Agriculture Reference
In-Depth Information
Fig. 2.1.
Screenshot of InraPorc illustrating the response of the pig to the energy supply at 75 days of age.
The solid dots indicate the protein and lipid deposition at this age. The protein and lipid deposition
response curves are also given as well as the marginal response to a change in energy intake at 75 days
of age.
increases and there will be a point in time
where protein deposition is no longer deter-
mined by feed intake capacity but by PD-
max. In InraPorc, we assume that at 70 kg of
body weight, the feed intake capacity of the
pig is sufficient to attain PDmax (as indi-
cated by the parameter '
BW PDmax
'), but
this value can be modified by the user. The con-
cepts depicted in
Fig. 2.1
are mostly important
in situations where feed restrictions are im-
posed. For body weights before '
BW PDmax
',
there may be an interest in maximizing feed
intake because a feed restriction would ad-
versely affect both protein and lipid deposition.
For body weights greater than '
BW PDmax
',
a (small) feed restriction only adversely affects
lipid deposition, resulting in leaner animals.
This feeding strategy is often applied in
France (with liquid feeding systems) to con-
trol carcass fatness during the finisher phase.
It is important to mention that InraPorc
only predicts the response to farmer-imposed
feed restrictions. Acute changes in feed in-
take (e.g. due to a sanitary challenge or to
heat or cold stress) are not accounted for
and these changes may affect protein depos-
ition differently from a farmer-imposed feed
restriction. For example, Le Bellego
et al
.
(2002) showed that a heat-induced feed re-
striction affected protein and lipid depos-
ition differently from an experimentally in-
duced feed restriction.
Response to the Amino Acid Supply
In InraPorc, the response to the amino acid
supply is modelled in a rather classical way
by separating the basal endogenous losses,
the maintenance requirement (due to losses
of integuments and minimum protein turn-
over), the amino acid composition of whole-
body protein and the maximum efficiency
with which available amino acids can be
The supply of digestible amino acids can
be expressed on an apparent ileal digestible
(AID) or on a standardized ileal digestible
(SID) basis. The difference between both
modes of expression is the way the basal
