Atlantic salmon, Salmo salar, utilizes wax ester-rich oil from Calanus finmarchicus effectively

Abstract

'Atlantic salmon, Salmo salar, utilizes wax ester-rich oil from Calanus finmarchicus effectively' by R. E. Olsen, R. J. Henderson, J. Suotonama, G. AbstractAgainst a background of decreasing availability of fish oils for use in aquaculture, the present study was undertaken to examine whether a wax ester -rich oil derived from the calanoid copepod Calanus finmarchicus, could be used effectively by Atlantic salmon when supplied in their diet. Individually tagged Atlantic salmon of initial weight around 500g were divided into replicate tanks of two dietary groups and fed either a fish oil supplemented diet, or an experimental diet coated with Calanus oil. Wax esters accounted for 37.5% of the lipids in the Calanus oil diet but were absent from the fish oil diet in which triacylglycerols (TAG) were the major lipid class. Over the feeding period (140 days) the salmon fed fish oil displayed a greater increase in length, but there was no significant difference between the two groups in weight gained. The specific growth rates (0.75) and the feed conversion ratio of fish fed the two diets were similar throughout the study.No differences were observed in the apparent digestibility coefficients (ADC) of fish fed Calanus oil or fish oil. The ADC of fatty acids decreased with chain length and increased with unsaturation. Long-chain alcohol utilization showed a similar tendency although there was a notable difference in that saturated long-chain alcohols were utilized better than the comparable fatty acid homologue. In fecal lipid of fish fed Calanus oil, the content of 16:0 alcohol decreased in both the free long-chain alcohol and wax ester fractions, while the corresponding fatty acid increased in the feces of both dietary groups of fish. In contrast, the proportion of the 22:1n-11 alcohol increased in both fecal wax esters and free long-chain alcohol fractions whereas 22:1n-11 fatty acid displayed no accumulation. The observed patterns of fatty acid and long-chain alcohol compositions in fecal lipid compared to those of the initial dietary lipid are consistent with the digestive lipases of salmon preferentially hydrolyzing esters containing PUFA moieties. The wax esters of Calanus oil contained substantial amounts of the n-3 PUFA, 20:5n-3 and 22:6n-3, that were effectively deposited in muscle and liver tissues. No major differences were seen in either lipid content/lipid classes or in gross fatty acid composition of these tissues between the two dietary groups. It is concluded that that Atlantic salmon in seawater can effectively utilize diets in which a major lipid component is derived from zooplankton rich in wax ester without any detrimental change in growth or body lipid composition. This finding gives support to the use of lipid from zooplankton from high latitudes as an alternative or as a supplement to fish oil and a provider of long chain n-3 PUFA in diets for use in salmon aquaculture.

Linking lipid dynamics with the reproductive cycle in Baltic cod Gadus morhua

“…This is consistent with SFAs being predominantly mobilized for metabolic purposes, whereas 18:1 (Weber et al 2003) and PUFAs are mainly retained (Sargent et al 2002, Dalsgaard & St John 2004. Furthermore, low SFAs can be due to low assimilation, because the digestibility of fatty acids decreases with saturation (Koven et al 1994, Olsen et al 2004). The average proportion of 18:1n-9 and DHA in cod liver compared to proportions in sprat and herring indicated a mixed diet consisting of these 2 clupeids.…”

Omega-3 long-chain polyunsaturated fatty acids and aquaculture in perspective

“…Copepods have an additional problem, as the oil is rich in wax esters rather than TAG, which may limit its widespread use (Olsen et al, 2004;Bogevik et al, 2010).…”

Use of fatty acid profiles to monitor the escape history of farmed Atlantic salmon

“…TAGs were separated from the total lipid by high-performance thin-layer chromatography (HPTLC) using the neutral solvent system of Olsen & Henderson (1989). All samples were methylated, and the respective fatty acid methyl esters (FAME) were analysed on a HP-7890A gas chromatograph (Agilent) with a flame ionization detector (GC-FID) as described previously in Olsen et al (2004) for the feeding experiment, and in Meier et al (2006) for the field trial. In total, 61 well-defined peaks in the chromatogram were selected, and identified by comparing retention times with a FAME standard (GLC-463 from Nu-Chek Prep) and retention index maps and mass spectral libraries (GC-MS) (www.chrombox.…”