February 15-18, 2009 Washington State Convention Center Seattle ...

MODELLING OF NUTRITIONAL REQUIREMENTS IN AQUATIC SPECIES
Ingrid Lupatsch
Centre for Sustainable Aquaculture Research
Swansea University
Singleton Park
Swansea SA2 8PP, UK
i.lupatsch@swansea.ac.uk
Modelling of nutritional requirements is a mathematical setup used to predict and improve growth performance and feed efficiency
of the target species. A suitable model is ideally based on mathematical relationships that should be as simple as possible
but be able to supply reliable data for practical application.
In classical nutrition the requirements are separated into two components, first the amount of energy and protein needed to
maintain zero balance and the other component the energy and protein needed for growth above maintenance. Thus total energy
and protein requirements are considered the sum of maintenance plus growth. The requirement for maintenance is mainly a
function of the size of the fish and water temperature, and is proportional to the metabolic body weight. The requirement for
growth is dependent on the amount and the composition of the weight gain, including the energetic cost to deposit the new
growth.
The following equation specifies the formal approach to those calculations:
Requirement = a × BW (kg) b + c × gain
(kg) b : Metabolic body weight
a is the constant for given conditions (activity, temperature) expressed in kJ per unit of metabolic weight and characteristic of
a fish species
b is the exponent of the metabolic body weight and converts absolute weight to metabolic weight correcting for the decrease in
metabolic rate per unit of body weight as fish grow.
c - cost in units of energy or protein to deposit new growth.
Mathematical equations based on empirical studies will be presented to derive the necessary parameters to define:
• Maintenance requirements for energy and protein at different water temperatures
• Growth data – a description of the potential weight gain along the growth cycle at different temperatures.
• Feed intake - a prediction of the voluntary feed intake at increasing fish sizes and water temperatures.
• Description of protein and energy content with increasing fish size.
• Efficiency of utilization of dietary energy and protein to deposit energy and protein as growth.
Feeds can then be formulated and feeding tables established which are based on daily requirements for energy and protein
dependent on anticipated growth of the fish species in question.
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