Shrimp research has recently focused on the development of practical feeds that use plant proteins as substitutes for animal protein sources (Amaya et. al., 2007; Sabry-Neto et al. 2017; Guo et. al., 2019). According to Davis et al. (2004) and personal communication with shrimp industry partners (Euroshrimp: The Shrimp Network), the use of a purely plant protein feed may be limited by a variety of factors. These include amino acid profile, lower mineral content, low/limiting poly-unsaturated fatty acid content, the presence of antinutritional factors and lower palatability (Amaya et al., 2007). Feed attractants are being considered as a means of improving diet palatability and intake of feed in Browdy et al., 2006). The efficacy of krill meal as attractant has been already proven in shrimp diets however, much research is needed for alternatives and sustainabily produced attractants. In this study, we investigated the potential of meal from gammarids and polychaetes, low trophic organisms and can be bred from agricultutal by-products and processing residues, as attractants in plant-based diets for white leg shrimp (Malzahn, A.M. et al., 2023; Ribes-Navarro et al., 2022). A controlled feeding experiment was conducted to evaluate the effects of the inclusion of the gammarids, Gammarus locusta, Gammarus pulex the polychaete Nereis virens, and Krill Euphausia superba as attractants in white leg shrimp diet. Growth performance, feed intake, survival rate, health and immune responses were evaluated.
Material and Methods
A one-month controlled feeding experiment with Whiteleg shrimp (L. vannamei) was conducted with 40 shrimps per tank in quadruplicate. Shrimp with an initial weight of 0.39 ± 0.02 gr were hand-fed four times daily according to the recommended feed rate, expressed as percent of body weight per day (Wyk et al., 1999) in a recirculation aquaculture system (RAS).
Six experimental diets were formulated: a commercial feed (FMD) as positive control with 10-20 % fishmeal content; a negative control (PD) containing no ingredients from marine sources and consisting of 100 % vegetable proteins and no added attractant. In addition, four test diets were produced from PD and with the addition of the 2% attractant (krill meal, gammarid meal (G. locusta and G. pulex) and polychaete meal (N. virens)).
Growth performance, survival rate, feed intake were monitored. At the end of the experiment haemolymph and hepatopancreas samples were taken to determine metabolic parameters (glucose, acylglycerides and total heamolymph protein), immunological capacity (phenoloxidase activity), stress resistance (antioxidant capacity) and nutritional value (fatty acid profile).
Results and Discussion
Preliminary results showed that shrimp fed the N. virens diet showed significantly higher weight gain than both gammarid diets. No significant differences were observed between the other diets. Moreover, survival rate did not significantly differ between treatments (Figure. 1). To date, no conclusions are possible since the full data set is not yet available.
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Guo J., Huang Y., Salze G., Roy L. A. Davis D. A., (2019). Use of plant‐based protein concentrates as replacement for fishmeal in practical diets for the Pacific white shrimp (Litopenaeus vannamei) reared under high stocking density and low salinity conditions. Aquaculture nutrition 26: 225–232.
Shabry-Neto H., Lemos D., Raggi T., Nunes A.J.P., (2017). Effects of soy protein ratio, lipid content and minimum level of krill meal in plant-based diets over the growth and digestibility of the white shrimp, Litopenaeus vannamei. Aquaculture nutrition 23; 293-303.
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Ribes-Navarro, A., Alberts-Hubatsch, H., Monroig, Ó., Hontoria, F., Navarro, J.C., (2022). Effects of diet and temperature on the fatty acid composition of the gammarid Gammarus locusta fed alternative terrestrial feeds. Frontiers in Marine Science. 9.
Wyk P. V., Davis-Hodgkins M., Laramore R., Main K.L., Mountain J., Scarpa J., (1999). Farming Marine Shrimp in Recirculating Freshwater Systems. Harbor Branch Oceanographic Institution. Florida Department of Agriculture and Consumer Services BOB CRAWFORD, COMMISSIONER Contract No. 4520.
This research was supported by the ERA-NET BlueBio COFUND Project SIDESTREAM [Gran ID 68], cofounded through national funds provided by the the Funding by the German Federal Ministry of Education and Research (BMBF), FKZ161B0950B.