208
J.G. Bell and R. Waagbø
23-week feeding study on the impact of dietary pro- and antioxidants on product
quality and health of adult Atlantic salmon, feed vitamins E (α-tocopherol acetate)
and C (ascorbate polyphosphate) supplementations of 69 and 430 mg/kg, and 52 and
1940 mg/kg, respectively, increased fillet α-tocopherol three fold (from 12–31 µg/g)
and vitamin C two fold (15–31 µg/g), respectively (Waagbø unpublished data). In the
same study, flesh astaxanthin varied two fold (1.3–2.5 µg/g), when salmon were fed
diets containing 11 or 48 mg astaxanthin/kg (Hamre et al. 2004). Even though the
flesh concentrations of antioxidant vitamins reflected the respective dietary levels,
fillet α-tocopherol alone was the major determinant of oxidative stability after an in
vitro oxidative challenge of muscle tissue (Hamre et al. 2004). The antioxidant
nutrients occur normally at low concentrations in feed ingredients (Table 6.3), and
even more may be lost through heat treatment and refining procedures. Therefore,
these are routinely supplied in fish feed production through stabilized additives.
There are no indications of increased requirement for these antioxidants when using
FM and FO substitutes. Indeed, some vegetable oils contain plant derived
antioxidants (vitamin E, carotenoids and xanthophylls), as well as n-3 PUFA less
susceptible to oxidation which can reduce the oxidative challenge in feed and tissues
(Hertrampf and Piedad-Pascual 2000; Ng et al. 2004b).
6.9 The Impact of Vegetable Oil Inclusion on Organic
Contaminant Concentrations in Salmon Flesh
Polychlorinated dibenzodioxins and polychlorinated dibenzofurans, collectively
known as dioxins, can arise from natural processes such as forest fires and
incomplete combustion of organic matter, as well as from industrial processes. The
dioxin-like polychlorinated biphenyls (DL-PCBs) are synthetic products used in
electrical transformers, heat exchange fluids, hydraulic oils and plastic manufacturing.
Although production of PCBs is now banned, they have been deposited in the
oceanic benthos, due to industrial activity over the last century, and they are widely
distributed across the marine biota (North Sea Task Force 1993). Dioxins and
DL-PCBs are highly lipophilic with biological half-lives of several decades, which
means they can accumulate in predators at the top of the food chain (Froescheis
et al. 2000). However, levels of both dioxins and PCBs in the environment have
been declining since the 1950s, although, due to their persistent nature, they will remain
in the biota for a considerable period (Brevik et al. 1990; Bignert et al. 1998).
There are around 210 known dioxin and furan congeners and, of these, 17 have
been shown to be toxic although individual congeners have different levels of
toxicity. For this reason the World Health Organisation (WHO) have established
toxic equivalency factors (TEFs), according to their relative toxicity, enabling the
calculation of toxic equivalents (TEQs; Van den Berg et al. 1998). Similarly, of the
209 PCB congeners 12 have known dioxin-like toxicity and have been assigned
WHO-TEQs. In 2001 the EU introduced new limits on dioxins and furans in fish
feeds and fish for human consumption (SCAN 2000; SCF 2001). These values are
J.G. Bell and R. Waagbø
23-week feeding study on the impact of dietary pro- and antioxidants on product
quality and health of adult Atlantic salmon, feed vitamins E (α-tocopherol acetate)
and C (ascorbate polyphosphate) supplementations of 69 and 430 mg/kg, and 52 and
1940 mg/kg, respectively, increased fillet α-tocopherol three fold (from 12–31 µg/g)
and vitamin C two fold (15–31 µg/g), respectively (Waagbø unpublished data). In the
same study, flesh astaxanthin varied two fold (1.3–2.5 µg/g), when salmon were fed
diets containing 11 or 48 mg astaxanthin/kg (Hamre et al. 2004). Even though the
flesh concentrations of antioxidant vitamins reflected the respective dietary levels,
fillet α-tocopherol alone was the major determinant of oxidative stability after an in
vitro oxidative challenge of muscle tissue (Hamre et al. 2004). The antioxidant
nutrients occur normally at low concentrations in feed ingredients (Table 6.3), and
even more may be lost through heat treatment and refining procedures. Therefore,
these are routinely supplied in fish feed production through stabilized additives.
There are no indications of increased requirement for these antioxidants when using
FM and FO substitutes. Indeed, some vegetable oils contain plant derived
antioxidants (vitamin E, carotenoids and xanthophylls), as well as n-3 PUFA less
susceptible to oxidation which can reduce the oxidative challenge in feed and tissues
(Hertrampf and Piedad-Pascual 2000; Ng et al. 2004b).
6.9 The Impact of Vegetable Oil Inclusion on Organic
Contaminant Concentrations in Salmon Flesh
Polychlorinated dibenzodioxins and polychlorinated dibenzofurans, collectively
known as dioxins, can arise from natural processes such as forest fires and
incomplete combustion of organic matter, as well as from industrial processes. The
dioxin-like polychlorinated biphenyls (DL-PCBs) are synthetic products used in
electrical transformers, heat exchange fluids, hydraulic oils and plastic manufacturing.
Although production of PCBs is now banned, they have been deposited in the
oceanic benthos, due to industrial activity over the last century, and they are widely
distributed across the marine biota (North Sea Task Force 1993). Dioxins and
DL-PCBs are highly lipophilic with biological half-lives of several decades, which
means they can accumulate in predators at the top of the food chain (Froescheis
et al. 2000). However, levels of both dioxins and PCBs in the environment have
been declining since the 1950s, although, due to their persistent nature, they will remain
in the biota for a considerable period (Brevik et al. 1990; Bignert et al. 1998).
There are around 210 known dioxin and furan congeners and, of these, 17 have
been shown to be toxic although individual congeners have different levels of
toxicity. For this reason the World Health Organisation (WHO) have established
toxic equivalency factors (TEFs), according to their relative toxicity, enabling the
calculation of toxic equivalents (TEQs; Van den Berg et al. 1998). Similarly, of the
209 PCB congeners 12 have known dioxin-like toxicity and have been assigned
WHO-TEQs. In 2001 the EU introduced new limits on dioxins and furans in fish
feeds and fish for human consumption (SCAN 2000; SCF 2001). These values are