Optimizing Phytase in Animal Feed: Performance Starts With Knowing Your Limestone

Phytase in animal feed plays a critical role in unlocking nutrients and improving feed efficiency. But real-world results aren’t always consistent. Even when formulations look similar on paper, ingredient variability, especially from mineral sources, can strongly infuence performance. 

One often-overlooked factor? Limestone. 

When you use Axtra® PHY GOLD phytase, you’re already taking a step toward improving nutrient utilization and feed efficiency. An enabler to achieve this is the quality of the limestone used in animal feed. Understanding limestone quality and solubility is essential to unlocking the full potential of phytase. 

As a primary calcium source, limestone does more than contribute nutrients. It influences how those nutrients behave during digestion. Variability in limestone solubility and composition can directly affect how phytase performs, particularly in the upper digestive tract where early enzyme activity is most important. 

That’s why understanding your limestone isn’t just a formulation detail. It’s a practical step toward more predictable performance. This is where IFF’s limestone analysis service can help you better characterize your limestone and support more consistent, data-driven formulation decisions.  

Why Phytase in Animal Feed Effectiveness Relies on Limestone

Limestone is the primary source of calcium used in animal feeds, mainly due to its high calcium content and low cost. It is vital for bone development, metabolic functions, and overall animal performance. But not all limestone behaves the same once it enters the animal’s digestive system—and that difference can have a real impact on how well nutrients are absorbed and how effectively Axtra® PHY GOLD phytase performs in animal feed. 

Beyond calcium concentration alone, the critical differentiator is solubility: how quickly calcium is released during digestion. Some limestones dissolve very quickly, while others release calcium more gradually. When calcium is released too early or too late, it can interfere with phosphorus availability and reduce the effectiveness of phytase enzymes like Axtra® PHY GOLD. Even a high-quality phytase may not perform at its best if the limestone isn’t well matched to the formulation. 

This variability is often underestimated, but it can have a measurable impact on nutrient availability and overall formulation outcomes. 

Global Research Shows Wide Variation in Limestone Calcium Content

Large-scale research confirms that limestone variability is substantial. A global study that evaluated 641 limestone samples from 40 countries showed wide differences in limestone composition and behavior:

• Calcium content: Many samples deviated from the commonly assumed calcium content given in feed composition[AP2]  tables, affecting formulation accuracy
• Particle size: With limestones classed as “‘fine” ranging from ~40 to ~990 µm and those classed as ‘coarse’ ranging from ~300 to ~3000 µm
• Solubility: Among “fine” limestones, particle size explained only 52% of the differences in solubility, and for “coarse” limestones, there was no meaningful correlation at all.

These findings demonstrate that limestone sources differ widely in both composition and behavior, even when they appear similar. Relying on broad limestone classifications can lead to inaccuracies in nutrient availability, underscoring the need for precise, data-driven limestone characterization. Similar challenges are discussed in broader work on the practical application of enzyme matrix values across feeds with varying ingredient characteristics.

Why Limestone Variability Matters for Axtra® PHY GOLD

This variability is particularly important when using phytase in animal feed, including solutions like Axtra® PHY GOLD, which is engineered to rapidly break down phytate in the upper gut. By efficiently degrading phytate, Axtra® PHY GOLD releases phosphorus, calcium, energy, and amino acids for improved animal growth and feed efficiency.  

For enzymes designed to act quickly, these interactions are especially relevant in the early stages of digestion. 

To deliver consistent performance across diets, the matrix for Axtra® PHY GOLD has been carefully developed using extensive trial data, including the effect of limestone solubility on phytase. Rather than assuming uniform mineral behavior, matrix values are tailored to the limestone used, with phosphorus and calcium release calculated based on how the limestone dissolves in the diet, supporting accurate formulation and optimal performance. This type of approach reflects IFF’s research focus on refining phytase matrix values to better account for ingredient variability, as outlined in research on precise phytase matrix development. 

Turning Limestone Data Into Practical Formulation Insight

IFF’s Limestone Analysis Service supports more informed formulation decisions by providing a detailed characterization of the limestone used in feed. The service helps nutritionists clearly understand the limestone they are working with by measuring: 

• Particle size distribution 

• Calcium content 

• How quickly the limestone dissolves 

• Mineral composition 

Having access to this level of detail allows nutritionists to move beyond assumptions and work with actual ingredient data, supporting more precise and consistent formulation decisions. 

These results can be used in IFF’s Optimize Feed™ formulation tool to generate phytase matrix values and identify the optimal Axtra® PHY GOLD dose for your specific limestone.  By working with accurate ingredient data, nutritionists can support better nutritional values, improved animal performance, and greater feed cost savings. 

Limestone Knowledge as a Foundation for Feed Performance

Knowing your limestone plays a key role in effective feed formulation. By understanding its solubility and quality, nutritionists can unlock the full potential of Axtra® PHY GOLD, ensuring optimal nutrient release, animal performance, and sustainability goals.  

Feed efficiency remains a key priority across animal nutrition systems, and even small improvements in nutrient utilization can have a meaningful impact at scale. Phytase in animal feed already plays an important role in improving phosphorus availability, but its effectiveness depends on how well the diet supports its activity. 

IFF’s limestone analysis service empowers you with the data needed to make informed, science-led decisions.

Common Questions About Phytase in Animal Feed