Developing species-specific welfare scoresheets for the African Turquoise Killifish.

The African turquoise killifish Nothobranchius furzeri has emerged as a valuable vertebrate model for ageing research. Despite its increasing use in laboratory studies, systematic welfare monitoring approaches in N. furzeri is still emerging, and only a limited number of structured health-assessment frameworks have been proposed. Here, we present a welfare scoring system designed for daily monitoring of N. furzeri across its entire lifespan under laboratory conditions. Building on established zebrafish welfare frameworks and adapting them to the biological and ethological characteristics of N. furzeri, we identified a set of morphometric, behavioural and clinical parameters, including body condition score, external appearance, food intake, respiratory pattern, swimming activity, tank occupancy and clinical signs. Each parameter was assigned a numerical score ranging from 0 to 3, reflecting increasing degrees of welfare impairment. We further defined standardized intervention criteria, including humane endpoints, to support decision-making in cases of compromised welfare. Importantly, we established five distinct age stages to enable age-specific welfare assessment in two widely used wild-type strains, GRZ/GRZ-AD and MZM04-10. This scoring system provides a practical, reproducible, and easily implementable tool that can be seamlessly integrated into routine husbandry procedures. Its application is expected to promote standardized welfare assessment, improve experimental reproducibility, and enhance animal welfare standards in research using N. furzeri.