That’s a good question, but perhaps the better question is “why don’t exogenous enzymes work in pigs the way they do in broilers?” For years, exogenous enzymes have been a cornerstone of broiler nutrition. Enzymes work in broilers, they are predictable and repeatable. Some might argue that you cannot feed broilers without enzymes! Swine nutritionists, on the other hand, have struggled to gain predictable and repeatable performance from exogenous enzymes in pigs; sometimes they work, sometimes they don’t. Phytase appears to be the only exogenous enzyme that performs up to expectation consistently in swine.