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J.G. Bell and R. Waagbø
studies that have used RO (Bell et al. 2001a, 2003a,b; Rosenlund et al. 2001) or LO
(Bell et al. 1997, 2003a; Tocher et al. 2000) as full, or partial, replacement of FO
and suggest that the energy requirements of salmon can be satisfied by VO with
variable fatty acid compositions. Furthermore, the lack of any negative growth
response suggests that the contribution of EPA and DHA from dietary fishmeal is
sufficient to satisfy EFA requirements of salmon up to 100% replacement of FO
with VO.
In a full production cycle trial in salmon, a dietary fatty acid composition was
formulated by mixing RO, LO and palm oil (PO) to provide similar levels of the
different fatty acid classes (saturated, monounsaturated and polyunsaturated n-3
fatty acids) to capelin oil. It was hoped this balance might be better physiologically
for fish health and welfare. Thus, at high levels of FO replacement (75 or 100%) a
balanced fatty acid composition should be less stressful physiologically compared
to the more extreme fatty acid compositions obtained by replacing FO with a single
VO. Thus, when salmon were fed either 75 or 100% of the VO blend for the whole
production cycle, at two different geographical locations, growth was high in all
treatments. However, for the 100% VO group in Norway, significantly higher final
mean weight was found compared to the FO group (Torstensen et al. 2005). The
higher mean weight after 22 months post-first feeding (PFF) correlated with higher
protein sparing in the 100% VO group compared to the FO group indicating that,
during the late autumn and winter period of the sea water growth phase, the fatty
acid composition of the 100% VO diet favoured protein growth and spared dietary
protein from energy production (Torstensen et al. 2005). Previously, dietary lipid
content, but not dietary oil source (Torstensen et al. 2000; Bendiksen et al. 2003),
has been shown to affect protein utilisation, growth rate, muscle lipid level and feed
conversion (Watanabe 1977; Arzel et al. 1993, 1994).
In rainbow trout fed the same single VOs as described for salmon, for 12 weeks,
or the 75% and 100% VO blend, for 62 weeks, there were no significant effects of
diet on final weight, SGR, TGC or FCR (Kaushik and Corraze 2004, Richard et al.
2006). This data supports earlier studies with rainbow trout and other salmonids
where no detrimental effects on growth were observed with different FO substitutes, including soybean oil (SO), RO, OO, PO, LO and lard (Dosanjh et al. 1988;
Greene and Selivonchick 1990; Guillou et al. 1995; Caballero et al. 2002;
Figueiredo-Silva et al. 2005; Fonseca-Madrigal et al. 2005). No increase in final
weight of rainbow trout fed the 100% VO blend was observed. In salmon, the beneficial growth effect during the winter period in Norway may have been due to
increased fatty acid digestibility, and thereby increased protein sparing, which lead
to improved growth at low water temperatures of less than 5°C. By contrast, the
rainbow trout trial was conducted at a constant 17°C where any differences in
digestibility at low temperature would not be apparent (Ng et al. 2004a).
In sea bass and sea bream, replacement of up to 60% of FO with VO had no
detrimental effects on growth or feed conversion (Izquierdo et al. 2003, 2005;
Mourente et al. 2005). However, replacement with 80% linseed oil or 100% of a VO
blend in sea bream did reduce growth rates (Izquierdo et al. 2003, 2005) although,
with the VO blend, growth reduction was not seen in fish over 250 g suggesting that
EFA requirements in larger fish were less stringent than in smaller fish.
J.G. Bell and R. Waagbø
studies that have used RO (Bell et al. 2001a, 2003a,b; Rosenlund et al. 2001) or LO
(Bell et al. 1997, 2003a; Tocher et al. 2000) as full, or partial, replacement of FO
and suggest that the energy requirements of salmon can be satisfied by VO with
variable fatty acid compositions. Furthermore, the lack of any negative growth
response suggests that the contribution of EPA and DHA from dietary fishmeal is
sufficient to satisfy EFA requirements of salmon up to 100% replacement of FO
with VO.
In a full production cycle trial in salmon, a dietary fatty acid composition was
formulated by mixing RO, LO and palm oil (PO) to provide similar levels of the
different fatty acid classes (saturated, monounsaturated and polyunsaturated n-3
fatty acids) to capelin oil. It was hoped this balance might be better physiologically
for fish health and welfare. Thus, at high levels of FO replacement (75 or 100%) a
balanced fatty acid composition should be less stressful physiologically compared
to the more extreme fatty acid compositions obtained by replacing FO with a single
VO. Thus, when salmon were fed either 75 or 100% of the VO blend for the whole
production cycle, at two different geographical locations, growth was high in all
treatments. However, for the 100% VO group in Norway, significantly higher final
mean weight was found compared to the FO group (Torstensen et al. 2005). The
higher mean weight after 22 months post-first feeding (PFF) correlated with higher
protein sparing in the 100% VO group compared to the FO group indicating that,
during the late autumn and winter period of the sea water growth phase, the fatty
acid composition of the 100% VO diet favoured protein growth and spared dietary
protein from energy production (Torstensen et al. 2005). Previously, dietary lipid
content, but not dietary oil source (Torstensen et al. 2000; Bendiksen et al. 2003),
has been shown to affect protein utilisation, growth rate, muscle lipid level and feed
conversion (Watanabe 1977; Arzel et al. 1993, 1994).
In rainbow trout fed the same single VOs as described for salmon, for 12 weeks,
or the 75% and 100% VO blend, for 62 weeks, there were no significant effects of
diet on final weight, SGR, TGC or FCR (Kaushik and Corraze 2004, Richard et al.
2006). This data supports earlier studies with rainbow trout and other salmonids
where no detrimental effects on growth were observed with different FO substitutes, including soybean oil (SO), RO, OO, PO, LO and lard (Dosanjh et al. 1988;
Greene and Selivonchick 1990; Guillou et al. 1995; Caballero et al. 2002;
Figueiredo-Silva et al. 2005; Fonseca-Madrigal et al. 2005). No increase in final
weight of rainbow trout fed the 100% VO blend was observed. In salmon, the beneficial growth effect during the winter period in Norway may have been due to
increased fatty acid digestibility, and thereby increased protein sparing, which lead
to improved growth at low water temperatures of less than 5°C. By contrast, the
rainbow trout trial was conducted at a constant 17°C where any differences in
digestibility at low temperature would not be apparent (Ng et al. 2004a).
In sea bass and sea bream, replacement of up to 60% of FO with VO had no
detrimental effects on growth or feed conversion (Izquierdo et al. 2003, 2005;
Mourente et al. 2005). However, replacement with 80% linseed oil or 100% of a VO
blend in sea bream did reduce growth rates (Izquierdo et al. 2003, 2005) although,
with the VO blend, growth reduction was not seen in fish over 250 g suggesting that
EFA requirements in larger fish were less stringent than in smaller fish.