THE USE OF HIGHER LEVELS OF PHYTASE TO REDUCE DIETARY INCLUSION OF INORGANIC PHOSPHATES

“Most poultry and swine diets are primarily composed of plant-based ingredients. In plants, phosphorus (P) is present in different forms such as attached to organic molecules like phospholipids and proteins, but the majority is present as part of the phytate-P, which comprises around 0.18 to 0.25 % in most common cereals. Phytate levels vary in feed ingredients and subsequently feed, and it is therefore critical to analyse these for phytate composition to allow for optimum phytase use to deliver reliable feed cost savings.”

Global concern about sustainability has prompted many countries to legislate to reduce pollution from phosphorus (P) and nitrogen. The use of microbial phytase in animal feeds has the potential to significantly reduce the concentration of P in manure by releasing P from phytate stored in raw materials, thereby reducing the requirement for supplementation of inorganic phosphate to animal diets. The P released from phytate degradation by phytase can be used to meet animal requirements and reduce the inorganic phosphorous content in manure.

Phosphorus plays a critical role in cellular metabolism, as a part of the energy (ATP) currency of the cell, in cellular regulatory mechanisms and in bone mineralization. Through its involvement in these metabolic and structural processes, P is essential for animals to attain their optimum genetic potential in growth and feed efficiency as well as skeletal de- velopment. Because of the key role of P in bone de- velopment and mineralization, the requirements of the animal for this mineral are highest in the young growing animal. In diets of non-ruminant animals, such as broilers, the challenge in P nutrition is how to best make available to the animal the P that is present in the diet.

Most poultry and swine diets are primarily composed of plant-based ingredients. In plants, P is present in different forms such as attached to organic molecules like phospholipids and proteins, but the majority is present as part of the phytate-P, which comprises around 0.18 to 0.25 % in most common cereals. Phytate levels vary in feed ingre- dients and subsequently feed, and it is therefore critical to analyse these for phytate composition to allow for optimum phytase use to deliver reli- able feed cost savings. Therefore, phytase suppliers should be able to assist in determining phytate-P levels in raw materials and diets. Then, based on the data for nutrient analysis, formulation should be reviewed to ensure enough substrate is available to release the desired nutrient release.

Phytate is poorly digested by monogastric ani- mals which is why phytase was introduced. With- out 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 pro- teins and minerals in the diet, reducing digestibili- ty 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 di- gestibility/availability. Several studies have reported that phytate increases the excretion of endoge- nous 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 man- datory feed additive. The use of phytase as a feed supplement proves effective in mitigating the nega- tive 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 in- organic 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 nutri- tional 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 on P-release. The latter depends on the efficacy of the phytase in finding the last remaining phytate molecules as well as on the ability of the phytase to release P from partially degraded phytate, such as IP4 and IP3.

The price of feed phosphates has increased dramatically during the last year (Graph 3). This has led nutritionists to look at the possibility of using phytase enzymes at higher concentrations (from 1,000 to 2,000 FTU/Kg) than they were normal- ly using (500 to 1,000 FTU/kg) aiming to release more P. Beyond the mineral matrices usually ap- plied (P, calcium and sodium), companies have also started to adopt strategies including additional matrix values in the formulate software, such as energy and amino acids. Prices of all raw materials and energy items (electricity, gas, fuel) have increased beyond record levels, due to the current economic and political situation.

One of the strategies that AB Vista promotes is to use higher doses of phytase than normally are being used (above 1,000 FTU/Kg) for the purpose of releasing the maximum amount of nutrients from phytate molecules to eliminate its antinutri- tional effect in the diet. In addition, it is being advised to employ a full matrix, based on mineral, energy, and amino acids rather than only the min- eral values (Graph 4). All of these recommenda- tions are supported by validation trials and a good knowledge behind the products, which make the matrices proposed robust and secure to be used safely. The recommendations for these higher lev- els were based upon a holo-analysis data set where confidence limits were included, providing addi- tional safety margins for nutrient releases. Data using Quantum Blue phytase (AB Vista) supports the use of higher doses of phytase (1,000 to 2,000 FTU/kg). These data suggest that greater phytate degradation occurs, removing the antinutrient properties and also releasing more P.

The animal response to phytases has been shown to be logarithmic. Therefore, as feed prices and thus the value of increased animal productivity increase (as they have done in the past years), it is more economically attractive to dose phytase at a higher level. However, as the dose response curve is not linear, the formulator needs to ensure that the appropriate matrix values are assigned to phytase when the inclusion rate varies.

The higher dosage phytase application with maximum use of nutrient matrix values is a novel and cost-effective tool in poultry and swine diets that improves environmental and financial sustainability and may be a cost advantage solution especially given the current prices of ingredients.