Agriculture Reference
In-Depth Information
3.4
3.15
3.2
3.01
3.0
2.75
2.8
2.69 2.69 2.69 2.69
2.67
2.68 2.68
2.68
2.69 2.69
2.68
2.69
2.66
2.6
2.4
2.2
2.0
1985 1990 1996 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Year
Fig. 3.2.
Development in feed conversion rate (FCR) in Danish grower-finisher pigs, kg feed per kg gain
from 1985 to 2012. The initial body weight is 30 kg during all years, but the body weight at slaughter has
increased from 95 to 107 kg in 2012.
Table 3.1.
Alphabetical cla
ssification of amino acids according to their essentiality
Essential amino acids
Non-essential amino acids
Semi-essential amino acids
Histidine
Alanine
Arginine
Isoleucine
Asparagine
Cysteine
Leucine
Aspartic acid
Tyrosine
Lysine
Glutamic acid
Methionine
Glutamine
Phenylalanine
Glycine
Threonine
Proline
Tryptophan
Serine
Valine
phenylalanine (both containing an aromatic
group). The primary limiting amino acids are
lysine, methionine, threonine, tryptophan etc.,
but the order of limitation depends on the avail-
able feedstuffs used to compose the feed for the
animals. There may also be species-dependent
differences as poultry in general has a high
requirement for the sulfur-containing amino
acids for feather production.
In the gastrointestinal tract, the protein
fed to the animals is subjected to luminal diges-
tion releasing free amino acids and di- and tri-
peptides that are absorbed and transported into
the circulating blood (Lærke and Hedemann,
2012). The fed amounts of crude protein that
are digested are called digestible protein. The
protein digestibility depends on the composi-
tion of the feed and varies between species (and
categories) and among different ages. Often,
the protein digestibility is above 80% in pig
and poultry diets, but when large amounts of
e.g. fibrous feeds are included, the protein
digestibility is lower. In general, the amounts
that are not digested are excreted in faeces, and
those that are digested and absorbed may be
utilized for the synthesis of protein used for
many purposes including protein accretion in
the muscles or as a source of energy. If the
absorbed amino acids are not used for protein
synthesis, they are deaminated and the surplus
