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Effects on performance and product quality in Atlantic salmon fed diets reduced in organic pollutants

Jan Olli¹, Bente Ruyter², Turid Mørkøre^2, Harald Breivik³, Aimo Oikari⁵, Aleksei Krasnov², Olav Thorstad⁴, Åshild Krogdahl⁶ , Gunnar Berge⁸ and Torbjørn Åsgård^7*

¹ AVS Chile SA, Casilla 300, Puerto Varas, Chile

² The Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima), P.O. Box 5010, NO-1432 Ås, Norway

³Neperdo™ Biomarine, Porsgrunn, Norway

⁴ Pronova,BioPharma P.O Box 2109, NO-3202 Sandefjord, Norway

⁵University of Jyväskylä, , P.O.Box 35, FIN-40014 Jyväskylän yliopistoy

⁶Norwegian School of Veterinary Science, Oslo, Norway.

 ⁸Pronova,BioPharma P.O.Box 420, 1327 Lysaer, Norway.⁷ The Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima), NO-6600 Sunndalsøra, Norway

Oily fish, including Atlantic salmon, due to their content of omega-3 fatty acids, are considered healthy for human consumption. However, marine raw materials used in fish diets are considered a major source of persistent organic environmental pollutants (POPs). Advice regarding fish consumption has therefore been complicated by reports that some species are burdened with potentially harmful levels of POPs, such as dioxins, PCBs and brominated flame retardants (BFRs). Despite the rather low levels of environmental pollutants found in farmed Atlantic salmon, there is still some concern about the levels found. One should therefore aim at reducing the level of POPs in aquacultured fish, in order to strengthen the “healthy image” of the product. As a way to reduce these POPs in farmed fish, Pronova

BioPharma Norge AS has developed a short path distillation process using a volatile working fluid efficiently removing POPs from fish oils. Potential beneficial effects in the farmed fish from reducing the POPs in the feed oil, were tested in a study lasting from post smolt size to slaughter size at Gildeskål Research Station (GIFAS), Norway. The fish were given feeds containing purified or not purified fish oil, four replicates per treatment. The effects on growth, health and fillet quality were studied. There was a tendency for better growth and feed utilisation in the group receiving feed containing purified oil. This was particularly the case during periods of high growth when both the growth rate and feed utilisation rate were significantly better for the fish that received the feed containing purified oil. The salmon that received the feed containing purified oil appeared to better tackle the handling stress during the slaughtering process, measured as a delayed pH reduction after killing. Other stress markers showed the same tendencies. All the fish in the trial maintained a good red colour and firmness, but there was a tendency that fish that received the feed containing purified oil had a firmer texture. The difference in texture was most pronounced after freezing. The proportion of salmon with soft texture was then halved in comparison to the fish that received unpurified oil.

Improved P utilization of marine feed resources

Sissel Albrektsen, Kaspar Thorsen and Halvor Nygård

¹ Nofima, Kjerreidviken 16, N-5141 Fyllingsdalen, Norway

Sissel Albrektsen, Kaspar Thorsen and Halvor Nygård

Phosphorus (P) is an essential element for normal energy metabolism, skeletal development and growth in fish. The main natural source of P in commercial fish feeds are fish meals and fishery products. In fish bones, P is mainly present in a complicated crystal structure with Ca known as hydroxyapatite ((Ca- PO₄) OH₂) and as constituent of Ca₃(PO₄)₂ which must both be hydrolysed into simple phosphates for intestinal absorption. Fish have limited and variable ability to digest P from fish meal (~10 – 80 %), Cho and Bureau (2001), making it difficult to predict that adequate P is present for normal growth and health of fish. The low capacity for P digestion especially in salmonids releases about 60-80 % of dietary P through faecal and urinary excretion, which is a major environmental concern. In commercial fish farming, addition of soluble P salts in the diet is needed to avoid P deficiency. Expected limitations in rock phosphates in the near future and demand for this non-renewable resource as fertilizer element, has increased cost and the need for developing more P efficient low-pollution feed ingredients in diets for farmed fish.

