Effects of fishmeal replacement, attractants, and taurine removal on juvenile and sub-adult Red Snapper (Lutjanus campechanus)

Four growth trials were conducted to evaluate the effects of fishmeal replacement with various levels of soybean meal (SBM) and poultry byproduct meal (PBM) on growth performance in practical diets for juvenile and sub-adult red snapper, Lutjanus campechanus. In addition, the need for taurine and palatability enhancement (krill meal) were evaluated in the high SBM, low fishmeal diet. Across the trials, ten diets were formulated to contain 36% protein and 10% lipids. All diets except for one included a taurine supplement of 1%. A supplement of 5% krill meal was added as an attractant to one of the low fishmeal and high SBM diets to explore potential palatability issues associated with plant-based proteins. No statistically significant differences were found between the performance of the basal diet and the PBM replacement diets, indicating that PBM is a suitable replacement for fishmeal in red snapper diets. On the contrary, a clear negative linear relationship was observed with increasing levels of SBM replacement. The reduced growth performance of high SBM inclusion diets is unlikely to be due to palatability issues, as no significant difference was observed between the performance of the high SBM diet with krill meal and an identical diet without krill meal. The significant reduction in growth observed in snapper fed a diet lacking a taurine supplement indicates that red snapper have a taurine requirement that is limiting at low (0.2%) levels. Gut samples were taken from fish that received the SBM diets to determine if reduced growth performance could be attributed to inflammation. However, no statistically significant difference was observed, indicating that reduced growth was not necessarily the result of a hypersensitivity reaction. Further investigation will be necessary to determine the optimal taurine requirement and required dietary supplements to improve the performance of low fishmeal feed formulations.

Automated summary

The study found that poultry byproduct meal can be a suitable replacement for fishmeal in red snapper diets, but high levels of soybean meal negatively affect growth performance, regardless of the addition of taurine or a palatability enhancer. Further investigation is needed to determine the optimal taurine requirement and dietary supplements to improve the performance of low fishmeal feed formulations.