FISH NUTRITION
475
suitable for fish farming in the U.K. Results with two soles (Solea
solea) held individually were less promising.
Colman (1970) obtained conversion efficiencies similar to those of
Edwards et al. (1970) when plaice were fed mussel flesh-26% on average
in short term experiments at 15°C. Mussel flesh contains 10% protein
(Bowers and Landless, 1969) and as 5 g mussel (0-5g protein) were
needed to produce 1 g live weight gain the PER was 2.0. Artificial
diets containing freeze dried cod muscle gave a PER of 1-8 when fed to
plaice (Cowey et al., 1971) but similar diets containing other protein
sources (leaf protein concentrate, soya bean meal, single cell protein)
gave lower PERs.
VIII. LEAST-COST FORMULATION
In recent years least cost formulation procedures have been used
for production diets. The diet is defined by allowances of a number of
essential nutrients. Ingredients are then selected by means of a
suitably programmed computer on the dual scores of the cost of the
raw materials and their content of these nutrients. For example, combinations of materials which will supply not less than the desired
amount of say six or seven amino acids are thus chosen. So a number
of nutritional parameters are met in the cheapest possible way. This
method has much to recommend it and appears to have been successfully used for catfish diets by Deyoe and Tiemeier (1968).
The method may have some complications. A fairly simple set of
instructions are needed relating the content of the defined nutrient in
each raw material to that in the diet formulation. If all ten essential
amino acids are not t o be included in the instructions the question of
which may be safely omitted arises. The requirements for certain
amino acids may increase in the presence of large amounts of other
amino acids. Factors for the more limited digestibility of some proteins
(especially those of vegetable origin) may have to be inserted into the
programme, and it seems desirable to apply corrections for non-availability or low availability of certain amino acids in some materials.
Leucine/isoleucine antagonism (Chance et al., 1964) may pose a
particular difficulty.
The procedure is not as straightforward as might appear at fist
sight and in practice seems to lead to rations with high contents of
materials of vegetable origin. These are not ideal for carnivorous fish
(Cowey et at., 1971).
475
suitable for fish farming in the U.K. Results with two soles (Solea
solea) held individually were less promising.
Colman (1970) obtained conversion efficiencies similar to those of
Edwards et al. (1970) when plaice were fed mussel flesh-26% on average
in short term experiments at 15°C. Mussel flesh contains 10% protein
(Bowers and Landless, 1969) and as 5 g mussel (0-5g protein) were
needed to produce 1 g live weight gain the PER was 2.0. Artificial
diets containing freeze dried cod muscle gave a PER of 1-8 when fed to
plaice (Cowey et al., 1971) but similar diets containing other protein
sources (leaf protein concentrate, soya bean meal, single cell protein)
gave lower PERs.
VIII. LEAST-COST FORMULATION
In recent years least cost formulation procedures have been used
for production diets. The diet is defined by allowances of a number of
essential nutrients. Ingredients are then selected by means of a
suitably programmed computer on the dual scores of the cost of the
raw materials and their content of these nutrients. For example, combinations of materials which will supply not less than the desired
amount of say six or seven amino acids are thus chosen. So a number
of nutritional parameters are met in the cheapest possible way. This
method has much to recommend it and appears to have been successfully used for catfish diets by Deyoe and Tiemeier (1968).
The method may have some complications. A fairly simple set of
instructions are needed relating the content of the defined nutrient in
each raw material to that in the diet formulation. If all ten essential
amino acids are not t o be included in the instructions the question of
which may be safely omitted arises. The requirements for certain
amino acids may increase in the presence of large amounts of other
amino acids. Factors for the more limited digestibility of some proteins
(especially those of vegetable origin) may have to be inserted into the
programme, and it seems desirable to apply corrections for non-availability or low availability of certain amino acids in some materials.
Leucine/isoleucine antagonism (Chance et al., 1964) may pose a
particular difficulty.
The procedure is not as straightforward as might appear at fist
sight and in practice seems to lead to rations with high contents of
materials of vegetable origin. These are not ideal for carnivorous fish
(Cowey et at., 1971).