One focus in the development of OptiPhos® Plus was intrinsic thermostability. The aim was a granular product stable throughout the pelleting process at temperatures up to 85^{o}C, without any compromise in the performance of the phytase.

During the development and selection stages, it was often noticed that phytases with higher heat stability had lower performance in feed. The main reason for that is visualised in Figure 1.

- Each phytase has a temperature profile and an optimum temperature where it will perform at its maximum.
- The higher this optimum temperature, the more heat stable the phytase will be. For instance, Phytase 2 in Figure 1 is more heat stable than Phytase 1.
- However, the body temperature of an animal is approximately 40
^{o}C, so a higher optimum temperature also means a lower activity at 40^{o}C, requiring a higher dose per kg of feed. For example, Phytase 2 (the more thermostable phytase) needs to be included at a higher dose to equal the performance of Phytase 1 at 40^{o}C (Figure 1).

Figure 1. A phytase with a high optimum temperature needs higher dosing at animal body temperature (40*°*C, blue dashed line) compared to a phytase with a lower optimum temperature

Increased heat stability combined with improved animal performance was not simple, but we achieved this with OptiPhos® Plus, showing improved matrix values versus current OptiPhos®.

**Higher matrix values for OptiPhos® Plus**

Biochemical work carried out during the development of OptiPhos® Plus has revealed that OptiPhos® and OptiPhos® Plus have a similar V_{max} value (maximum speed of phytate degradation). However, it was observed that OptiPhos® Plus had a higher affinity to phytate compared to OptiPhos® (Figure 2).

The affinity of a phytase is defined as the K_{m} value, which is the phytate concentration at which the speed of the phytase is 50% of its V_{max} (Figure 2). A low K_{m} (high affinity) means that the phytase can keep up its maximal speed for a longer time, even when phytate concentrations are getting low, and so will give higher phosphorus (P) matrix values *in vivo*.

Figure 2. Michaelis Menten Kinetic studies on OptiPhos® and OptiPhos® Plus

**Validated in animal trials**

Many animal studies in broilers and pigs have been conducted to confirm the P matrix value for OptiPhos® Plus at different inclusion levels. The P release response with increasing dose is a logarithmic curve as shown in Figure 3 for broilers and turkeys (available P (aP)) and in Figure 4 for pigs (digestible P (Dig. P)).

Figure 3. Available P matrix values of OptiPhos® Plus versus OptiPhos® in broilers and turkeys

Figure 4. Digestible P matrix values of OptiPhos® Plus versus OptiPhos® in pigs

**Scientifically claimed matrix values**

Unlike many of our competitors, the P matrix values for OptiPhos® Plus have been calculated based on all our research data and not just the best trials. This means that the values we state are scientifically supported, reliable, and do not represent an overestimation of the potency of OptiPhos® Plus. Even formulating with low aP or Dig. P targets in the diets, OptiPhos® Plus will deliver correct values. This gives the nutritionist 100% certainty that when calculating with these values, no P deficiency will be observed in the field under any circumstances.

**Conclusion**

The improved intrinsic heat stability of OptiPhos® Plus does not compromise its performance capabilities. On the contrary, its higher affinity to phytate leads to a higher phytate degradation and by consequence to higher P matrix values.

The matrix values of OptiPhos® Plus are scientifically supported, using all trial data, reliably and consistently delivering P release and optimal animal performance.