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Phosphorus / phosphate sources
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1.
Functions
The formation and maintenance of the skeleton, bones and teeth
largely depends on phosphorus: 80 % of body‘s phosphorus
is located in the bones and teeth, co-precipitated with calcium
in the hydroxy-apatite complex. The remaining 20 % is contained
in nucleotides such as ATP, nucleic acids, in phospholipids
and other phosphorylated compounds.
The outstanding importance of phosphorus is therefore also reflected
in its metabolic functions: regeneration of energy supply, transfer
of fatty acid, formation of amino-acids, cell membrane bilayer
and acid-base buffer. Phosphorus is also important in fertility
and reproduction as well as in milk secretion, eggshell formation
and muscle tissue formation.
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2.
Main inorganic feed phosphates
Calcium phosphates are the most common sources:
dicalcium phosphate
(dihydrate, anhydrous)
monodicalcium
phosphate
monocalcium phosphates
For specific feed formulations are used:
magnesium phosphate
mono-sodium phosphate
mono-ammonium
phosphate
And combined phosphates:
calcium magnesium
phosphate
sodium calcium
magnesium phosphate
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3.
Quality parameters
3.1 Biological availability/digestibility
Depending on the chemical form, the chemical purity and the
production process it is demonstrated by “in vivo”
experiments (bone mineralisation) that the relative biological
availability (RBV) of feed phosphates produced by EMFEMA members
can vary between 80% and 100% (available phosphorus). Other
“in vivo” experiments determine the phosphorus absorbed
in the intestinal tract (digestible phosphorus) mainly for pigs.
“In vitro“ methods (solubility) are less accurate
but can give an approximation (soluble phosphorus in ammonium
citrate or in 2 % citric acid).
3.2 Purity
All feed phosphates (as single feed materials) used in the European
Union have to be conform to the Directives 2002/32/EC, 2003/57/EC
and 2003/100/EC on undesirable substances as follows:
| Fluorine |
max |
2.000
ppm |
| Cadmium |
max |
10
ppm |
| Arsenic |
max |
10
ppm |
| Lead |
max |
15 ppm |
| Mercury |
max |
0,1
ppm |
| Dioxins |
max |
1
ng/kg |
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4.General
criteria for selection of feed phosphates
Total phosphorus content
available/digestible phosphorus content
calcium/phosphorus ratio
solubility
pH
level of undesirable substances
physical form (powder / granulated)
density
use: premix - compound feed - supplements formulation according
to raw materials,
animal species
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5.
Analytical methods
| Total
phosphorus (according to Directive 77/535/EEC) |
quinoline
phosphomolybdate gravimetric |
| Soluble
phosphorus |
in
2 % citric acid :
in alkaline ammonium citrate (Petermann)
in water |
| Calcium |
atomic absorption spectrometry
X-ray fluorescence |
| Sodium |
atomic
absorption spectrometry
X-ray fluorescence |
| Magnesium |
spectra
photometric atomic absorption
X-ray fluorescence |
|
Fluorine |
ion- selective electrode |
| Cadmium |
atomic
absorption spectrometry |
| Arsenic
|
atomic
absorption spectrometry |
| Lead |
atomic
absorption spectrometry |
| Mercury |
atomic
absorption spectrometry |
| Moisture |
-dihydrate dicalcium phosphate |
acetone
wash method |
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-others |
oven
drying method |
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Grade of hydration |
X-ray
diffraction
thermo-gravimetric method |
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6.
Conversion factors
| P
x 2.291 = P2O5 |
Ca
x 1.39 = CaO |
Mg
x1.66 = MgO |
| P2O5
x 0.437 =P |
CaO
x 0.715 = Ca |
MgO
x 0.6 = Mg |
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