Nofima Ingrediens has developed a process for alternative processing of the bone fraction of fish meal by separation and hydrolysis to make the minerals more water soluble and available. Improved digestibility (average 60%) has been demonstrated for macro minerals and trace minerals, although the variation in between elements appears to be high. Digestibility of P in fish meal produced from blue whiting has been increased by 70 – 80 % by separation and treatment of the bone fraction in strong acids. Alternative processed fish meals with improved P digestibility have further demonstrated improved growth and skeletal mineralization in salmon similar to that produced by addition of commercial soluble P salts. Selected results from a strategic institute program (NRC project 173499/130: Improved phosphorus (P) utilization of marine feed resources - Dietary impacts and optimal P nutrition in Atlantic salmon and Atlantic cod) related to technological processing of the bone fraction, and to biological performance of salmon fed the P improved feed ingredients, will be presented.

High growth rates in Atlantic salmon (Salmo salar L.) fed 7.5% fish meal in the diet. Micro-, ultra- and nano- filtration of stickwater and effects of different fractions and compounds on Atlantic salmon performance fed very low fish meal diets

Katerina Kousoulaki*¹, Hanne Jorun Olsen², Sissel Albrektsen¹, Eyolf Langmyhr¹, Paddy Campbell², Anders Aksnes^1
1 Nofima Ingredients AS, Kjerreidviken 16, N-5141 Fyllingsdalen, Norway
² BioMar AS

Stick water (SW) separated during fishmeal production from frozen herring was fractionated following successive micro- ultra- and nano- filtration steps. The press cake (PC) produced during separation of the SW and the different SW fractions were combined again to produce 4 fish meals containing different molecular size soluble protein mixes. The SW fractions used for the production of the experimental fish meals were 1) the micro-filtration (MF) retentate, 2) the ultra -filtration (UF) retentate, 3) the nano-filtration (NF) retentate and 4) the nano-filtration permeate. Four very high plant protein experimental diets were prepared using 1 of 4 experimental fish meals containing the different SW fractions. The experimental diets contained in total 75 g kg-1 fishmeal, of which 25 g kg-1 diet was superprime fish meal (SP) and 50 g kg-1 diet was 1 out of 4 experimental fish meals. The remaining dietary protein sources consisted of a mixture of commercial plant protein raw materials in equal amounts between the low fish meal experimental diets (soy protein concentrate 235 g kg-1 diet, corn gluten 235 g kg-1 diet; field beans 180 g kg-1 diet; wheat gluten 53.5 g kg-1 diet). A control diet was prepared containing 300 g kg-1 diet commercial fish meal. Three more very low fish meal experimental diets were prepared with 25 g kg-1 diet SP and 50 g kg-1 diet either PC alone or PC and crystalline taurine or crystalline hydroxyproline up to the level present in the high fishmeal control diet. The experimental diets including the SW fractions contained similar levels of water soluble protein (WSP) higher than the PC diets but lower than the control. All diets were iso-nitrogenous, iso-lipidic and iso-energetic and were fed to 8 triplicate groups of salmon (80 fish per group of initial body weight 133 g) for 69 days. High growth rates and low fish in-fish out ratios (FIFO) were achieved in salmon fed all the very low fish meal diets. Feed intake, fish body growth, whole body protein content, protein gain and morphometry were significantly affected by the inclusion of the different SW fractions in the low fish meal diets. We did not find any benefits for salmon performance by the supplementation of taurine or hydroxyproline alone to the low fish meal PC diets. The present work gives evidence on the multi-dimensional effects of the different marine water soluble components in fish performance. In order to identify novel high added value water soluble marine raw materials more studies must be conducted on the identification of specific functional effects of marine water soluble compounds in fish.