Agriculture Reference
In-Depth Information
lipid turnover (Rivera-Torres
et al
., 2011) as
descriptors of growth. In egg layers the weight
of egg output is normally used, although
separate prediction of yolk, albumen and
shell weight is possible (Johnston and Gous,
2006). The growth of feathers in particular
is a difficult problem and one that remains
significantly unresolved (see discussion in
Gous
et al
., 1999).
Studies on nutrient utilization have
used a variety of techniques but still remain
rather inconclusive especially in growing
birds. Work concerning energy and protein
in laying hens has been reviewed by Chwal-
ibog and Baldwin (1995), and that concern-
ing amino acids by Fisher (1994). A series of
experiments from the laboratory of the late
Professor D.H. Baker provide the best direct
experimental evidence about the utilization
of amino acids in growing chickens (Baker
et al
., 1996; Edwards
et al
., 1997; Edwards
and Baker, 1999; Edwards
et al
., 1999). In-
formation on the utilization of amino acids
for maintenance is very inconclusive and
this is an area that may need a better the-
oretical and experimental basis. Mainten-
ance requirements have variously been
scaled to body weight (Fisher, 1994), to
metabolic body weight (Hurwitz
et al
.,
1978; King, 2001 and many others) and to
feather-free body protein weight scaled to
mature body protein (Emmans and Fisher,
1986). A paper by Nonis and Gous (2008)
concerned with lysine and threonine in
broiler breeder hens illustrates these various
points and also presents what is probably
the best experimental approach available at
this time.
The factorial approach to energy util-
ization has led to a huge literature in all
classes of stock. Again, earlier work was re-
viewed by Chwalibog and Baldwin (1995).
More recently an extensive series of papers
have been published covering broilers,
layers and broiler breeders (see Sakomura,
2004 for a summary of this work).
'Meeting these minimum needs will be
materially influenced by food consump-
tion'. In this final statement Heuser recog-
nizes one of the great challenges for nutri-
tional research and one that has not been
fully solved today. The ability to predict
food intake is an essential feature of nutri-
tional models and one for which a lot more
development is required.
For growing monogastric animals a
major stimulation to model development
was the pioneering work of Whittemore and
Fawcett (1974). Their description of the
simulation of protein and lipid deposition
in the growing pig (Whittemore and Fawcett,
1976) was really the start of modern devel-
opments in this field.
Table 1.2
lists the
models of poultry production systems that
have reflected, in a general way, the idioms
and, in particular, the levels of analysis
Table 1.2.
Mechanistic poultry production models.
Ref
a
System modelled
Notes
1
Broiler/turkey growth
Basis of EFG Software (1995) models
2
Broiler growth
With corrections for light:dark cycles
3
Rearing pullets
With corrections for seasonal light effects
4
Broiler growth
Not reviewed here
5
Broiler growth and production
SONCHES simulation system for growth and production of whole birds
6
Broiler growth
Full description of model in unpublished thesis. Not reviewed here
7
Broiler growth
8
Broiler growth
Native Taiwan breeds and feed optimization
9
Broiler growth
10
Broiler growth
French breeds and production systems
11
Turkey growth
12
Broiler breeder hens
See Gous, Chapter
3,
this volume
a
References:
1
Emmans (1981);
2
Isariyodom
et al
. (1988);
3
Muramatsu
et al
. (1989);
4
Burlacu
et al
. (1990);
5
Grosskopf
and Matthäus (1990);
6
Dänicke (1995);
7
Novák (1996);
8
Roan and Wang (1996);
9
King (2001);
10
Quentin (2004);
11
Rivera-Torres
et al.
(2011);
12
Gous and Nonis (2010).
