Agriculture Reference
In-Depth Information
It is anticipated that the need for supple-
mentation of feed phosphate will decrease over
the next few decades along with the improve-
ments in specific knowledge on the animals' P
requirements (especially the reproducing animals)
and upgraded experience and understanding of
the use of microbial phytase. However, it is still
forecast that globally there will be a need for
feed phosphate supplementation in some cases,
although the demand is anticipated to be greatly
reduced. It is expected that very young animals
and animals with a very low FCR may need extra
P depending on the feedstuffs used. There are
many different feed phosphates available on the
market, but the P digestibility depends on the ori-
gin of the mined phosphate, the production prin-
ciples, chemical composition etc. Many studies
have found that the true P digestibility is around
80% in the water-soluble sources such as mono-
sodium phosphate and phosphoric acid, about
54% in di-calcium phosphates and about 67%
in mono-calcium phosphates (Poulsen, 2007).
Higher values (up to 98%) are given in other
studies but these values are expressed in apparent
P digestibility (Dellaert et al ., 1990). The fact is
that whenever feed phosphate supplementation is
needed, feed phosphates with high P digestibility
and low contents of undesired heavy metals such
as cadmium, lead etc. should be preferred.
In conclusion, monogastric animals should
be fed sufficient amounts of available P to cover
the need to sustain maintenance and production
to ensure health and growth/reproduction in a
sustainable balance between welfare, produc-
tion and environmental load. However, deficient
but also excessive P supplies may have negative
effects on bone mineralization and health
(Sørensen et al ., 2012) as well as eggshell strength
(Hammershøj, 2012, unpublished results).
fat. Furthermore, Zn also plays a role in cell repli-
cation and in the immune function. The physio-
logical requirement for these minerals is not
fully understood although most official tables on
nutrient requirement specify values for most spe-
cies and categories. However, these recommen-
dations are given in total amounts per kg feed,
because the knowledge on digestibility so far is
too limited to be able to express the requirement
in digestible amounts per kg feed. This was also
the case for P until 20 years ago where the rec-
ommendations gradually shifted from total
amounts of P to digestible amounts of P or
amounts of non-phytate P in poultry (e.g. NRC,
1994, 2012; Pig Research Centre, 2012).
Copper has been widely used as growth pro-
moter in pig production although the mode of
action has not yet been fully understood. However,
due to environmental concern, the use of Cu as
growth promoter has attracted much attention
and in some areas (e.g. within the EC), and the use
of Cu as growth promoter has now been restricted
and limited to be used in very young pigs after
weaning (until 12 weeks of age). Zinc fed in excess
amounts is known to induce moult in hens,
but no reports on environmental concerns have
been given so far. Zinc (as ZnO) has been widely
included in high concentrations in feed for wean-
ing pigs for about 25 years after a report showed
positive effects of ZnO being able to prevent and
cure post-weaning diarrhoea (Poulsen, 1989). It
was shown that this high concentration of ZnO
had to be given for 2 weeks until the pigs' feed
intake was normalized. However, the use of
high concentrations of ZnO was not restricted to
2 weeks post-weaning in many occasions. This
has attracted environmental concern in livestock-
dense areas due to high amounts of Zn accumu-
lation in soils amended with manure from pigs
fed Zn-fortified feed (Jondreville et al ., 2003).
Different scenarios show that it may only take
50-200 years to reach a critical concentration of
Zn and Cu in soils amended with pig manure in
intensive pig-producing areas (Poulsen, 1998).
Zinc and Copper Efficiency
Zinc (Zn) and copper (Cu) are essential trace ele-
ments, and at the same time they belong to the
class of heavy metals. All monogastric animals
require Zn and Cu, which normally are provided
by the feed. Copper is required for the synthesis of
haemoglobin and is part of many oxidative
enzymes that ensure proper metabolic processes
in the body. Zinc is part of many enzymes involved
in the metabolism of carbohydrates, protein and
Methane Emissions
Over the last decades, the emission of greenhouse
gases (GHG) has attracted much concern due to
climate change concerns. Methane is produced
during enteric fermentation and represents a
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