Feed phosphates
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Inorganic feed phosphates (IFP) are inorganic salts of phosphoric acid. Inorganic feed phosphates are used to meet the phosphorus requirements for animal production: to ensure optimal growth, fertility and bone development.[1][2]
The importance of phosphate (PO3−4) is reflected in the number of metabolic processes in which phosphorus takes part. By far the greatest amount of phosphorus is used to maintain and support the skeleton. About 80% of an animal's phosphorus is located here, co-precipitated with calcium (Ca) in the form of hydroxyapatite complex (Ca10(PO4)·6(OH)2), where it acts not only as a support system but also as a reservoir of phosphorus. In the soft tissues, phosphorus is a major component of the cells, membranes and body fluids. It also plays an important role in the energy supply. In addition phosphorus acts as a buffer, is involved in phospholipids and fatty acids transfer and in the formation of amino acids as well as DNA and RNA. Therefore, phosphorus is indispensable for animals.
Production of IFPs
Phosphates occur widely in nature mostly as phosphate rock or fluorapatite. There are large deposits in Russia, USA, North Africa, and China, where they are obtained mostly by open cast mining. Over 85% is used in fertiliser production, and only less than 7% in feed phosphate production. Two types of deposits exist: of volcanic and of sedimentary origin.
These crude phosphates cannot be used by animals directly, but must be converted into a form which can be digested by the animal. In addition, the undesired impurities must be removed or lowered to an acceptable level. The starting point of industrial feed phosphate production is technically pure (ortho-) phosphoric acid (H3PO4), which is obtained from the apatite in a wet chemical process.
| Example of phosphoric acid production
Wet-process phosphoric acid is prepared by adding sulfuric acid (H2SO4) to apatite or tricalcium phosphate rock resulting in the following reaction:
Wet-process acid has to be purified by removing fluorine and other undesirable elements to produce feed-grade phosphoric acid. |
Different types of inorganic feed phosphates
Depending on the process and on other mineral sources used, different types of inorganic feed phosphates can be produced. The majority of the inorganic feed phosphates used in the EU and worldwide are calcium phosphates in different forms (mono-, di- and monodi-calcium phosphates) but also magnesium phosphates, sodium phosphates and even ammonium phosphates are used in animal nutrition. The end-product quality depends on the treatment and production process. Due to different chemical compositions of the different feed phosphate sources, large differences do exist in their phosphorus availability for the different animal species. However phosphate from the same source, produced by the same process, using the same raw materials, shows consistent phosphorus availability, which can be measured in biological assays.
| Example of a calcium feed phosphate production
Phosphoric acid is neutralized by means of calcium oxide or calcium carbonate, or a mixture of them.
Or, based on dicalcium phosphate
Depending on the used qualities[clarification needed] the resulting products are more or less pure di- or monocalcium phosphates. |
Quality
Consistent phosphorus availability relies on strict quality control during the process, to avoid degradation of orthophosphate into other unavailable phosphate forms. Impurities which are naturally occurring in the used raw materials must also be considered. But also feed hygiene and good manufacturing practices should be complied with at all stages.