ARTICLE FEED & ADDITIVE MAGAZINE August 2022 63 Phytate is poorly digested by monogastric animals which is why phytase was introduced. Without the use of phytase, typical diets would need to be supplemented with substantial amounts (16-8 kg) of mineral phosphate, monocalcium phosphate or dicalcium phosphate (MCP or DCP), depending on the phase and the specie. Phytate. present in all plant-based feedstuffs, is known to bind with proteins and minerals in the diet, reducing digestibility and utilization of important nutrients. The enzyme phytase hydrolyses phytic acid, releasing P and eliminating its metal chelating capability and enhancing nutritional value of raw materials (Image 1). Use of phytase allows reformulation, reducing not only the amount of mineral phosphate required but can also help to reduce the inclusion of protein materials due to the impact of phytase (especially at high doses) on amino acid digestibility/availability. Several studies have reported that phytate increases the excretion of endogenous amino acids while use of phytase reduces the ileal flows of endogenous minerals and amino acids in broiler chickens. Our findings show that phytase should be a mandatory feed additive. The use of phytase as a feed supplement proves effective in mitigating the negative effects of phytate in livestock diets and provides an improvement on feed intake and body weight. With sufficient dietary phytate, a matrix for P can be applied, which would reduce the levels of inorganic phosphates in the diet. Indeed, with higher doses of more effective phytases, more inorganic P can be replaced by the phytase release. The amount of inorganic P removed from the diet formulation will depend on the dietary phytate content, dosage and type of phytase to be used as well as the nutritional matrix values applied. Graph 2 gives example levels of MCP in a broiler starter diet based on either wheat/soya beanmeal (diet 1) or corn/soya bean meal (diet 2). Typically, in grower and finisher feed, it will be possible to remove all inorganic phosphate from the formula. Different phytases can have different efficacies, not only when comparing products at standard level but also how increasing dose level impacts Image 1. Nutrients that can be released from breakdown of phytate molecules Graph 1. Phytate content of the main raw materials used for feed formulation (AB Vista internal data)
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