First attempt at using a synthetic diet in short-lived killifish, a vertebrate model of ageing.

Diet standardization of model organisms is crucial for experimental consistency and repeatability in laboratory research, yet laboratory fish often lack species-specific, open-formula standardized diets. This study aims to address this gap by testing the effect of macronutrient content on the performance of Nothobranchius furzeri, an intensively studied research model in biogerontology, and providing the basal formula of the purified diet for further development to support the good and consistent performance of this species in laboratory research. After 5 months of feeding, growth, body condition, reproduction and feed efficiency were compared among treatments of individually housed fish fed by one of the two purified diets, (1) high protein (~66% protein, 9% lipid) and (2) low protein (34% protein, 22% lipid), and control bloodworm-fed fish. Survival on both purified diets and male growth on the high-protein diet were comparable to that of the control. The absolute protein intake regulated fish growth irrespective of the total caloric intake. Only the low-protein diet with 22% lipids supported a comparable fertilization rate to the control group. Female performance exhibited greater diet dependency than that of males. This suggests that a female-specific formula should be developed in the future, as males would perform well on a wider variety of diets. This study provides the first data on the performance of N. furzeri fed with a purified diet and establishes a baseline diet formula for further refinement of a standardized laboratory diet for N. furzeri.