What is the function of phosphorus in the animal?

Phosphorus has more physiological functions than any other mineral, such as:

Development and maintenance of skeletal tissue, the greatest proportion of phosphorus is devoted to maintaining and supporting the skeleton, where it is c-precipitated with calcium in the form of hydroxyapatite. The skeleton not only acts as a support system but also as a reservoir of phosphorus and calcium from which the body can draw.

Maintenance of osmotic pressure and acid-base balance

Energy utilization and transfer; phosphorus plays a vital role in energy regulation

Appetite control and efficiency of feed utilization

And many more/ …

Are phosphorus requirements of the different animals known?

Yes, from all animals phosphorus requirements are tabled. However, the system of expressing these requirements differs between the different areas. In Europe for pigs the requirements are expressed in digestible phosphorus, for poultry in available of absorbable phosphorus and for ruminants just the total amount of phosphorus.

Is the content of digestible phosphorus of the different inorganic feed phosphates known?

Yes, in the past but even now trials are carried out to assess the level of digestible phosphorus in the different feed phosphates as accurate as possible. Tabled values do exist and based on this, feed formulators and feed producers can produce feed that match the animal phosphorus requirements as accurate as possible.

Are feed phosphates the only phosphorus sources?

No the majority of phosphorus in animal feed is originating from plant materials. However, this is largely in the form of phytate phosphorus which is virtually unavailable for monogastric animals (poultry, pigs) making it impossible to meet the animal requirements with plant materials alone. Additional phosphorus supplementation is essential. Ruminants have the ability to digest the phytate phosphorus in plant materials in the rumen. But even so, comparison with the requirements of ruminants with levels of phosphorus supplied by normal pasture show that in most cases additional phosphorus in the form of inorganic feed phosphates is necessary.

Are there alternatives to feed phosphates?

Indeed; All feed materials containing high total and available phosphorus levels can be used as a source of phosphorus in animal nutrition. Nowadays, there is also the possibility to use phytase, an enzyme capable to liberate the phytate-bound phosphorus in plant materials and making the phosphorus available for monogastric animals. However, phytase is not capable to release all phosphorus and, therefore, there is still a need for supplementing animal feeds with inorganic feed phosphates.

What happens with the phosphorus which is not digested by the animal?

This is voided in the manure, where it can be used as a cheap natural source of phosphorus next to nitrogen and other minerals. The majority of the phosphorus in the manure however, originates not from the use of inorganic feed phosphates but originates  for the greater part (>95%) from undigested plant phosphorus.