Inorganic Feed Phosphates explained

Phosphate Quality?

Most raw materials of plant and animal origin, used in animal nutrition, contain phosphorous.? Nutritionists rely on both organic and inorganic feed phosphates (IFP) to supply the correct amount of digestible phosphorus in animal diets.?

Introduction?

Phosphorus (P) is an essential mineral. It plays a key role in cellular metabolism, including storage and transport of energy e.g. ATP production, in cellular regulatory mechanisms, and in bone mineralisation. In mammals, approximately 75% of the body’s total phosphorus is stored in bone, whereas in broilers this is only 55%, with the remaining phosphorus being retained in soft?

tissues, including muscle and organs (Van Krimpen et al., 2013). Its function in the animal’s metabolism is critical and adequate P supply is required to enable the animals to utilise their genetic?potential for growth, feed efficiency and skeletal development.?

Phosphorus inclusion in poultry diets deserves adequate attention because of the physiological?requirements, limited phosphate reserves in the world, the cost of the diet and the excretion into the environment.??

In general, phosphorus is the third most expensive nutrient in the feed, after energy (ME) and protein or amino acids.? For this reason, it is important to optimize the available phosphorus content in the diet as much as possible to reduce the feed cost, in addition to reducing phosphorus excretion into the environment.??

?Inorganic Feed Phosphates?

Since the phosphorous supply from organic sources is low, variable and often not digestible by animals, nutritionists rely on inorganic feed phosphates (IFP) to supplement animals with phosphorous.?

Today many different inorganic feed phosphates are used as dietary P-supplements.? It should however be stressed that not all inorganic P sources are the same in terms of quality.?

The quality of inorganic P can differ greatly in properties such as chemical composition, physical appearance, undesirable element content and very importantly, digestibility of P.? It is therefore vital to have a sound knowledge of the differences between the products to make a well-informed choice to prevent an over or under-supply of phosphorous to the animals.?

?Inorganic Feed Phosphate sources?

Inorganic Feed Phosphates (IPFs) used in animal nutrition include Mono Calcium phosphate (MCP), Mono Dicalcium Phosphate (MDCP) as well as Dicalcium Phosphate (DCP) – there is also Tricalcium Phosphate (TCP) which should not be used in animal feeds due to its low P digestibility.???

It is important to understand that IFPs are not pure products. Within any IPF there is a fraction of MCP, DCP and TCP present. It is the concentration of a fraction of each of these products within the IPF that lends it its name.??

?Naming of Inorganic Feed Phosphates?

Before we can discuss the quality of an IFP it is important to understand the naming of a product.? When a phosphate product is produced, 3 chemical forms of phosphates can be produced, namely MCP, DCP and TCP. ??

The production process of the 2 main compounds of an Inorganic Feed Phosphate is as follows:?

?2H3PO4 + CaCO3 --> Ca(H2PO4)2·H2O. + CO2?

phosphoric calcium monocalcium phosphate carbon?

acid carbonate monohydrate dioxide?

and?

H3PO4 + CaCO3 + H2O --> CaHPO4 . H2O + CO2?

phosphoric calcium water dicalcium phosphate carbon?

acid carbonate dihydrate dioxide?

The above two processes happen simultaneously, so during the production process of either MCP, MDCP or DCP, there will always be a mixture of all the forms of phosphate in a product, eg. If you produce a MCP there will always be a little DCP in the product and if you produce a DCP there will always be a little MCP in the product. So, the IFP produced, will obtain its name from the dominant form of the phosphate. ?

For a product to be called a MCP, 80 % of the P in the product must come from MCP, for a DCP, 50 % or more of the phosphate in the product must come from DCP and to be called a MDCP, between 50 and 79 % of the P in the product must come from MCP.??

You can also produce MDCP with different ratios of MCP : DCP.? The amounts of the DCP in MCP or MCP in DCP or MCP:DCP in MDCP, will depend on the quality of the acid used as well as the control over the production process. TCP is formed if a manufacturer does not have control over the production process.??

These commercial inorganic feed phosphate sources are therefore not pure MCP or DCP or TCP, but chemical mixtures of MCP, DCP and TCP.? Most people refer to IFP as either MCP or DCP, but, depending on the ratio of MCP to DCP in a specific product, you will have either an MCP, DCP or MDCP.?

?Quality of Inorganic Feed Phosphates??

Remember that MDCP is not a physical mix between MCP and DCP, but a chemical mix of MCP and DCP.??

Phosphate in the MCP form is the most digestible by animals, followed by DCP dehydrate, then DCP an-hydrate and then TCP, which has very low digestibility in animals.??

Digestibility - According to numerous trials done with chickens and pigs over the years, it was established that phosphate in the MCP form is more available for use by animals than phosphate in the DCP form – where DCP in the hydrate form (CaHPO4 . H2O) is also more digestible than DCP in the anhydrate form (CaHPO4).?

Trials have also shown that there is a significant difference between the digestibility of P from various MDCP sources, mainly because of the MCP :DCP ratio of different MDCP sources and the hydrate or anhydrate form of the DCP.? The more MCP in a MDCP the higher the digestibility will be with the same being true if more DCP is in the hydrate form.???

Recent ileal digestibility trials done by Yara Animal Nutrition on poultry had the following results for our Kynofos 21, a MDCP product:?

Table 1 Ileal Digestibility of different IFP Sources?

Treatment? P (%)?

MDCP mix? 70.7b?

Kynofos 21?? 80.2a?

Competitor MDCP? 70.6b?

MCP? 79.4a?

P-Value? 0.009?

SEM? 2.34?

Chemical Composition – Inorganic Feed phosphates not only need to be highly digestible, but it also needs to consistently comply with certain specifications.? A MCP product contains 22.7 % P, a MDCP product contains 21 % P and a DCP product contains 18 % P.? Both MCP and MDCP products has a calcium content of between 15 and 18 % while a DCP product contains maximum 24 % calcium.???

Undesirable elements – Elements such as fluorine, cadmium, arsenic, lead and mercury, comes from the rock from which phosphoric acid is produced.? When IFP’s are produced, de-fluorinated phosphoric acid needs to be used to ensure that IFP’s are low in undesirable elements.?

Summary?

Phosphorus (P) is an essential mineral therefore the correct amount of digestible phosphorus must be included in animal diets. There is a significant difference between the digestibility of P from various MDCP sources. It is however important to understand the difference between the different Inorganic Feed Phosphates to be able to understand how the quality of the Phosphates will play a significant role in the production of the used to produce high-quality animal feed.?

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