Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 21/09/2023 16:00:0021/09/2023 16:15:00Europe/ViennaAquaculture Europe 2023PROTEIN VALUE AND AMINO ACID DIGESTIBILTY OF VARIOUS RAW MATERIALS FOR FISH DIETS AS EVALUATED SEPARATELY IN TWO IN VITRO AND TWO IN VIVO MODEL SYSTEMSStolz 2The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


 T. M. Kortner1*, A. Rieder2, K. Præsteng1, E. Hage1 , Å Krogdahl1 , D. Peggs3, R. Fontanillas3 , M. A. Chacon4, A. Bitan4 ,  F. Gandolfi5 , G. Løkka1


1 Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of  Life Sciences, Ås, Norway

2Nofima , Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway

3 Skretting Aquaculture Innovation, Stavanger, Norway

4National Center for Mariculture, Israel Limnological & Oceanographic Research Institute, Eilat, Israel

5Department of Agricultural and Environmental Sciences, University of Milan, Italy

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 Variation  in  nutrient digestibility is among the most critical points of variation in feed quality  and constitutes  a key parameter when evaluating  new  feed raw materials for fish.  Nutrient digestibility is  traditionally assessed in vivo by animal feeding trial s, but  recent EU obligations to put the 3Rs  concept into practice have facilitated  research  initiatives  to develop  complementary in vitro methods.  One of the current project initiatives addressing this topic is the H2020-FETOPEN project Fish-AI, which aims to develop an in vitro  screening platform based on rainbow trout (Oncorhynchus mykiss) digestive enzymes and intestinal cells to  evaluate  nutritional and health  values  of novel aquafeeds . As part of this project, we have developed a static in vitro digestion (IVD) model for simulating the in vivo feed digestion in rainbow trout. In the present study ,  the  performance of the Fish-AI IVD model was assessed  by  comparisons with two independent in vivo feeding trials using juvenile rainbow trout and mink (Neovison vison ) as experimental animals.  In addition, the Fish-AI model was compared against the standardised  human in vitro model INFOGEST1.

Materials and methods

 A total of seven diets  based on commercially relevant protein raw materials with assumed contrasting effects on  protein  digestibility were formulated. Six test feeds contained the challenging raw materials guar meal and  soybean meal  at  relatively  high inclusion levels, feather meal at low and high inclusions, and the combinations guar/feather and soybean/feather. A  diet  high  in  fish meal  was included  as a reference. The study in rainbow trout  comprised  a 5-week  feeding trial  using fish with an average  start weight of 55 grams. Fish were fed the seven experimental feeds in duplicate tanks each. Fecal collection  was conducted by stripping. The mink trial was carried out using adult male mink with a m ean body weight of 2.8 kg .  Four healthy mink were assigned for each of the seven experimental diets. The animals were kept in individual cages equipped for controlled feeding and quantitative faecal collection. The experiment lasted for 14 days . F eed and faeces  samples were analyzed by established procedures2.  The  Fish-AI IVD procedure was based on the static INFOGEST model  with several modifications, including the use of  enzyme  extracts and bile obtained from rainbow trout , whereas the INFOGEST protocol was performed as described elsewhere1.  The IVD products  from both in vitro  procedures were analyzed using size exclusion chromatography (SEC)  and  quantification of soluble n itrogen with Dumas for estimation of the proportion of small  soluble peptides potentially available for uptake3. Difference among diet groups  was analyzed for statistical significance using a one-way ANOVA followed by Fischer’s LSD test. The level of significance was set to p<0.05.

Results and discussion

 Figure 1 illustrates the results regarding apparent  protein  digestibility for  the seven experimental diets as tested in the four separate model systems. Significant effects of diet were evident. Rainbow trout fed either the control, guar-high, or soya-high diet generally showed high (>95%) protein digestibilities, whereas inclusion of feather meal in the diet, singly or in combination with guar or soya, clearly reduced protein digestibility.  The results obtained with mink were in overall accordance with the results obtained from the study in rainbow trout and strengthen the observation that the biological value of the feather meal protein was low.  The  results from the two in vitro model systems  displayed relatively  similar  protein digestibility profiles among the experimental diets as the  two in vivo models, thus  demonstrating that the low protein  value of the diets containing feather meal also could be detected in vitro . The absolute values of protein digestibility were higher for the INFOGEST than for the Fish-AI IVD procedure (70-86 vs. 43-62%) and indicate that there is still room for improving the Fish-AI IVD efficiency. These studies are currently ongoing and will be presented and discussed.


This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 828835.