The time course of fish oil wash-out follows a simple dilution model in gilthead sea bream (Sparus aurata L.) fed graded levels of vegetable oils

Abstract

The aim of the study was to determine whether changes in the tissue fatty acid (FA) profile follows a simple test dilution model after changing the dietary oil sources in gilthead sea bream. A 14-month trial was conducted with juvenile fish of 18 g initial body weight fed either a fish oil-based diet (FO diet) or vegetable oils replacing 33% (33VO) and 66% (66VO) of fish oil. The trial included 3 months feeding a fish oil finishing diet to follow the restoration of the FA profile with the FO diet. Fish oil replacement with/without a finishing phase of fish oil re-feeding did not affect growth and all groups reached 520-531 g body weight. Changes in body composition with weight gain did not modify the FA profile of fish continuously fed FO, 33VO or 66VO diets. Increased amounts of oleic acid (18:1n−9), linoleic acid (18:2n−6) and linolenic acid (18:3n−3), in combination with reduced proportions of n−3 long chain polyunsaturated FAs, were found with the partial replacement of fish oil. Hence, multivariate component analysis highlighted a gradient of fish oil load determined by the total intake of fish oil over the entire production cycle. The simple dilution model was a good descriptor of these tissue FA changes, and excellent correlations between observed and predicted values were found at the end of finishing period in fish grow out with either 33VO or 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.…”

Potential, Implications and Solutions Regarding the Use of Rendered Animal Fats in Aquafeeds

“…Although alternative lipids, including rendered fats, can be readily incorporated into aquafeeds, the resultant seafood products will contain less of the beneficial LC-PUFA. To balance the conflicting demands to reduce reliance on marine-derived lipids while maintaining product quality, aquaculture nutritionists have begun investigating the use of finishing feeds to compensate for the effects of alternative lipids on fillet fatty acid profile [81][82][83][84][85][86][87][88][89][90][91][92] . In these strategies, fish are raised on a low LC-PUFA content, alternative lipid based grow-out feed for a majority of the production cycle and then are switched to a high LC-PUFA content, fish oil-based finishing feed to modify fillet fatty acid profile immediately prior to harvest.…”

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“…However, in feeds for marine carnivorous fish the use of VO as a sole lipid source is limited by the high dietary requirements of these species LC-PUFA (Tocher, 2010;Benedito-Palos et al, 2009). The high requirements for LC-PUFA are due to the limited ability to these species of bioconvert C 18 polyunsaturated fatty acids (PUFA; namely linoleic acid -18:2n-6, LA-and α-linolenic acid -18:3n-3, ALA) into for LC-PUFA (namely arachidonic acid -20:4n-6, ARA-, eicosapentaenoic acid -20:5n-3, EPAand docosahexaenoic acid -22:6n-3, DHA) (Torstensen and Tocher, 2010).…”