Navigating Uncertainties: How to Assess Welfare and Harm in Genetically Altered Animals Responsibly-A Practical Guideline.

The use of animals in research requires careful ethical consideration of whether the burden on the animals is justified. As one important part of the project evaluation, a harm-benefit analysis (HBA) must be carried out in order to approve projects in line with the EU Directive 2010/63/EU. This implies that harms and benefits must be assessed prospectively beforehand in order to weigh them. Although there are different methods of weighing, it is clear that an assessment of prospective harms and benefits is a precondition for any weighing procedure. In this context, projects that use genetically altered (GA) lines raise new issues. A unique challenge when using GA lines is the significant lack of knowledge in this context, making it difficult and sometimes impossible to estimate harm prospectively with sufficient certainty, since it is not predictable what sort of harm-if at all-the animals are going to experience. Therefore, this contribution aims to deal with the challenges of harm assessment in GA animals and their implications for welfare assessment and the HBA. A practical guideline is presented herein to serve as guidance for relevant harm factors and address the main challenges, particularly when dealing with uncertainties in the process of HBA.