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J.G. Bell and R. Waagbø
amino acid composition Fournier et al. (2004) fed a mixture of lupin, wheat and
maize gluten with supplementary crystalline amino acids and showed that growth
rate in turbot was only compromised when fed 90 or 100% replacement of fish meal
over 12 weeks.
The inclusion of high levels of plant proteins can be limited by the presence of
ANFs including protease inhibitors, phytates, glucosinolates, tannins, lectins,
phytoestrogens and antivitamins among others (Francis et al. 2001). At levels of
individual product inclusion in fish feeds many of these factors should not affect
growth performance and some can be reduced or eliminated by solvent extraction,
steam extrusion or enzymatic treatment. These anti-nutritional factors can reduce
growth by affecting palatability and reduction of feed intake or by limited digestibility.
Besides, these direct effects on nutrient supply and utilisation, indirect toxic effects
with organ damage and endocrine disruption are evident for some ANFs. Increased
use of plant proteins in aquafeeds requires more information on which factors are
present in specific plant meals so that measures to limit their effects can be achieved
by appropriate processing techniques.
A further concern regarding plant proteins is the presence of genetically modified (GM) products, currently used in terrestrial animal production, especially those
derived from soya, canola and maize (Pusztai and Bardocz 2006). However, studies
conducted with Atlantic salmon suggest that while short transgenic sequences
(~120 bp) can be detected in gut tissues, no transgenic fragments have been found
in liver, muscle or brain (Sanden et al. 2004). For this reason, there should be no
danger of transgenic plant material entering the human food chain from consumption of farmed salmon flesh.
6.3.3 Flesh Fatty Acid Compositions Including Success
of Finishing Diets
Numerous studies, in a wide range of fish species, have shown that flesh fatty acid
compositions are closely correlated to dietary fatty acid compositions and that feeding high levels of VO will strongly influence flesh fatty acid compositions (Bell
et al. 2004a; Izquierdo et al. 2003; Caballero et al. 2002; Mourente et al. 2005;
Visentainer et al. 2005; Glencross et al. 2003). However, the influence of dietary
lipid on flesh fatty acids is also related to the lipid content of the flesh and the ratio
of neutral to polar lipid present, since the correlation with diet is closest in lipid rich
flesh, which is high in neutral lipid, especially triacylglycerols (Sargent et al. 2002).
In this regard, the rank order of flesh lipid content would be salmon > trout > sea
bream > sea bass > cod and flesh lipid deposition tends to increase with fish weight,
especially in salmonids (Hemre and Sandnes 1999; Torstensen et al. 2001). Several
studies with salmon have shown a clear linear relationship between dietary and
flesh fatty acid compositions where a number of VO including RO, PO, SO and
blends of RO and LO have been used, along with FO, in diet formulations
(Rosenlund et al. 2001; Torstensen et al. 2001, 2004a; Bell et al. 2001a, 2002, 2003a).
J.G. Bell and R. Waagbø
amino acid composition Fournier et al. (2004) fed a mixture of lupin, wheat and
maize gluten with supplementary crystalline amino acids and showed that growth
rate in turbot was only compromised when fed 90 or 100% replacement of fish meal
over 12 weeks.
The inclusion of high levels of plant proteins can be limited by the presence of
ANFs including protease inhibitors, phytates, glucosinolates, tannins, lectins,
phytoestrogens and antivitamins among others (Francis et al. 2001). At levels of
individual product inclusion in fish feeds many of these factors should not affect
growth performance and some can be reduced or eliminated by solvent extraction,
steam extrusion or enzymatic treatment. These anti-nutritional factors can reduce
growth by affecting palatability and reduction of feed intake or by limited digestibility.
Besides, these direct effects on nutrient supply and utilisation, indirect toxic effects
with organ damage and endocrine disruption are evident for some ANFs. Increased
use of plant proteins in aquafeeds requires more information on which factors are
present in specific plant meals so that measures to limit their effects can be achieved
by appropriate processing techniques.
A further concern regarding plant proteins is the presence of genetically modified (GM) products, currently used in terrestrial animal production, especially those
derived from soya, canola and maize (Pusztai and Bardocz 2006). However, studies
conducted with Atlantic salmon suggest that while short transgenic sequences
(~120 bp) can be detected in gut tissues, no transgenic fragments have been found
in liver, muscle or brain (Sanden et al. 2004). For this reason, there should be no
danger of transgenic plant material entering the human food chain from consumption of farmed salmon flesh.
6.3.3 Flesh Fatty Acid Compositions Including Success
of Finishing Diets
Numerous studies, in a wide range of fish species, have shown that flesh fatty acid
compositions are closely correlated to dietary fatty acid compositions and that feeding high levels of VO will strongly influence flesh fatty acid compositions (Bell
et al. 2004a; Izquierdo et al. 2003; Caballero et al. 2002; Mourente et al. 2005;
Visentainer et al. 2005; Glencross et al. 2003). However, the influence of dietary
lipid on flesh fatty acids is also related to the lipid content of the flesh and the ratio
of neutral to polar lipid present, since the correlation with diet is closest in lipid rich
flesh, which is high in neutral lipid, especially triacylglycerols (Sargent et al. 2002).
In this regard, the rank order of flesh lipid content would be salmon > trout > sea
bream > sea bass > cod and flesh lipid deposition tends to increase with fish weight,
especially in salmonids (Hemre and Sandnes 1999; Torstensen et al. 2001). Several
studies with salmon have shown a clear linear relationship between dietary and
flesh fatty acid compositions where a number of VO including RO, PO, SO and
blends of RO and LO have been used, along with FO, in diet formulations
(Rosenlund et al. 2001; Torstensen et al. 2001, 2004a; Bell et al. 2001a, 2002, 2003a).