Abstract
Marine by-products can compose up to 70% of the total weight of products from fisheries, most of which are discarded. However, these by-products are rich in highly unsaturated fatty acids that are not synthetized by most marine animals produced by aquaculture. Here, we used three marine by-products (shrimp head, Catarina scallop viscera, and Pen shell viscera) to produce lipid-rich (72.9–144.6 g/kg) meals which were used to partially substitute commercial fishmeal (FM) on feeds that were used to grow Almaco Jack (Seriola rivoliana) juveniles for 10 weeks. The content of 20:5n-3 and 22:6n-3 in tissues of fish fed shrimp and Pen shell presented values similar to controls, but the former had a better effect on growth, lipid, and phytosterols levels. Catarina meal had lower concentration of 20:4n-6 and 22:6n-3 in feed but promoted higher proportion of 20:4n-6 in muscle and 22:6n-3 in liver, indicating a selective conservation in relation to other fatty acids. Catarina meal contained traces of 18:5n-3 (0.02 g/kg) indicating that scallops probably ingested dinoflagellates; after testing, phycotoxins like okadaic acid (OA) and dinophysistoxin 1 (DTX1) were detected by mouse bioassay, by lateral flow immunochromatography, and quantified by HPLC–MS/MS. The presence of these toxins at the detected concentrations (OA: 27.64 µg/g and DTX1: 10.31 µg/g) affected almaco jack juveniles, a setback that needs to be addressed before meal manufacturing from mollusks. Marine by-products rich in lipids can be used to reduce the use of FM in the diet, and their use improve the lipid content and growth compared to control diet with FM.Graphical Abstract
Highlights
Fishmeal (FM) has been traditionally used as the main source of protein in fish aquaculture, but the steady decline in global fisheries and the higher demand for animal feed have drastically limited the availability of FM and has increased its cost [1]
We found EPA + Docosahexaenoic acid (DHA) in the feed ranged from 12.4 to 14.5 g/kg of the diet for reference diet (RD), shrimp head diet (SD), and Pen shell diet (PD), but were below 10 g/kg for Catarina diet (CD) and SCPD, so even these diets had sufficient highly unsaturated fatty acids (HUFA) n-3 according to literature
We supposed that Catarina scallop viscera meal could have been contaminated: Here, we found that Catarina scallop viscera meal did have low but detectable levels of 18:5n-3 (0.02 g/kg)
Summary
Fishmeal (FM) has been traditionally used as the main source of protein in fish aquaculture, but the steady decline in global fisheries and the higher demand for animal feed have drastically limited the availability of FM and has increased its cost [1]. While partial or total marine by-products substitution of FM has begun to be evaluated with mostly good results on growth and survival in diets for shrimp [5, 6] and marine finfish [2, 7, 8, 9], there are still several concerns that remain, mainly the quantity of by-product meal from individual sources that can be produced each year and be commercially available for inclusion in feeds, an adequate ratio of n-3 and n-6 HUFA, enough docosahexaenoic acid (22:6n-3, DHA), the presence of antinutrients, toxins, hormones, phytosterols or other nutrients in byproducts that can be or not present in FM and that can affect survival and growth in organisms fed feeds made with these by-products. We aimed at evaluating the lipid composition in muscle, liver, brain, and mesenteric fat of Seriola rivoliana juveniles fed diets containing Pen shell viscera, Catarina scallop viscera, and/or shrimp heads lipid-rich meals to assess the use of marine by-products as partial substitutes for fishmeal in feeds
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