How to value lucrative enzymes in linear programming

Enzymes have become a key solution in resource efficiency. Phytase is known to raise the available or digestible phosphorus. However, the power to release digestible P out of plant phytate is not linear. This means that it’s no use adding (expensive) phytase to the feed unlimitedly. But how to deal with this non-linear effect? How to obtain the most cost-effective use of enzymes in your formulation? In modern feed formulation the main question is: How can I easily formulate the cheapest c