Dietary Linseed Oil Reduces Growth While Differentially Impacting LC‐PUFA Synthesis and Accretion into Tissues in Eurasian Perch (Perca fluviatilis)

Abstract

The aim of this study was to evaluate the impact of replacing dietary fish oil (FO) with linseed oil (LO) on growth, fatty acid composition and regulation of lipid metabolism in Eurasian perch (Perca fluviatilis) juveniles. Fish (17.5 g initial body weight) were fed isoproteic and isoenergetic diets containing 116 g/kg of lipid for 10 weeks. Fish fed the LO diet displayed lower growth rates and lower levels of DHA in the liver and muscle than fish fed the FO diet, while mortality was not affected by dietary treatment. However, DHA content recorded in the liver and muscle of fish fed the LO diet remained relatively high, despite a weight gain of 134 % and a reduced dietary level of long-chain polyunsaturated fatty acids (LC-PUFA), suggesting endogenous LC-PUFA biosynthesis. This was supported by the higher amounts of pathway intermediates, including 18:4n-3, 20:3n-3, 20:4n-3, 18:3n-6 and 20:3n-6, recorded in the liver of fish fed the LO diet in comparison with those fed the FO diet. However, fads2 and elovl5 gene expression and FADS2 enzyme activity were comparable between the two groups. Similarly, the expression of genes involved in eicosanoid synthesis was not modulated by dietary LO. Thus, the present study demonstrated that in fish fed LO for 10 weeks, growth was reduced but DHA levels in tissues were largely maintained compared to fish fed FO, suggesting a physiologically relevant rate of endogenous LC-PUFA biosynthesis capacity.

Replacement of Marine Fish Oil with de novo Omega‐3 Oils from Transgenic Camelina sativa in Feeds for Gilthead Sea Bream (Sparus aurata L.)

“…This was clear in the PCA (NMDS Plot) analysis where all tissues, except brain, grouped according to the feeds, with ECO and DCO clustering in the same group. This indicated that the fatty acid composition of brain was more conserved and less affected by diet than the other tissues, consistent with other studies in the same species [20] and other teleost species [47, 48]. …”

Fish proteins not lipids are the major nutrients limiting the use of vegetable ingredients in catfish nutrition

“…The fatty acid composition in African catfish muscle is known to reflect dietary fatty acid composition (Ng et al., ). This positive correlation between dietary and muscle fatty acid compositions has also been widely reported in other fish species such as Atlantic salmon (Bell et al., ; Tocher et al., ), rainbow trout (Borquez, Serrano, Dantagnan, Carrasco, & Hernandez, ) and Eurasian perch (Geay et al., ). However, some fatty acids such as palmitic acid (16:0) can be selectively retained to be maintained at an optimal proportion in the phospholipid fraction.…”

“…Indeed, the relative elovl5 gene expression was stimulated in fish fed FMVO diet in comparison with the control FMFO diet. Previous studies also showed an increase in elovl5 gene expression and ELOVL5 enzymatic activity in fish fed olive, rapeseed, palm, linseed, perilla, soybean and ricebran oils compared to fish FO in rainbow trout (Buzzi et al., ), Atlantic salmon (Zheng, Tocher, et al., ; Zheng, Tortensen, et al., ), European sea bass (Geay et al., ), spotted scat, Scatophagus argus (Xie et al., ), Eurasian perch, (Geay et al., ) and Asian sea bass (Glencross et al., ). However, findings in the mentioned studies underlined also a stimulation of both fads2 gene expression and FADS2 enzymatic activity in fish fed VO‐based diets.…”

“…Indeed, FM constitutes the most suitable source of indispensable amino acids (IAA) for fish in covering their IAA requirements (FAO, 2010;Hertrampf & Piedad-Pascual, 2000;Manbrini & Kaushik, 1995). Regarding FO, its key role in fish nutrition is associated with its high levels of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) such as eicosapentaenoic acid (EPA, and docosahexaenoic acid (DHA,) and, to a lesser extent, n-6 LC-PUFAs such as arachidonic acid (ARA, (Buzzi, Henderson, & Sargent, 1996;Geay et al, 2010Geay et al, , 2015Henderson & Tocher, 1987). These LC-PUFAs are essential nutrients which play a pivotal role for fish growth, health and development.…”

“…The LC-PUFA biosynthesis pathway from C 18 precursors is composed of successive desaturation and elongation reactions catalysed by fatty acid desaturase (FADS) and elongation of very long-chain fatty acid (ELOVL). In European seabass, Dicentrarchus labrax (Geay et al, 2010), Atlantic cod, Gadus morhua (Hixson, Parrish, & Anderson, 2014) and Eurasian perch, Perca fluviatilis (Geay et al, 2015) fed a VO-based diet, it has been suggested that reduction in both growth performance and LC-PUFA levels in tissues could be attributed to limited LC-PUFAs endogenous synthesis. On the contrary, Nile tilapia, Oreochromis niloticus (Tocher, Bell, Mac Glaughlin, Mc Ghee, & Dick, 2001), Atlantic salmon, Salmo salar (Zheng, Tocher, Dickson, Bell, & Teale, 2005;Zheng, Tortensen, et al, 2005) and rainbow trout (Fonseca-Madrigal, Karalazos, Campbell, Bell, & Tocher, 2005) display relatively high capacities to grow while fed dietary vegetable oil.…”