Introduction
The global shrimp industry continues to grow revealing a farmed shrimp production of 6.0 Mt in 2018. Litopenaeus vannamei was the most produced species with 82.7% (FAO, 2020). Consequently, the requirement for formulated feeds globally increased to more than 8 million metric tons (van der Heide et al., 2018a). However, there is no study about using SM in shrimp diets. Therefore, the aim of the present study was to determine the suitability of using meal of Asterias rubens to partially replace FM in diets for L. vannamei.
Materials and methods
Sea stars A. rubens were harvested in the Kieler fjord (Germany) and their nutritional profile was evaluated before formulating the diets. Shrimps were fed with four different diets including 0%, 5.4% (20% FM replacement), 13.5% (50% FM replacement) and 21.6% (80% FM replacement) SM for 42 days in a recirculating aquaculture system (Table I). All diets contained the same basal ingredients and were formulated according to an isonitrogenous and isocaloric content. Survival, growth performance and feed intake of P. vannamei were determined at the end of experiment. Additionally, haemolymph samples were taken to evaluate the health condition measuring metabolic parameters (glucose, total protein, triglycerides), number of haemolymph cells and the phenoloxidase activity.
Results
Sea stars showed an acceptable nutrient composition containing up to 44% crude protein and 9% crude fat. All experimental diets were accepted by the shrimps. Shrimps fed the 80% diet with highest SM content (21.6%) achieved even significantly higher growth performance (One-way anova, p<0.05) than shrimps fed the 0% diet or commercial control diet (Table II). Overall, growth of shrimps and feed intake were significantly higher in the formulated diet groups (0, 20, 50, 80%) compared to the performance of shrimps fed the commercial diet. Results of survival (Table II) and health performance, analyzed by the phenoloxydase acitivity, haemolymph cell counts, glucose, triglyceride and total protein levels in the haemolymph, showed no significant difference between shrimp groups fed the experimental diets.
Conclusion
Sea star biomass very efficiently replaces FM in diets for L. vannamei providing high-level protein and fat sources. In the current study, the inclusion of SM to a dietary level of 21.6% resulted in excellent growth and shrimp health. Future studies may test a 100% replacement of FM with SM. As the shrimp aquaculture industry continues to expand globally, sea star biomass joins a growing list of sustainable alternative protein and fat sources to replace FM. The authors encourage the application of this neglected marine biomass resource in aquafeeds.
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