Agriculture Reference
In-Depth Information
production of 1 kg of meat or eggs defined as the
feed conversion ratio (FCR). The second topic
covers the amounts of nutrients and energy fed
to the animal in relation to the feed, and the
digestibility and availability of the nutrients.
their own programmes modified to local con-
ditions or established preconditions, but the
fundamental principles are largely the same
(e.g. NRC, 1994, 1998, 2012; Pig Research
Centre, 2012). Increasingly these feed opti-
mizing programmes also include 'a green
module' where the output of nutrients and
emissions is estimated enabling the user to
include an environmental aspect in his feed
optimization. Different models and equations
have been widely used to quantify the nutrient
excretion and efficiency for a couple of decades
(e.g. Dourmad
et al
., 1992; van der Peet-
Schwering
et al
., 1999; Poulsen
et al
., 2006;
Kebreab
et al
., 2008).
Feeding and Feedstuffs in
Monogastric Animals
Monogastric animals are normally fed cereal-
based diets supplemented with vegetable protein
sources such as soybean meal, canola and other
de-oiled by-products. In the past, it was the norm
to include feedstuffs of animal origin, but due to
restrictions and costs, the use of these feedstuffs
is often limited, but may depend on regional con-
cern and restrictions. The diets are typically sup-
plemented with minerals and vitamins and
other feed additives.
The digestive processes taking place are
basically the same in pigs and poultry. They
are true omnivores, but under farm condi-
tions, a large proportion of the feed is of plant
origin. The digestive processes mainly take
place in the upper part of the gastrointestinal
tract, but fibrous materials are partly fer-
mented and utilized in the large intestine. The
small intestine is the main site for absorption
of nutrients, but some nutrients and fluids are
also absorbed in the large intestine (Lærke and
Hedemann, 2012).
The animals must be provided sufficient
amounts of feed to ensure health and produc-
tion. Compound feed is composed of different
feedstuffs and supplements by use of feeding
programmes enabling the industry to formu-
late feed that contains sufficient amounts of
energy and nutrients to sustain the animals'
performance and health and the quality of the
end-products, meat or eggs. Computerized pro-
grammes for diet optimization are often based
on mathematical models that estimate the suf-
ficient amounts of energy, amino acids and
usually also certain minerals such as phos-
phorus (P) and calcium. These amounts are
adapted to the requirement set by the different
species at specific body weights or level of per-
formance. The models are continuously refined
and updated along with the development of
new knowledge and practical experience.
Individual countries (or regions) often have
Conversion of Feed into
Edible Products
The feed supply should cover the animal's physi-
ological need for nutrients and energy for pro-
duction and for the maintenance processes in
the body. Maintenance requirements cover the
amounts that are needed to keep up the basic
functions of the organs and body tissues and
comprise mainly energy and protein but occa-
sionally also some minerals. Generally, mainte-
nance requirements are given first priority by
the animal and growth and production are the
second priority.
The animal's physiological need for energy
and nutrients has to be met by intake of suffi-
cient amounts of feed, but the intake should be
tailored to fulfil the animal's minimum require-
ment to avoid excessive supply and unnecessary
excretion of nutrients. Feed intake is regulated
by complex processes that involve both meta-
bolic and physical mechanisms. These mecha-
nisms comprise a short-term process related to
the fed meal and a more long-term regulation.
Growing animals mainly rely on the short-term
regulation, whereas the long-term regulation is
more related to reproducing adult animals. This
complex regulation of feed intake has recently
been reviewed by Torrallardona and Roura (2009).
Part of the feed consumed is used for main-
tenance and concerns both energy and essen-
tials nutrients. The thermal environment in
which the animal is kept influences the feed
intake, and animals kept in cold environments
consume more feed as they need more energy for
