Omega-3 (ω -3) are a demonstrated as an essential fatty acid (FA) family for human as their synthesis is either not possible for the a -linolenic acid (ALA, C18:3 ω 3) precursor or very weak starting from the precursor for the eicosapentaenoic acid (EPA, C20:5 ω 3) and docosahexaenoic acid (DHA, C22:6 ω3) long chain derivatives. They must therefore be supplied by foods
. Seafood products are the major source of ω-3 long chain derivatives in human diets
and shrimp L. vannamei may contribute to this intake. Shrimp flesh fatty acids (SFFA) composition is influenced by feed fatty acids (FFA) composition
. Omega-3 sources are rare and expensive, it is therefore essential to optimize their utilisation to produce sustainable and cost-effective feeds.
In this context, the present study aimed to screen the relative part of ALA and EP A among the total SFFA and their kinetics of assimilation regarding two different sources of dietary lipid: linseed oil (LO) and krill oil (KO) respectively. According to IAFFD, a reference database for raw materials composition , LO possesses 53.3%ALA and almost no EPA while KO includes 2.4%ALA and 17.4%EPA.
Materials & Methods
Two batches of experimental feeds were manufactured by coating 3% of the tested oils (LO or KO) on a control feed (37.3% crude protein and 7.8% fat).
135 juveniles of L. vannamei (0.1 g) were randomly distributed in 3 tanks (45 individuals/tank) resulting in a total biomass of 4.7± 0.1g per tank.
They were acclimatised in the tanks for 7 days with the control feed. A first sampling of 3 individuals per tank was performed at day 0 (9 shrimps ). Then, juveniles were fed with the experimental feeds: 1 tank with control+3%KO, one with control+3%LO and one with the control. The juveniles were fed at 5% of their estimated biomass per day. During the next 2 weeks, 4 samplings were made of 5 juveniles per tank for a total of 60 shrimp (20 shrimp per treatment). The SFFA composition was determined by Gas Chromatography with Mass Spectrophotometry (GC-MS) after extraction and saponification of the lipids of the abdomen.
Results and Discussion
The results showing the % of ALA and EPA as a function of time are presented in Fig.1 and Fig.2, respectively . The SFFA profile matches the FFA profile obtained with GC-MS and the FA oil’s profile described by the IAFFD database. These results suggest that coating is an efficient process to include specific FA in shrimp’s flesh.
Moreover, the relative part of ALA and EPA in shrimp flesh fed with control+3%LO and control+3%KO respectively increase by 1,8 % ALA for the juveniles fed with control+ 3%LO and by 2,5% EPA for the juveniles fed with control+3%KO between the 2 first samplings (T0 and T+3) . This result suggests that the kinetics of assimilation of ω -3 in shrimps flesh is quick.
Further experimentations with shorter sampling intervals are needed to precise these results.