Fish meal may be partly replaced by a matrix of organic horse bean, pea and rape, and flax seed oil may replace fish oil in diets for organic rainbow trout without compromising growth performance and feed utilization

Dalsgaard, Johanne

Jokumsen, Alfred

Larsen, Bodil

Lund, Ivar

English

Organic Eprints

AbstractFish meal may be partly replaced by a matrix of organic horse bean, pea and rape, and flax seed oil may replace fish oil in diets for organic rainbow trout without compromising growth performance and feed utilization.Digestibility of dietary nutrients was measured directly using a modified, flow through Guelph System consisting of 18 tanks, and feeding each diet in triplicate (Figure 1).IntroductionThe production of rainbow trout according to organic certification regulations is increasing. To fulfill the demand of adequate feed there is a need to replace fish meal with organic, vegetable feed ingredients, as the principles of organic aquaculture encourage the development of feed that do not deplete global fish stocks. In addition, the organic code of practice does not allow addition of artificial amino acids to the feed, and optimization of the amino acid profile of organically based diets must therefore derive from the protein sources alone. The aim of this study was to evaluate the digestibility and growth performance of organic vegetable dietary ingredients as replacement for fish meal and fish oil in feed for organic rainbow trout (Oncorhynchus mykiss).Table 1. Composition of the experimental diets (%)Diet A B C D E FFish meal 59 51 43 35 59 59Fish oil 22 22 22 22 11 0Flax seed oil 0 0 0 0 11 22Horse bean 0 5 10 15 0 0Pea 0 5 10 16 0 0Rape 0 3 7 10 0 0Wheat 20 14 8 2 20 20ConclusionThe results indicate that fish meal may be reduced from 59 % to 35 % and replaced by a matrix of organic horse bean, pea and rape protein concentrates, and flax seed oil may replace fish oil by 100 % in feed for organic rainbow trout without compromising growth performance and feed utilization.National Institute of Aquatic ResourcesSection for AquacultureTechnical University of DenmarkXIV International Symposium on Fish Nutrition and FeedingQingdao, China. May 31 – June 4 2010 Organic vegetable proteins and oil in feed for organic rainbow trout (Oncorhynchus mykiss)Ivar Lund, Johanne Dalsgaard*, Bodil K. Larsen and Alfred JokumsenTechnical University of Denmark, DTU Aqua, Section for Aquaculture, The North Sea Research Centre, DK-9850 Hirtshals, Denmark. *E-mail: jtd@aqua.dtu.dkMaterials and methodsSix iso-energetic and iso-nitrogenous diets were prepared (Table 1 and 2), comprising a fish meal and fish oil based control diet (A) and three diets in which the inclusion of fish meal was gradually reduced from 59 to 35 % and replaced by a matrix of organic horse bean, pea and rape protein concentrates in the proportion of 1:1:0.7 (B, C, D). In the last two diets, the inclusion of fish oil was reduced by 50 and 100 %, respectively and replaced by flax seed oil high in omega-3 fatty acids (E, F).Growth performance was measured using a recirculation system consisting of 12 square formed fiber glass tanks and feeding each diet in duplicate for 9 weeks, from an initial weight of 60 g to a final weight of about 200 g (Figure 2).ResultsThe fish showed a relatively good growth performance with an average specific growth rate (SGR) of 1.8 % day-1, and an average feed conversion ratio (FCR) of 0.75, and there were no significant differences between the groups (Figure 3 and 5). In contrast, there were significant differences in the digestibility of protein, lipid and especially NFE in fish fed diets with organic protein concentrates (Figure 4). For fish fed diets with organic oils, the digestibility of oil was significantly higher in fish fed 100 % flax seed oil (Figure 6).Figure 1Figure 2AcknowledgementsThis work was supported by the International Centre for Research in Organic Food Systems (ICROFS).Figure 3 Figure 4Table 2. Proximate composition of the experimental diets (% dry weight)Diet A B C D E FProtein 46 47 46 47 45 46Oil 32 30 31 31 33 31NFE 13 14 14 14 13 14Phosphorus 2 2 1 1 2 2Energy (MJ/kg) 26 25 26 26 26 26Figure 6 Figure 5

Organic vegetable proteins and oil in feed for organic rainbow trout (Oncorhynchus mykiss)

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