High levels of vegetable oils in plant protein-rich diets fed to gilthead sea bream (Sparus aurataL.): growth performance, muscle fatty acid profiles and histological alterations of target tissues

Abstract

The feasibility of fish oil (FO) replacement by vegetable oils (VO) was investigated in gilthead sea bream (Sparus aurata L.) in a growth trial conducted for the duration of 8 months. Four isolipidic and isoproteic diets rich in plant proteins were supplemented with L-lysine (0·55 %) and soya lecithin (1 %). Added oil was either FO (control) or a blend of VO, replacing 33 % (33VO diet), 66 % (66VO diet) and 100 % (VO diet) of FO. No detrimental effects on growth performance were found with the partial FO replacement, but feed intake and growth rates were reduced by about 10 % in fish fed the VO diet. The replacement strategy did not damage the intestinal epithelium, and massive accumulation of lipid droplets was not found within enterocytes. All fish showed fatty livers, but signs of lipoid liver disease were only found in fish fed the VO diet. Muscle fatty acid profiles of total lipids reflected the diet composition with a selective incorporation of unsaturated fatty acids in polar lipids. The robustness of the phospholipid fatty acid profile when essential fatty acid requirements were theoretically covered by the diet was evidenced by multivariate principal components analysis in fish fed control, 33VO and 66VO diets.

Molecular characterization and expression analysis of six peroxiredoxin paralogous genes in gilthead sea bream (Sparus aurata): Insights from fish exposed to dietary, pathogen and confinement stressors

“…Given the inhibitory role of PRDXs on immune response, these observations were consistent with a significant down-regulated expression of NKEFs. Also, the results of the present study evidenced a significant down-regulated expression of PRDX5 that agrees with a reduced risk of oxidative stress in fish fed vegetal oils due to the low levels of tissue polyunsaturated fatty acids [37,70]. However, at the same time, these animals exhibited a lower buffer antioxidant capacity to face stressful oxidative challenges and this paradoxical dualism might explain, at least in part, why dietary requirements for optimal growth do not necessarily coincide with those for optimal functioning of the immune and antioxidant system.…”

“…The chronic exposure to Enteromyxum leei, a commonly occurring intestinal parasite in gilthead sea bream [35], was chosen as infection model. The total replacement of fish oil with a blend of vegetable oils in plant protein-based diets was chosen as a model of nutrient deficiencies in essential fatty acids (EFA) with detrimental effects on growth [36,37] and antioxidant capacity [38]. High rearing density was also selected as a common aquaculture stressor to assess the stressmediated response in a pair-fed model [39].…”

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

“…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). On the other hand, more higher levels of dietary fish oil substitution up to 70% (equivalent to 56 g LO kg −1 diet) (Present study) or to 80% even in high energy diets (25% lipids) or to 100% in plant protein-rich diets (Benedito-Palos et al, 2008) had all resulted in a remarkably reduced growth rate, feed efficiency and inferior muscle major nutrients content than those fed only-fish oil diet.…”

“…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).…”

“…Both sunflower oil (SFO) and linseed oil (LO) are available worldwide as well as locally, and both are used widely in human food industry, but the latter is more expensive than the former. Despite, LO have already been studied, either singly or mixed, within highly energetic (25% L) fish meal (FM)-based diets (Izquierdo et al, 2003) or plant-protein rich diets (Benedito-Palos et al, 2008) for gilthead seabream, the high level of n-3 LNA makes this oil relatively unique in being able provide dietary n-3 PUFA at a potentially cost effective rate. On the other hand, reports on using sunflower oil (SFO) as a possible substantial partial substitute for dietary fish oil were mostly limited to Atlantic salmon, Salmo salar (Bell et al, 1993;Bransden et al, 2003;Menoyo et al, 2007;Torestensen et al, 2000), and European seabass, Dicentrarchus labrax (Yildiz and Sener, 2004).…”