse research 
• Mouse Locator, UK
• The Collaborative Cross panel of inbred mouse strains
• Nude mice - more than what meets the eye
• The Rat Guide
• Rat Behavior and Biology
• Ratbehavior.org
• The Macaque website
• Does age matter? The impact of rodent age on study outcomes
• Progressing the care, husbandry and management of ageing mice used in scientific studies (Wilkinson et al., 2019)
• Know thy mice: Variability in aged mice
• Gonadal sex and animal experimentation: Perfection vs. 3R principle? (Bie & Debrabant, 2020)
• Sex bias in preclinical research and an exploration of how to how to change the status quo (Karp & Reavey, 2018)
• Prevalence of sexual dimorphism in mammalian phenotypic traits (Karp et al., 2017)
• Study reveals how sex 'blindspot' could misdirect medical research
• Genetic enhancement of NSG and NRG mice for improved human disease modelling
• Special issue of the journal Animals with papers on animal emotion
• Report of the Federation of European Laboratory Animal Science Associations Working Group on animal identification (2013)
• Welfare and scientific considerations of tattooing and ear tagging for mouse identification (Roughan et al., 2019)
• A standardised framework to identify optimal animal models for efficacy assessment in drug development (Ferreira et al., 2019)
• Identification methods in newborn C57BL/6 mice: a developmental and behavioural evaluation (Castelhano-Carlos et al., 2010)
• Tickling rats for improved welfare
• Know Your Model: how essential is that essential gene?
• Charles River guide to strategies to minimise genetic drift and maximise experimental reproducibility in mouse research
• Janvier Labs webpage giving advice on customised strategies to breed and secure an animal model
• Know your Model: Why mouse inbred strain contribution matters (Perry et al., 2020)

• Refining rodent models of spinal cord injury (Lilley et al., 2020)