476
0. B. UOWEY AND J. R. SARQENT
IX. PERSPECTIVES
The great advances in enzymology and other branches of biochemistry during the last thirty years or so have vastly increased our
understanding of previously obscure mechanisms of life processes, and
have revealed the true nature of many nutritional problems. Thus
our present day knowledge of the way in which food components are
made available to the body and are transferred and metabolized
between and within cells has resolved many nutritional issues and
brought others into sharper relief. I n fact nutritional requirements
cannot be divorced from biochemical functions.
Some biochemical knowledge is qualitative rather than quantitative,
in the sense that while the detailed steps and mechanisms of interconnecting metabolic pathways are well known, the factors concerned
with determining the overall rates of metabolic fluxes are only now
beginning to be unravelled. The quantitative aspects of metabolism
are particularly important to nutrition because the latter science is
frequently concerned with maximizing the rates of interconnecting
metabolic systems to produce an optimal growth rate in animals. That
is, one major objective in animal nutrition is to balance the individual
constituents of a diet to achieve optimal performance in those
metabolic systems involved in growth. A detailed understanding of
metabolic control phenomena is basic to this aim.
For the most part biochemical knowledge has been gained from
experiments with mammals and bacteria. Clearly a full appreciation
of the nutrition of fish demands a more intensive concern with fish
biochemistry than has been shown in the past.
For example, it is plain that the overwhelming majority of fish
normally use carbohydrate to only a limited extent for energy provision, but instead show a strong tendency to metabolize protein
especially when feeding on natural, protein-rich diets. Protein oxidation
is nutritionally and economically wasteful and, in considering the interplay of dietary factors, efforts to direct metabolism towards the oxidation of lipid or carbohydrate rather than protein should be pursued.
The underlying reasons for lipid storage and protein oxidation under
some circumstances, and for lipid mobilization and utilization under
others (e.g. during migration) need to be defined and resolved.
Many other overall aspects of metabolism in fish, which bear closely
on nutrition, are not presently understood. Thus the combined roles of
liver and adipose tissue in a single organ may involve different
hormonal controls from those found in mammals. The relationships
between protein, lipid and carbohydrate in gluconeogenesis and in
0. B. UOWEY AND J. R. SARQENT
IX. PERSPECTIVES
The great advances in enzymology and other branches of biochemistry during the last thirty years or so have vastly increased our
understanding of previously obscure mechanisms of life processes, and
have revealed the true nature of many nutritional problems. Thus
our present day knowledge of the way in which food components are
made available to the body and are transferred and metabolized
between and within cells has resolved many nutritional issues and
brought others into sharper relief. I n fact nutritional requirements
cannot be divorced from biochemical functions.
Some biochemical knowledge is qualitative rather than quantitative,
in the sense that while the detailed steps and mechanisms of interconnecting metabolic pathways are well known, the factors concerned
with determining the overall rates of metabolic fluxes are only now
beginning to be unravelled. The quantitative aspects of metabolism
are particularly important to nutrition because the latter science is
frequently concerned with maximizing the rates of interconnecting
metabolic systems to produce an optimal growth rate in animals. That
is, one major objective in animal nutrition is to balance the individual
constituents of a diet to achieve optimal performance in those
metabolic systems involved in growth. A detailed understanding of
metabolic control phenomena is basic to this aim.
For the most part biochemical knowledge has been gained from
experiments with mammals and bacteria. Clearly a full appreciation
of the nutrition of fish demands a more intensive concern with fish
biochemistry than has been shown in the past.
For example, it is plain that the overwhelming majority of fish
normally use carbohydrate to only a limited extent for energy provision, but instead show a strong tendency to metabolize protein
especially when feeding on natural, protein-rich diets. Protein oxidation
is nutritionally and economically wasteful and, in considering the interplay of dietary factors, efforts to direct metabolism towards the oxidation of lipid or carbohydrate rather than protein should be pursued.
The underlying reasons for lipid storage and protein oxidation under
some circumstances, and for lipid mobilization and utilization under
others (e.g. during migration) need to be defined and resolved.
Many other overall aspects of metabolism in fish, which bear closely
on nutrition, are not presently understood. Thus the combined roles of
liver and adipose tissue in a single organ may involve different
hormonal controls from those found in mammals. The relationships
between protein, lipid and carbohydrate in gluconeogenesis and in