Restoration of the fatty acid composition of red seabream (Pagrus auratus) using a fish oil finishing diet after grow-out on plant oil based diets

Abstract

This study evaluated the potential for manipulating the fatty acid composition of juvenile red seabream, Pagrus auratus. Prior to the start of the study, three groups of fish had been reared for 3 months on a fish oil based diet or diets where the added fish oil had been replaced with either canola or soybean oil. In the present study, fish that had previously been fed either the canola or soybean oil diets were fed a fish oil based diet. Three additional treatments included fish being maintained on their original diets of fish oil, canola oil or soybean oil. Fish were fed their respective diets twice daily to apparent satiety for 32 days. Samples of fish from each treatment were collected after 0, 1, 2, 4, 8, 16 and 32 days. Composition and growth of the fish were determined at each sample point. Most treatments showed no differences in growth performance, although fish fed a fish oil diet after previously being fed a soybean oil diet showed slightly better growth. No significant differences among treatments were observed in proximate composition of the fish, although there was a significant increase in total fat and individual fatty acid (g kg )1 live-weight) content of the fish from all treatments over the period of the study. No significant changes in the relative fatty acid composition (% of total fatty acids) over time were observed in the three treatments where fish were maintained on their original diets. In contrast, fish that were previously fed either the canola or soybean oil diets and were then fed a fish oil diet had significant changes in both the relative (% of total fatty acids) and absolute (g kg )1 live-weight) fatty acid content. Key changes observed included a decrease in the relative levels of polyunsaturated fatty acids (PUFA) such as 18 : 2n ) 6 and 18 : 3n ) 3. Increases in the relative levels of the long-chain polyunsaturated fatty acids (lcPUFA) 20 : 5n ) 3 and 22 : 6n ) 3 were also observed in both treatments. The rates of absolute (g kg )1 live-weight) change/accumulation of these fatty acids followed an exponential equation that differed for each fatty acid in each treatment. Examination of the retention efficiency of specific fatty acids also showed marked differences between fatty acids within treatments and also differences between treatments. Biologically important fatty acids such as 20 : 5n ) 3 and 22 : 6n ) 3 had only moderate retention efficiencies and these were unaffected by treatment. In contrast, the retention efficiencies of 18 : 2n ) 6 and 18 : 3n ) 3 suggested selective retention of these fatty acids when fed fish oil diets, but moderate catabolism when fed the plant oil diets. There were also high retention efficiencies of most saturated and monounsaturated fatty acids suggestive of active retention and/or active synthesis of these fatty acids by the fish. The results of this study, particularly the increases in lcPUFA, support the usefulness of a fish oil based finisher diet for fish raised predominantly on plant oil based diets. KEY WORDS

Eicosapentaenoic Acid, Arachidonic Acid and Eicosanoid Metabolism in Juvenile Barramundi Lates calcarifer

“…In addition, the EPA retention figures were modest with a calculated intake to gain ratio of 1.6:1 confirming this. This is consistent with other studies on barramundi and red sea bream in that EPA is only modestly retained unless there is a gross imbalance of other LC-PUFA (Glencross et al, 2003b;Glencross and Rutherford, 2011).…”

Untitled

“…After the eighth week of study, growth performance, especially in terms of SGR values, were in agreement with previous studies (Piedecausa et al, 2007;Sa et al, 2008a,b;Arslan et al, 2012;Wassef et al, 2014). Results in terms of growth and feed utilization were similar to those of previous studies of fish oil replacement with soybean oil and canola oil (Rosenlund et al, 2001;Caballero et al, 2002;Piedecausa et al, 2007;Fountoulaki et al, 2009;Arslan et al, 2012;Han et al, 2013;Glencross et al, 2003;Stubhaug et al, 2007;Huang et al, 2007;Fountoulaki et al, 2009;Karayücel and Dernekbaşı, 2010;Taşbozan et al, 2014b) on different fish species. Arslan et al (2012) did not achieve a better growth with the usage of hazelnut oil instead of fish oil in brown trout.…”

Effects of Nutrition and Aquaculture Practices on Fish Quality

“…A well-established rule is that muscle fatty acids of the fish reflect the dietary fatty acids, and this has been confirmed for most of the aquacultured fish species, including salmonids [9,37], Mediterranean species [36,38], carps [7], cod [35], catfish species [6], and flatfish [34]. Therefore, manipulation of the fatty acid profile of the end-product can be achieved.…”