Benefits of destruction of lower phytate esters

MIKE BEDFORD
RESEARCH DIRECTOR, AB VISTA FEED INGREDIENTS MARLBOROUGH, UK

Phytase has traditionally been used as a means to recover phosphorus (P) from phytic acid and thus reduce feed costs by enabling reduction of inorganic phosphate sources. More recent work has indicated that benefits beyond provision of P are achievable if sufficient phytic acid is hydrolysed. Initial work focussed on simply the destruction of phytic acid (IP6), and inverse correlations between animal performance and dietary IP6 levels noted. More recent work has investigated the kinetics of phytase activity in vivo and in vitro and both show that use of industry standard levels of phytase significantly reduce IP6 levels as expected, but increase levels of tetrakisphosphate (IP4) and trisphospate (IP3) in vivo.

The latter was not expected. If IP4 and IP3 do possess antinutritive capabilities, and evidence is provided here which suggests this may be the case, then in order to successfully implement an ”extraphosphoric” effect (superdosing) with a phytase, the target should be removal of all IP esters in the intestinal contents. There are large differences between phytases with regards to their kinetics not only on IP6, but also pentakisphosphate (IP5), IP4, IP3 and diphosphate (IP2). It is unlikely, therefore, that the dose required to ”superdose”, where ap
proximately 85% IP6 hydrolysis to IP1 is targeted, is a simple and consistent multiple of that required to release 0.10% available P (AvP), where only 40% hydrolysis is necessary. Successful superdosing could significantly improve amino acid digestibility and hence knowledge of the source of the phytase is essential if the correct dosage is to be employed to unlock these benefits

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