Olayiwola Adeola (Purdue University, USA) and Aaron Cowieson (University of Sydney, Australia) recently reviewed the opportunities and challenges in using exogenous enzymes to improve non-ruminant animal production in the Journal of Animal Science.
This review is an attempt to summarize current thinking in this area, provide some clarity in nomenclature and mechanisms, and suggest opportunities for expanded exploitation of this unique biotechnology.
Diets fed to non-ruminant animals are composed mainly of feed ingredients of plant origin. A variety of anti-nutritional factors such as phytin, non-starch polysaccharides (NSP), and protease inhibitors may be present in these feed ingredients, which could limit nutrients that may be utilized by animals fed such diets.
The primary nutrient utilization-limiting effect of phytin arises from the binding of 6 phosphate groups, thus making the P unavailable to the animal.
The negative charges allow for formation of insoluble phytin-metal complexes with many divalent cations.
Furthermore, phytin and protein can form binary complexes through electrostatic links of its charged phosphate groups with either the free amino group on amino acids on proteins or via formation of ternary complexes of phytin, Ca2+, and protein.
The form and extent of de novo formation of binary and ternary complexes of phytin and protein are likely to be important variables that influence the effectiveness of nutrient hydrolysis in plant-based diets.
Non-starch polysaccharides reduce effective energy and nutrient utilization by non-ruminant animals because of a lack of the enzymes needed for breaking down the complex cell wall structure that encapsulate other nutrients.
Enzymes are used in non-ruminant animal production to promote growth and efficiency of nutrient utilization and reduce nutrient excretion. The enzymes used include those that target phytin and NSPs.
Phytase improves growth and enhances P utilization, but positive effects on other nutrients are not always observed.
NSP-hydrolyzing enzymes are less consistent in their effects on growth and nutrient utilization, although they show promise and it is imperative to closely match both types and amounts of NSPs with appropriate enzyme for beneficial effects.
When used together with phytase, NSP-hydrolyzing enzymes may increase the accessibility of phytase to phytin encapsulated in cell walls.
The future of enzymes in non-ruminant animal production is promising and will likely include an understanding of the role of enzyme supplementation in promoting health as well as how enzymes may modulate gene functions.