Incorporating a soybean meal-based diet in a mixed feeding schedule leads to comparable growth performance in zebrafish (Danio rerio) while reducing fishmeal usage

The primary operational expense in fish farming is the cost of feed. While fishmeal (FM) is recognized as a high-quality protein ingredient for use in aquaculture feeds, it is also reliant on finite marine resources leading to economic and sustainability concerns. Soybean meal (SBM) is a widely available and cost-effective protein alternative, but high dietary inclusions or repetitive use can lead to detrimental effects on growth performance and intestinal health. Mixed feedings schedules utilizing diets with varying nutritional composition or ingredient sources have been shown to be successful in reducing feed costs while maintaining growth performance metrics. Due to the beneficial effects of FM, we hypothesize that utilizing a pattern of alternating FM- and SBM-based diets may promote overall feeding efficiency while reducing the environmental and economic load of FM usage. Thus, this study employed zebrafish as a model to investigate the effects of incorporating a high inclusion (55.7%) SBM-based diet in a mixed feeding schedule. Specifically, the objective of this study was to evaluate an alternating feeding approach using FM- and SBM-based diets on growth performance, feed intake and feed utilization, and intestinal health in juvenile zebrafish. Four dietary treatments were evaluated in experimental triplicate: continuous FM, continuous SBM, daily alteration of FM and SBM, and weekly alteration of FM and SBM. Treatment tanks were stocked with 21 juvenile zebrafish per tank and fish were fed to apparent satiation with respective diets for four weeks. This study found no significant effect of feeding schedule on survival, final weight, feed conversion ratio, or markers of intestinal health. However, the alternating groups utilized significantly less FM at 45-58% of the FM used in the FM only group (p < 0.0001) leading to cost savings averaging 22-29% (p < 0.0001). While not statistically significant, the weekly alternating group resulted in the numerically highest final weight with comparable feed utilization metrics to the FM only group. This study provides preliminary evidence for the success of mixed feeding schedules utilizing plant proteins while minimizing the negative effects attributed to SBM utilization.