Agriculture Reference
In-Depth Information
and mechanistic models of animal systems
is at best blurred.
Table 1.1
lists some em-
pirical models that have been published to
assist with decisions about flock structure
and replacement, nutrition, the environ-
ment, management and processing. This is
not a comprehensive list but has been
chosen to illustrate the many possibilities of
using this type of model.
of certain amounts of amino acids per unit
weight of maintenance plus definite
additional quantities for productive
increases such as units of growth and
quantity of eggs. Meeting these minimum
needs will be materially influenced by food
consumption.
This elegant conceptual theory provides,
at one level, a virtually complete model of
the system being described. It contains
mechanistic ideas that can be tested inde-
pendently of the whole model, it makes
the important distinction between bio-
logical systems described at the level of the
individual animal and the behaviour of
populations, and it refers to marginal eco-
nomic analysis. The same ideas were later
used by Fisher
et al
. (1973) in proposing a
model to describe the response of laying
hens to amino acid intake; a model that be-
came widely known as the 'Reading model'.
This was a more formal (and independent)
statement of Heuser's ideas and allowed a
Mechanistic models of poultry
production systems
In 1941 Heuser published a review of pro-
tein requirements of poultry. In the discus-
sion of the paper he wrote as follows:
the requirement is for the various amino
acids. . . In practice it is necessary to meet
the requirements of as many of the
individuals as we can economically. . .
The actual need is probably on the basis
Table 1.1.
Empirical models of poultry management systems.
Ref
a
System modelled
Type of model
Notes
Flock planning and replacement
1
Flock replacement in egg production
Dynamic programming
2
Broiler production; killing age
according to price
Econometric analysis
3
Optimum slaughter age turkeys
Polynomials
Nutrition
4a,b
Response to dietary lysine
Exponential equation
Model for economic
feeding levels
5
Optimizing dietary lysine
and energy level
Quadratic response surface
Model for economic
feeding levels
6
Optimizing protein and energy
levels in broiler feeds
Quadratic programming
7
Production responses to dietary
energy and protein
Multiple regression
IGM™ Growth Model
Environment
8
Operational characteristics; broilers
Many empirical
Mainly concerned with
energy transactions
9
Operational characteristics; turkeys
Many empirical
Mainly concerned with
energy transactions
Enterprise
10
Integrated production - decision
model for profit maximisation
Multiple regression
11
Profit maximisation
Multiple regression
Turkish industry data
a
References:
1
Low and Brookhouse (1967);
2
Hochman and Lee (1972);
3
Case
et al
. (2010); 4a Eits
et al
. (2005a); 4b Eits
et al
. (2005b);
5
De Beer (2009); Talpaz
et al
. (2013);
6
Pesti
et al
. (1986);
7
Harlow and Ivey (1994);
8
Teter
et al
. (1973);
9
Teter
et al
. (1976);
10
Costa
et al
. (2002);
11
Cevger and Yalçin (2003).
