6 Safe and Nutritious Aquaculture Produce
191
6.3.2 Effects of Fish Meal Replacement on Growth Performance
The investigation of fish meal substitutes to supply dietary protein in aquafeeds has
been conducted for many years, and although often driven by the desire for more
cost effective raw materials, more recently the focus has been to introduce more
sustainable aquaculture practices. Generally, despite lower protein content, lower
levels of some essential amino acids and the presence of anti-nutritional factors,
replacement of around 30% of fish meal can be achieved without loss of growth
performance, depending on the degree of product refinement (Teskeredzic et al.
1995; Medale et al. 1998; Glencross et al. 2004; Morris et al. 2005). Some trials
have been conducted with fish meal-free diets but generally these have resulted in
loss of growth performance (Kaushik et al. 1995; Watanabe et al. 1998). In recent
studies in rainbow trout, replacement of FM above 75% resulted in growth reduction as well as some changes in sensory properties, even though amino acid contents were optimized by addition of crystalline amino acids (de Francesco et al.
2004). However, this was a long term trial of almost 6 months and growth rates only
became depressed in the high plant protein group after 12 weeks, which is similar
to the length of many trials conducted on FM replacement and emphasizes the need
to conduct longer term trials (de Francesco et al. 2004).
Generally, Atlantic salmon appear less able to cope with high levels of plant
proteins than rainbow trout which may be related to different digestive capacity as
well as sensitivity to ANFs (Refstie et al. 2000; Glencross et al. 2004; Mundheim
et al. 2004). Salmon fed a range of plant protein concentrations, provided by full-fat
soya meal and maize gluten (2:1 w:w), from 15% to 65% showed a linear decrease
in growth with each addition of plant protein (Mundheim et al. 2004), although
there were no significant differences in SGR, TGC or FCR.
Diets replacing all fish meal with maize gluten and soy protein showed significant growth reduction in European sea bass (Dias 1999) compared to studies utilizing lower levels of replacement (Tibaldi et al. 1999; Tulli et al. 1999). A more
recent study, in which sea bass were fed up to 98% of dietary protein as plant meals,
showed no reduction of growth over a 12 week period (Kaushik et al. 2004), and,
unlike previous studies (Gomes et al. 1995; Dias 1999), there was no reduction of
voluntary feed intake in the study by Kaushik et al. (2004). In gilthead sea bream,
previous studies have indicated that about one third of the fish meal could be
replaced without reducing the levels of indispensable amino acids or reduction in
growth rate (Pereira and Oliva-Teles 2002; Gomez-Requeni et al. 2003). However,
in a more recent study over 12 weeks, sea bream showed a slight growth reduction
when 50 and 75% of protein was provided by plant sources but a 30% growth
reduction was seen at 100% plant protein inclusion and this was associated with a
marked reduction in feed intake (Gomez-Requeni et al. 2004). By contrast, a recent
longer term trial showed that 75% plant protein inclusion did not result in growth
reduction (Sitja-Bobadilla et al. 2005).
In turbot (Psetta maxima), studies with either maize gluten or lupin have shown
promising results as potential fish meal substitutes although reduced feed intake
was observed (Burel et al. 2000a,b). In an attempt to provide a more balanced
191
6.3.2 Effects of Fish Meal Replacement on Growth Performance
The investigation of fish meal substitutes to supply dietary protein in aquafeeds has
been conducted for many years, and although often driven by the desire for more
cost effective raw materials, more recently the focus has been to introduce more
sustainable aquaculture practices. Generally, despite lower protein content, lower
levels of some essential amino acids and the presence of anti-nutritional factors,
replacement of around 30% of fish meal can be achieved without loss of growth
performance, depending on the degree of product refinement (Teskeredzic et al.
1995; Medale et al. 1998; Glencross et al. 2004; Morris et al. 2005). Some trials
have been conducted with fish meal-free diets but generally these have resulted in
loss of growth performance (Kaushik et al. 1995; Watanabe et al. 1998). In recent
studies in rainbow trout, replacement of FM above 75% resulted in growth reduction as well as some changes in sensory properties, even though amino acid contents were optimized by addition of crystalline amino acids (de Francesco et al.
2004). However, this was a long term trial of almost 6 months and growth rates only
became depressed in the high plant protein group after 12 weeks, which is similar
to the length of many trials conducted on FM replacement and emphasizes the need
to conduct longer term trials (de Francesco et al. 2004).
Generally, Atlantic salmon appear less able to cope with high levels of plant
proteins than rainbow trout which may be related to different digestive capacity as
well as sensitivity to ANFs (Refstie et al. 2000; Glencross et al. 2004; Mundheim
et al. 2004). Salmon fed a range of plant protein concentrations, provided by full-fat
soya meal and maize gluten (2:1 w:w), from 15% to 65% showed a linear decrease
in growth with each addition of plant protein (Mundheim et al. 2004), although
there were no significant differences in SGR, TGC or FCR.
Diets replacing all fish meal with maize gluten and soy protein showed significant growth reduction in European sea bass (Dias 1999) compared to studies utilizing lower levels of replacement (Tibaldi et al. 1999; Tulli et al. 1999). A more
recent study, in which sea bass were fed up to 98% of dietary protein as plant meals,
showed no reduction of growth over a 12 week period (Kaushik et al. 2004), and,
unlike previous studies (Gomes et al. 1995; Dias 1999), there was no reduction of
voluntary feed intake in the study by Kaushik et al. (2004). In gilthead sea bream,
previous studies have indicated that about one third of the fish meal could be
replaced without reducing the levels of indispensable amino acids or reduction in
growth rate (Pereira and Oliva-Teles 2002; Gomez-Requeni et al. 2003). However,
in a more recent study over 12 weeks, sea bream showed a slight growth reduction
when 50 and 75% of protein was provided by plant sources but a 30% growth
reduction was seen at 100% plant protein inclusion and this was associated with a
marked reduction in feed intake (Gomez-Requeni et al. 2004). By contrast, a recent
longer term trial showed that 75% plant protein inclusion did not result in growth
reduction (Sitja-Bobadilla et al. 2005).
In turbot (Psetta maxima), studies with either maize gluten or lupin have shown
promising results as potential fish meal substitutes although reduced feed intake
was observed (Burel et al. 2000a,b). In an attempt to provide a more balanced