Manipulating feeding rate and protein quality may improve growth and feeding efficiency of culture species. Feeding to satiation may yield high growth but low feeding efficiency while feeding restrictively may produce similar growth and higher feeding efficiency. Regarding protein quality, fishmeal is considered high-quality protein while less expensive plant-based proteins (e.g. soybean) are considered lower quality as they may not offer complete amino acid profiles and contain anti-nutritional factors that negatively affect growth performance, survival, and gut health. However, whether feeding rate, protein quality, or their interaction has a greater effect on growth and feeding efficiency responses variables in Zebrafish is unknown.
To determine whether feeding rate and protein quality individually or interactively affect growth and feeding efficiency, juvenile Zebrafish (Danio rerio) were offered either fishmeal- or soybean meal-based diets restrictively or to satiation. Weight per fish, feed intake, and feed conversion ratio (FCR) were measured at 30, 37, and 44 days post hatch and analyzed using repeated measures ANOVA.
Zebrafish fed to satiation had higher body weight and percent weight gain than those fed restrictively. Protein quality and feeding rate individually and interactively affected feeding efficiency metrics: Zebrafish fed soybean-based diet to satiation presented higher feed intake and FCR than individuals in all other treatment groups. The lower feeding efficiency but higher growth of Zebrafish fed soybean-based diet to satiation likely indicates impaired nutrient absorption as individuals consumed a greater amount of feed but grew comparably to those fed fishmeal-based diet to satiation. The observed differences in measured response variables between protein qualities and feeding rates highlight the importance of determining interactive effects in nutritional studies, as well as the use of the right feeding approaches.