Agriculture Reference
In-Depth Information
a large extent when the pig is fed P in excess,
leaving the urine as the main route for elimina-
tion of excess P.
The excretion and utilization of P in poultry
depends on the type of the animal and produc-
tion objectives. Table 3.4 shows that P utilization
is the highest in the youngest broilers and
decreases in heavier birds. Laying hens have a
high P excretion and a low P utilization.
Interestingly, birds raised organically have a
higher P excretion compared with convention-
ally raised birds in Denmark. It is anticipated
that the P efficiency will be greatly improved
over the next few years due to increased focus on
P use in poultry production.
Despite the wide use of microbial phytase
supplementation in the feeding of monogastric
farm animals, the utilization of P is often quite
low and at the most about 60% in intensive
farming. The main reason is that most studies
on the improvements of P efficiency have been
conducted using dry feeding systems in poultry
and pigs. Studies with animals equipped with
cannulas in the stomach have shown that the
degradation of InsP
6
in dry fed pigs is not com-
pletely in the anterior part of the gastrointesti-
nal tract before the place where the absorption
of phosphate takes place. Approximately 60%
and 30% of the phytate intake is still intact
when the feed without or with microbial
phytase leaves the stomach (Blaabjerg
et al
.,
2011). Such studies emphasize that the time
needed for complete degradation of InsP
6
is
more than 5 h. As such, the idea of 'pre-digestion'
that takes place before the animal consumes
the feed has been introduced. This approach is
possible by use of liquid feeding where feed
and liquids are mixed prior to feeding allowing
sufficient time for the enzymatic degradation
of InsP
6
to take place (Lyberg
et al
., 2006;
Blaabjerg
et al
., 2010). Results have shown that
complete degradation of InsP
6
before feeding
may increase the P digestibility to about 70-75%
depending on which feedstuffs are included in
the feed (Blaabjerg
et al
., 2010; Poulsen, 2012,
unpublished results). However, the liquid
feeding conditions such as time, pH, enzyme
addition, temperature, mixing etc. have to be
outlined to ensure safe use of this approach
in practical farming.
Regardless of the worldwide use of phytase,
a lot of inorganic P is still used as supplement in
the feeding of monogastric animals. Obviously,
the use of phytase is not appropriate in all cases,
and it is anticipated that the use still has to be
optimized in many farm situations. Furthermore,
research on liquid feeding may create the basis for
further replacement of inorganic P. This is really
needed since the global P reserves are projected
to be very limited and may cause a pronounced
spike in P prices (Cordell
et al
., 2009). In Denmark,
the use of inorganic mineral P was calculated to
approximately 13,000 t (elementary P) in 2001
regarding the feeding of monogastric animals
(Poulsen and Rubæk, 2005). Since the introduc-
tion of a P tax in 2004, the use of feed phosphates
has been reduced 40-50%. Another approach
may be breeding for cereal or vegetable protein
crops where phytate constitutes a reduced part
of the total P content (Poulsen
et al
., 2001).
Table 3.4.
Phosphorus exc
retion and utilization in poultry (Poulsen
et al
., 2012).
Phosphorus utilization
(% of intake)
Type of poultry
Duration
Phosphorus excretion (kg)
1000 broilers
30 days
8.64
40
1000 broilers
32 days
9.71
40
1000 broilers
35 days
12.4
35
1000 broilers
40 days
16.2
34
1000 broilers
81 days, organic
41.1
15
100 female turkeys
a
112 days
12.7
36
100 geese
a
91 days
16.0
18
100 ducks
a
52 days
4.29
32
100 layers hens, batteries
1 year
15.6
21
100 laying hens, free living
1 year
17.1
19
100 laying hens, organic
1 year
22.6
15
a
The production of these birds are limited in Denmark and the calculated excretions are only indicative.
