Nutrient Profile of Baltic Coastal Red Algae ( Delesseria sanguinea ), Baltic Blue Mussel ( Mytilus spp.) and King Ragworm ( Alitta virens ) as Potential Feed Material in the Diet of Rainbow Trout ( Oncorhynchus mykiss Walbaum, 1792): A Preliminary Assessment

Gregor Thum, Maria Grazia Cappai, Ralf Bochert, Hendrik Schubert and Petra Wolf
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Gregor Thum: Aquatic Ecology, Institute of Biosciences, University of Rostock, Justus von Liebig Weg, 18059 Rostock, Germany
Maria Grazia Cappai: Animal Nutrition, Department of Veterinary Medicine, Università degli Studi di Sassari, Via Vienna 2, 07100 Sassari, Italy
Ralf Bochert: State Research Centre of Agriculture and Fisheries, Institute of Fisheries, Susstrasse 8, 18375 Born, Germany
Hendrik Schubert: Aquatic Ecology, Institute of Biosciences, University of Rostock, Justus von Liebig Weg, 18059 Rostock, Germany
Petra Wolf: Institute for Nutrition Physiology and Animal Nutrition, University of Rostock, Justus von Liebig Weg, 18059 Rostock, Germany

Agriculture, 2022, vol. 12, issue 2, 1-8

Abstract: The use of selected Baltic coastal organisms as potential alternative feed material in the formulation of rainbow trout diets was studied. German coastal water organisms ( Delesseria sanguinea , seaweed red algae (A); Mytilus spp., Baltic blue mussel (M); Alitta virens, king ragworm (W)) were analyzed for nutrient, amino acid and mineral composition, and tested in comparative feeding trials. Five dietary treatments were supplied to a total of 165 juvenile rainbow trout (778 ± 111 g) for 75 days, allotted in 15 special brackish (3–5 practical salinity units (PSU)) water basins consisting of 11 fish each (3 fish tanks (300 L) at 12 °C per feeding group). The fish were fed as follows: C group, 100% basic diet (control); A group, 10% red algae in C diet; M group, 10% mussel in C diet; W group, 35% ragworm in C diet; AW group, 10% algae + 30% ragworm in C diet. Feed provision was performed manually, once a day, with the feed offer adjusted to 1.8% of fish weight for the respective tank. The fish weight gain (WG) and feed conversion ratio (FCR) were recorded. In the proximate analysis of the different coastal organisms, the lowest crude protein content in dry matter (DM) was found in blue mussels (10.9%), whereas it was almost doubled in algae (21.8%), with the highest being found in the ragworm (63.1%). By contrast, the crude ash content was the highest in the mussel (84.4%, mostly due to CaCO 3 from the shell), much less in the red algae (28.1%) and the lowest in the ragworms (20.1%). The gross energy (GE) concentration was the highest in the ragworm (18.8 MJ × kg −1 ), 12.1 MJ × kg −1 in the algae and the lowest in the blue mussel (2.93 MJ × kg −1 ). The final weight of the fish ranged between 1780 and 2310 g at the end of the feeding trial, being the lowest for the fish fed the diet combined with red algae (A diet group) and the highest for the fish fed the control diet. No differences in FCR were found for the fish fed the five dietary treatments ( p > 0.05), except for the W diet group (king ragworm has a lower FCR than that of the A group red algae, p < 0.05). The results from this trial suggest that at the tested amounts, both king ragworm and blue mussels are promising alternative feed material for rationing the rainbow trout diet, but not red algae, unless combined with ragworms.

Keywords: alternative protein source; amino acids; marine resources; rainbow trout (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
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