Vegetable oil blend as alternative lipid resources in diets for gilthead seabream, Sparus aurata

Abstract

The recent decreasing worldwide supplies of marine oils have forced the aquaculture industry to investigate alternative lipid sources for use in marine fish feeds. The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on gilthead seabream (Sparus aurata) growth performance, nutritive utilization, body composition, and fatty acid profile as well as feed cost. Two dietary vegetable oil (VO) mix blends (VO1 and VO2) in which: sunflower (SO), cottonseed (CO) and linseed (LO) for VO1 or soybean oil (SBO) for VO2, were tested as 60% fish oil (FO) substitutes versus the 100% FO control or reference diet (FO). Three iso-proteic (46% CP) and iso-lipidic (18%) experimental diets were hand fed, twice a day, 6 days a week to apparent visual satiety to triplicate groups of seabream growers (average initial weight, 130.9 ± 3.44 g), until fish reached market size (300-400 g/fish) after 20 weeks at mean ambient temperature 27.0 ± 1.8°C. All experimental diets were well accepted by seabream growers regardless of the different lipid sources used, as overall mean feed intake (FI) and daily intake (DFI) were not significantly different (P [ 0.05) among dietary treatments. In terms of growth performance, fish fed VO1 diet (with LO) exhibited a relatively lower, but significant (P \ 0.05), total weight gain (WG) than fish fed all FO diet (FO). However, mean value of WG of fish fed either vegetable oil-tested diet was nonsignificantly different. Feeding seabream growers vegetable oil (VO) diets (VO1 or VO2) had no significant effect on specific growth rate (SGR), daily weight index (DWI), or feed conversion ratio (FCR) among dietary treatments. Consumption of VO for 20 weeks did not significantly alter the major nutrient composition of fish, but the muscle fatty acid (FA) profile was significantly altered compared to the reference FO diet. Comparatively reduced levels of eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA), as well as elevated levels of linoleic and linolenic acids (LA and LNA) compared with fish fed the FO were noticed. In terms of economics, 17 or 20% reduction in Kg feed cost was obtained for diets VO1 or VO2, respectively. In terms of growth performance and cost, VO2 diet showed slight relative superiority over VO1 diet. However, in terms of liver structure morphology, VO1 diet (with LO) has resulted in less fat-infiltration and altered hepatic cells than VO2 (with SBO). As these traits do not affect yield or the price paid for the fish, VO2 diet has therefore been considered better than VO1 as complementary lipid sources for gilthead seabream grower diets.

Comparative evaluation of sunflower oil and linseed oil as dietary ingredient for gilthead seabream (Sparus aurata) fingerlings

“…Furthermore, the increase in the levels of DHA from fish fed diets with low dietary levels of this fatty acid has led to speculate that DHA was selectively retained in fish muscles compared to other fatty acids. Similar observations were also reported for bigger sizes of the species (∼130 g/fish) fed a vegetable oils blend for 20 weeks (Wassef et al, 2009(Wassef et al, , 2012 and for European seabass (Dicentrarchus labrax) as well (Mourente et al, 2005). In the present study, the relatively less DHA deposition in the muscle with LO70 diet than with SFO70 diet (Tab.…”

“…However, in terms of cost, a combination of 32 g FO plus 48 g LO or SFO kg −1 diet can be also used with the least consequences on growth, feed utilization and nutrient retention efficiency. This notion is higher than the maximum level of FO-substitution by soybean oil (47%) in gilthead seabream juveniles diet (Kalogeropoulos et al, 1992) and closely resemble to that for cottonseed oil (Wassef et al, 2014) or a blend of soybeen, linseed and cottonseed oils (Wassef et al, 2007(Wassef et al, , 2009). …”

“…Prior studies have examined the use of LO in gilthead seabream diets, as a partial substitute of fish oil, had reported different inclusion levels associated with the use of both dietary protein and lipid sources. In fishmeal-based diets, 50% and 60% FO-substitution by LO either singly (46% CP and 25% L) or in a blend (46% CP and 18% L) can produce similar results to diets containing 100% fish oil during the grow-out phase of this species (El-Kerdawy and Salama, 1997;Izquierdo et al, 2003;Wassef et al, 2009). In addition, within a plant protein-rich diets higher ratio of added-fish oil (66%) was substituted by a mixture of vegetable oils, contained LO, without compromising growth performance or feed efficiency of fish (Benedito-Palos et al, 2008).…”

“…A control, 100% FO diet (CTRL) was firstly prepared and then 6 additional diets were prepared by replacement of 50, 60 or 70% of added-FO by either linseed oil (LO) or sunflower oil (SFO) singly in diets designated as LO50 or SFO50, LO60 or SFO60 and LO70 or SFO70 respectively. All diets were produced in the laboratory as extruded pellets as described earlier in details by Wassef et al (2009), stored at −20 • C before being used. Fish were hand fed as two meals per day, six days a week close to apparent satiety, and daily feed intake was recorded.…”

“…Previous studies on nutrition of this species have highlighted the importance of fish oil as a major constituent in their feeds. However, continuous efforts have been directed towards evaluation of different vegetable oils, either singly or in combination, as FO-substitutes for the species (Alexis, 1997;Benedito-Palos et al, 2008, 2009, 2011Diaz-Lopéz et al, 2009;El Kerdawy and Salama, 1997;Izquierdo et al, 2003;Menoyo et al, 2004;Wassef et al, 2007Wassef et al, , 2009Wassef et al, , 2012Wassef et al, , 2014. The most commonly investigated vegetable oils, in these earlier research, were: soybean oil (SBO), linseed oil (LO), rapeseed oil (RO), and to a lesser extent palm oil (PO) and olive oil (OO).…”