E. Kiarie, Y. Rho, and C. Zhu
Department of Animal Biosciences
University of Guelph, Guelph, ON, Canada
Feed enzymes are the most researched and used additives in monogastric nutrition. The rationale for developing and applying feed enzymes is largely based on the premise that pigs have biological limit for digesting most of the nutrients in common feedstuffs. The undigested nutrients are excreted in the manure with negative implications on production efficiency, profitability, and sustainability of swine operations. The peculiarity is that feedstuffs contain anti-nutritional factors (ANF) such as phytic acid or fractions that are not degraded sufficiently or indeed at all by the conditions and the array of digestive enzymes in the gastrointestinal tract. Supplemental phytase is almost ubiquitous in swine diets, and the economic and environmental consequences are well documented. Carbohydrases and proteases often show improvement on digestibility but exhibit inconsistent responses in growth performance. However, feed ingredients are exceedingly structurally complex, and the use of defined blend of enzymes displaying a range of activities holds tremendous opportunity for extending benefits to gut health and function. In this context, there is increasing evidence feed enzymes can impact gut microbial ecology by reducing undigested substrates and producing oligosaccharides in situ from complex dietary carbohydrates with potential prebiotic effects. The ability to find and evolve the next generation of feed enzymes will be driven by, among other factors, understanding the mechanisms of action and the implications on animal health and performance. Furthermore, most feed enzymes evaluation and interpretation takes a simplistic view, whereas pigs often receive diets containing a mix of distinct additives. It is imperative to consider evaluating combinations of additives to document animal responses and potential synergies. The present review is an attempt to summarize current thoughts in feed enzymes application in swine nutrition with specific emphasis on non-phytase enzymes. The scope will underscore mechanisms and suggest opportunities for expanded exploitation of feed enzyme biotechnology in modern swine feeding programs.
Keywords: feed enzymes, swine nutrition, carbohydrases, protease, digestibility, gut health, growth performance