Prof. José Luciano Andriguetto, technical director, and Guilherme Wolff, commercial technical manager at GFS, explain in a technical article published in O Presente Rural how to correctly calculate available and digestible phosphorus in feed formulation.
Phosphorus scarcity is a real risk for animal production
Phosphorus is one of the most important nutrients in animal nutrition and, at the same time, one of the most expensive in feed formulation. It is essential for bone development and energy metabolism, but its cost rises along with dependence on imported mineral sources, and waste from poor formulation weighs on both the producer’s wallet and the environmental impact of production.
For a long time, the criterion for including phosphorus in feed was simple and imprecise. As animal nutrition has advanced, that calculation has changed, and understanding the change today is what separates an efficient formulation from one that wastes money without the producer noticing.
From total phosphorus to digestible phosphorus
For a long time, formulating feed on total phosphorus (tP) alone was enough. The problem is that this value only tells you how much phosphorus is in the ingredient, not whether the animal can actually absorb it. Since much of the phosphorus in plant sources is bound to phytate, poultry and swine use little of it, because they do not naturally produce enough of the enzyme phytase to release it.
This led to including more inorganic phosphorus than necessary just to make sure the animal got enough. The concept then evolved into available phosphorus (aP), which considers the fraction of phosphorus that is free and can be absorbed in the digestive tract. More recently it advanced further, to digestible phosphorus (dP), the value that reflects what is actually absorbed in the animal’s intestine.
This evolution brought more precision to formulation, but also more complexity when interpreting the nutritional values of raw materials.
What virtual phosphorus is and why it calls for care
Two technologies changed how available phosphorus in feed is calculated: phytase and fatty acid polyol. Phytase releases the phosphorus and calcium bound to phytate in plant cells, making them available to the animal. Polyol, in turn, binds to free phosphate and calcium in the digestive tract, increasing the body’s absorption of these ions.
The key point is that neither technology creates new phosphorus in the feed. The phosphorus was already in the ingredient; these technologies only increase its availability and digestibility. That is why the phosphorus value assigned to phytase and polyol is called virtual phosphorus, a nutritional credit that must be calculated carefully.
When this credit is overestimated in the formulation, the risk is serious: it can compromise zootechnical performance, bone mineralization and eggshell quality. When the credit is calculated too conservatively, the producer misses part of the technology’s economic potential. The balance between these two extremes determines whether the formulation is truly optimized.
What this changes in practice for the producer
Formulating on digestible phosphorus instead of available phosphorus tends to deliver more consistent economic results and lowers the risk of a real phosphorus deficiency in diets that look right on paper but do not supply enough for the animal’s metabolism. With the cost of mineral phosphorus sources rising, this extra precision translates directly into production efficiency and sustainability.
About the article
The full article covering these concepts was written by Prof. José Luciano Andriguetto, technical director, and Guilherme Wolff, commercial technical manager at GFS, and published in the July 2026 issue of O Presente Rural.
