Effects of dietary vegetable oils on liver and gonad fatty acid metabolism and gonad maturation in gilthead seabream (Sparus aurata) males and females

Abstract

A 20-week growth trial was conducted to investigate the effect of two dietary blended vegetable oils (VO) on liver lipogenic enzyme activity, liver and gonad lipid class composition and fatty acid profiles, serum sex hormones, and gonad morphohistology in gilthead seabream, Sparus aurata. Three groups of fish (BW i 130.9 ± 3.1 g) were fed, close to satiation, three experimental diets: a control (CTRL) contained fish oil (FO) as the sole lipid source (100% FO) and two VO-blended diets in each 60% of FO was substituted by an equal mixture of cottonseed oil (CO), sunflower oil (SFO) and either linseed oil (LO) or soybean oil (SBO), designated as LO or SBO diet, respectively. Each diet was assigned to triplicate groups of fish. Results showed that all dietary treatments presented no significant (P [ 0.05) differences in growth rate and feed conversion ratio for sexes combined. Enzyme activities of liver lipogenic enzymes of LO-fed fish (glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME) and fatty acid synthetase (FAS)) were not statistically (P [ 0.05) different from those of CTRL fish. Only in the group of fish fed the SBO diet, G6PDH was slightly higher (P \ 0.05) for both sexes, while ME showed a significant (P \ 0.05) higher activity only in females relative to CTRL fish. Liver FAS enzyme activity remained unaltered among dietary groups. VO-fed fish recorded a significant (P \ 0.05) increase in total lipid (TL) and triglyceride (TAG) contents in both liver and gonad, more pronounced in females than in males, concurrent with a significant (P \ 0.05) decrease in cholesterol (CHL) and phospholipids (PL), more obvious for the SBO-fed fish, as compared to CTRL. The fatty acid (FA) composition of liver or gonad reflected that of the supplied diet and evidenced a significant (P \ 0.01 or \0.05) alteration in the majority of individual FA in VO-fed fish compared to CTRL. There were decreased levels of ARA (20:4 n-6), EPA (20:5 n-3), and DHA (22:6 n-3) in VO-fed fish, more pronounced in females than in males, compared to CTRL. The liver and gonad FA profiles, for males and females, reflected the composition of the diet and showed sex variation in the output of multivariate principal component analysis (PCA). Feeding fish VO diets has also led to a significant (P \ 0.05) reduction in serum estradiol level by 15.8 or 22.3% in LO-or SBO-fed fish, respectively, and in testosterone level by 7.7% in the latter dietary group only compared to the CTRL. Histomorphological examination of ovary and testis has indicated a relative retardation in oogenesis and spermatogenesis in VO-fed fish, less obvious in the LO-fed fish compared to CTRL. These results suggest a preference of LO over SBO blend diet in terms of liver lipogenic enzyme activity, liver and gonad lipid content, lipid class composition and fatty acid profile, serum sex hormones as well as gonad maturation. PCA analysis of gonads highlighted the importance of using a 100% marine FO diet for gilthead seabream broodstock for the recovery of a normal FA profile in g...

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.…”

“…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).…”

Biometric and metabolic profiles associated to different rearing conditions in offshore farmed gilthead sea bream (Sparus aurata L.)

“…In these conditions, TAG accumulation was previously found to be associated with an overall reduction of essential fatty acids, especially n‐3 DHA in gilthead fillet, which goes to the detriment of nutritional quality of the commercial product. Additionally, it is worth remembering that DHA, more than EPA, is selectively retained in gonads during the prespawning period, which further confirms the previously observed progressive depletion of DHA from muscle during growth . Nevertheless, stored TAGs were found to be rich in n‐3 fatty acids , and this may explain the discriminant upward signal associated to n‐3 FA found in STOCSY plot (Fig.…”

Dietary oils influence ovary and carcass composition and embryonic development of zebrafish

“…Lower levels of E2 were found in Sparus aurata on a vegetable oil diet (cotton seed oil, soy bean oil and linseed oil) compared with fish on a fish oil‐based diet (Wassef et al . ). Furthermore, Kassem et al .…”