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NC3Rs: National Centre for the Replacement Refinement & Reduction of Animals in Research
Office-led project

Breeding and colony management

White icons of three mice on a blue background. Two female mice on the left hand side are each crossed with the same male mouse on the right side, indicating how different mice can be paired for optimised breeding.

At a glance

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  • Reduction
  • Refinement


The use of genetically altered animals has become a mainstay of biomedical research, with new technical approaches (e.g. CRISPR/Cas9) to manipulate the expression of genetic components evolving rapidly. Generating a genetically altered strain of mice uses large numbers of animals to create a colony, and to maintain a colony from which experimental animals are produced. Following best practices for colony management can help minimise the number of surplus animals used in breeding colonies, as well as controlling the genetic characteristics of the colony, leading to more reliable experimental results. 

Returning to breeding mice following the COVID-19 lockdown presents many challenges but also an opportunity to apply best practices to colony management. In response, we have convened an expert working group to generate best practice guidance for breeding and colony management, in light of the scenarios facing research and technical staff re-starting breeding and experiments following interruption due to lockdown. 

The working group includes experts in breeding, archiving, colony management and experimental design from academic and commercial organisations. The group has combined their knowledge of colony management and experimental design to define current best practices in key areas, including best practice for archiving strains, breeding strategies to avoid genetic drift and using intermittent breeding strategies as an alternative to constant mating to reduce animal use. These best practice concepts were then included in the development of strategies and advice for common scenarios when returning to breeding and research following a pause or interruption (e.g. an experiment was only partially completed prior to lockdown and now animals are required to complete the remaining part of the experiment).  

The aim is that this guidance will support researchers and technical staff involved in breeding mice to follow best practice in colony management, when returning to research and continuing into the future. 

Visit our breeding and colony management resource for more information.

Working group members

Name Affiliation

Prof Ian Jackson (Chair) 

MRC Human Genetics Unit, University of Edinburgh 

Dr Simon Bate 


Mr James Bussell 

University of Oxford 

Ms Caroline Chadwick 

University of Birmingham 

Mr Brendan Doe 

CRUK Cambridge Institute 

Dr Ellen Forty 

The NC3Rs 

Ms Sarah Hart-Johnson 

Francis Crick Institute 

Prof Monica Justice 

The Centre for Phenogenomics/ University of Toronto 

Dr Natalia Moncaut 

CRUK Manchester Institute  

Dr Peter Oliver 

MRC Harwell 

Dr Esther Pearl  

The NC3Rs 

Dr Michelle Stewart 

Mary Lyon Centre (MRC Harwell) 

Dr Sara Wells 

Mary Lyon Centre (MRC Harwell) 

Dr Jacqui White 

The Jackson Laboratory