Growth of rare minnows (Gobiocypris rarus) fed different amounts of dietary protein and lipids.

The rare minnow (Gobiocypris rarus) is a laboratory fish that is commonly used for toxicology research, but there is currently no standard lab diet for this model organism. Certain studies with rare minnows require specialized diets, so there is a need to better understand how manipulating nutrients affects the development and growth of this fish. We conducted two separate dose-response experiments to determine the effect of different levels of dietary protein or dietary lipids on the growth of juvenile rare minnows over 60 d. We measured growth rates and food intake over two periods of time: the first 20 or 30 d of diet consumption and the entire 60 d of each experiment. We found that different levels of dietary protein or dietary lipids produced significantly different growth rates during both the early phase and the entire duration of the study. Among experimental protein-variable diets, those with intermediate levels of dietary protein (around 35.2%) produced the highest growth rate. Among experimental lipid-variable diets, those with intermediate levels of dietary lipids (around 7.6%) produced the highest growth rate. Over all periods of both experiments, however, the control diet of bloodworms generally produced the highest growth rate that matched or exceeded that of any experimental diet. These results can guide investigators when using rare minnows in research, particularly when using custom and standardized diets.