Do Standard Laboratory Practices Lead to Obese Zebrafish Populations?

The value of the zebrafish model is well established and its widespread utility is without question in the study of early development, environmental science, and translational approaches to human disease onset and progression. Outcome variability due to the absence of nutritional standardization within and among laboratories remains, and can be magnified due to a minimal understanding of the potential role of nutrition. The community continues to use embryos and adults derived from stocks in which the nutritional history is not defined, thus, direct or indirect effects of nutrients on outcomes cannot be evaluated. In this study we compared the growth demographics and body composition associated with feeding common commercial diets (closed formulation) and a purified reference diet to zebrafish. Twenty‐one day old juvenile fish were fed one of six diets (commonly used by the majority of laboratories in the US as determined by the Zebrafish Husbandry Association). Each diet treatment contained nine 2.8 L tanks, each containing 13 zebrafish (n=117 ind/treatment). Fish were fed twice daily (09:00 and 17:00 hr) at a ration of >5% body weight per day (based on the fastest growing treatment). Rations were adjusted biweekly. Weight gain varied among the diets, with 14 week mean weights varying among treatments from 670 to 950 mg fresh weight. Lipid content of males and females (ovary removed) ranged from 22 to 42 and 18 to 45% dry matter, respectively. As compared to fat content estimated in wild fish populations, the levels of body lipid reported here would suggest these lab‐reared zebrafish have excessive body fat that is relative to that observed in human obesity. These data support recent metabolic literature indicating zebrafish are excellent models for the study of obesity and related morbidities. Variations in growth and body composition analysis in response to common laboratory diets and practices highlight the problems associated with the lack of nutritional information and standardization of diets in the zebrafish research community. There is a critical need for the development of standardized diets and feed management strategies. This should be a high‐priority community effort among laboratories with support from ASN and NIH. The long‐term goal of nutrition research in zebrafish will be to identify the daily nutritional requirements and to develop appropriate standardized reference and open formulation diets for the zebrafish community. Support or Funding Information Research and animal care supported in part by the American College of Laboratory Medicine and the Aquatic Animals Research Core within the UAB NORC (P30DK056336).