Effect of Dietary Protein Source and Quantity on the Growth and Body Composition of Juvenile Danio rerio
Authors: Williams Michael Britt , Dennis Lacey , Miyasaki Nathan , Barry Robert , Powell Mickie , Watts Stephen , Smith Daniel 
Published: November 2023

The zebrafish Danio rerio is increasingly utilized as a laboratory model of human disease, including morbidities associated with undesirable body composition. Nutritional status of study animals, such as zebrafish, has been shown to impact study results. A standardized, open‐source diet is not currently utilized, leading most labs to rely on commercial diets that may supply differing or inadequate nutrition. Studies with nutritional manipulation suggest early life exposure (types and amounts of nutrients) can have life‐long (or at least late‐life) effects on health and well‐being (e.g. calorie restriction at early life only, crowded litter effects, etc.). Protein, as a macronutrient, has the largest direct impact on growth outcomes as it is used for the synthesis of structural and functional components related to lean mass.To better understand how dietary protein source and quantity impacts growth and body composition, we raised 28 day post fertilization D. rerio on 12 different dietary treatments (2 cohorts of 3 tanks per cohort, n~ 10 fish per tank) for 12 weeks. Diets contained 4 protein sources (fish protein hydrolysate, soy protein isolate, casein, or a mixture of all three sources and including wheat gluten) added to make 3 final protein diet levels (18, 33, or 48 percent dry matter of the diet) and were provided at a rate consumed within 30 minutes when fed twice daily (at 900 and 1800 hr). Following 12 weeks, fish from each diet treatment were measured for weight, length, and girth. For a subset (n~12) of fish, individuals were dried to constant weight and terminal body lipid was determined using chemical carcass analysis. Percent dry lipid in whole body was inversely proportional to dietary protein level in the males receiving casein, fish and soy protein sources, but only for females receiving fish and soy protein sources.Additionally, a separate cohort of fish were raised on 2 different diets at temperatures of 20°C and 30°C (2 tanks, n~ 25 fish per tank). Diets contained 2 protein sources (soy protein isolate or mixed protein source described above) at 48 percent dry matter of the diet provided as in the first part of the study. This allows rearing temperature to be evaluated as an environmental variable that may impact body compositional changes and growth concomitantly with dietary protein source. These fish also were evaluated for terminal weight, length, girth, and total body lipid content. Percent dry lipid in the whole body was lower at increased rearing temperature in both males and females, indicating a direct environmental effect on body composition. For females dry percent lipid was significantly less in fish receiving the mixed protein source compared to the soy protein source at both 20°C and 30°C, suggesting an interaction between environment and protein quality. In males the same outcome was seen, but only in fish reared at 20°C and not in the 30°C treatments.These data suggest an important role of dietary protein source and quantity, and the temperature of the physical environment, on growth and body composition outcomes. We hypothesize these differences are based on changes in nutrient partitioning and expenditure.Support or Funding InformationResearch and animal care supported in part by the American College of Laboratory Medicine and the Aquatic Animals Research Core within the UAB NORC (P30DK056336).