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.