3rd International Poultry Meat Congress

the GI tract which are fermented in the caecum, triggering the ileal brake mechanism. This effect
has been recently demonstrated by measuring one of the hormones responsible for regulating the
ileal brake mechanism, peptide YY (PYY; Singh et al., 2012). It is evident that xylanase addition
can increase PYY concentration in the serum of broilers, possibly indicating a modifying effect
of xylanase on gastric residency. Further evidence for this mechanism is presented by Cowieson
& Bedford (2009) where xylanase effect on ileal amino acid digestibility was found to be a
constant fraction of the undigested amino acids in the diet. This generic effect suggests that
de-caging is not a major mechanism for xylanase or those amino acids most often found in the
aleurone layer of e.g. wheat (such as Arg) would be disproportionately advantaged. That all
amino acids are advantaged to the same degree (relative to the undigested fraction) suggests a
mass effect, such as changed gastric residency. Enzymes that can directly hydrolyse undesirable
microorganisms is also possible but again is under-researched in a feed context.
Enzymes and Gut Health
Gut-health is a widely used term and though it is not clearly defined, it is understood to mean a
gut which is generally free from any adverse exogenous challenge and is functioning optimally.
There are many diet, microbial and environmental factors that will reduce the health of the GI
tract of pigs and poultry (Klasing, 1998). Such factors include certain types of fibre, trypsin
inhibitor, phytate, lectins, undigested protein in the distal GI tract, pathogenic and putrefactive
microorganisms, diets with poor nutrient balance, temperature stresses, poor water quality,
certain vaccination programs and many others. Enzymes have been shown to beneficially
influence several of these metrics of gut health and so improve the enteric resilience of the
animal (Bedford & Cowieson, 2012) but the mechanisms involved are not fully explained.
Enzymes may increase both the rate and completeness of protein, starch and fat digestibility,
shifting the site of metabolism more proximally in the GI tract. This will reduce substrate
availability for the microflora in the ileum and caecum and also reduce the length of the intestine
with a consequential sparing effect on maintenance energy demand. Enzymes may also reduce
the negative effect of various dietary antinutrients such as phytate (Cowieson et al., 2004) and
fibre (Angkanaporn et al., 1994). Additionally, enzymes improve the digestibility of a range
of conditionally essential nutrients such as Gly, Ser, Pro, Phe, Zn and Fe which may become
particularly important during disease challenge or post-vaccination recovery (Klasing, 1998).
Thus, enzymes may impart a general ‘sparing’ effect on nutrient requirement, reducing visceral
mass, improving immune competence and enteric resilience in addition to the more conventional
influences on nutrient digestibility.
Conclusions
It can be concluded that development of new enzyme technology over the next decade will be
more challenging than has been the case in the last decade. Not only is the ileal digestibility of the
nutrients that drive diet economics relatively high but there is increasing competition from other
micro ingredients and a more challenging regulatory environment. It is likely that ingredient
quality assessment will become more widespread in order to strategically align enzyme choice
with the undigested nutrients in the feed. Furthermore, new enzyme candidates will emerge in
novel areas such as microbial and environmental management that do not compete directly with
incumbents for space in feed formulation. Finally there will continue to be progress in existing
enzyme sectors including new xylanases, glucanases, proteases and phytases that have enhanced
characteristics compared with existing products. Feed enzymes have a bright future and allow
nutritionists more freedom in formulation and contribute tangibly to sustainability of animal
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