Toward optimal value creation through the application of exogenous mono-component protease in the diets of non-ruminants

Exogenous protease has formed part of several commercial enzyme admixtures for the past 15-20 years but has become available as a mono-component enzyme only in the last 5-10 years (Cowieson and Adeola, 2005; Fru-Nji et al., 2011). As part of an enzyme admixture (often also containing various carbohydrases and/or phytase) it is difficult to separate the contributions of the component parts and the efficacy of each has implicit rather than explicit value. However, the effectiveness of mono-component enzymes can be readily assessed under different production and nutritional circumstances and their complementarity with alternative enzymes is readily rendered transparent. The motivation for the use of exogenous protease in non-ruminant nutrition is typically the reduction of feed cost at constant animal performance. This objective is usually achieved via displacement of expensive protein/amino acid sources in the diet through the assignment of a nutrient matrix on the enzyme in least cost formulation. Recently attention has moved from this classical approach to protease application to so-called 'extra-proteinaceous' effects including environmental benefits, litter management, enteric resilience, uniformity and microbial stability. Whilst these 'secondary' effects may not be the principal motivator for the use of proteases in animal production they are increasingly visible and require explanation. Furthermore, these responses, if understood, allow positive translation to production metrics such as reduced FCR and improved weight gain. It is the purpose of this review to briefly summarise the current state of the art in mono-component exogenous protease use in non-ruminants and to suggest mechanisms whereby the 'extra-proteinaceous' effects may be explained. Finally, key diet/animal factors that may promote beneficial effects of exogenous protease on live performance will be discussed.