Optimising phytase investment Optimising the use of feed raw materials will be central to feeding the increasing population without damaging the world we live in. So how can we use feed raw materials more effectively? Feed enzymes, especially phytases, may be one solution – by counteracting any negative effects caused by the anti-nutrient: phytate.
BY ADAM SMITH, DSM
y 2050 the world’s population is expected to surpass nine billion. The UN Food and Agriculture Organization (FAO) has estimated that this will lead to a 60% increase in the demand for high quality protein in the form of milk, eggs and meat. To successfully meet this demand without damaging the world in which we live, production systems will need to become more environmentally friendly and socially responsible, while still enabling producers to generate a profit. All nutritional solutions need to be tailored to the specific diet for which they are considered. To do this, nutritionists need to know the precise composition of the raw materials that they are using to formulate diets and this can be achieved through the use of NIR (near infra-red) spectroscopy. Substantial variation has been found in the nutrient concentrations of raw materials and so now there is a bold move towards more precise and accurate feed formulation which takes such variation into account. This ‘intelligent nutrition’, as it’s called, is what is needed to optimise production efficiency and improve sustainability.
Table 1 – Variability of phytate levels in some commonly used raw materials. Raw material MIN Phytate P level (g/kg) MAX Phytate P level (g/kg) Wheat 1.9 2.7 Corn 1.6 2.6 Sorghum 1.4 2.4 Rice Bran 10.8 11.1 Soybean meal 2.8 3.3 Oilseed Rape (Canola) 3.4 4.8 Deckhouse & De Paepe (1994) AFST, 47 : 19-29; O’Dell et al. (1972) JAFC, 20: 718-808.
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Figure 1: Phytic P – Broiler growing feed 20.00 18.00 16.00 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00 0.14
In-feed Phytate-P content %
Phytate versus phytase Phytic acid is a molecule made up of six phosphate groups bound to inositol. As the storage form of phosphorus, it is found in all common plant-based feed ingredients. It binds important nutrients, including calcium, iron and amino acids, to create phytate, the salt of phytic acid. When bound in this way the nutrients become unavailable to the animal. This costs producers money because more nutrients then need to be added to the diet than otherwise required and causes environmental pollution when unused nutrients are excreted. Once in the low pH conditions of the stomach, phytate is solubilised releasing bound calcium and amino acids, leaving free phytic acid. More than 80% of this phytic acid has the potential to be digested by phytase. Adding a microbial phytase to the diet is the best way to ensure as much as possible of this phytic acid is degraded in the short time it remains accessible in the stomach. This, in turn, means that there is
less remaining to re-bind nutrients as the pH rises in the small intestine, meaning more nutrients remain available for uptake in the animal and less are excreted. Balancing the phytase concentration added to the feed against the amount of phytate present will maximise the release of nutrients for the animal while also producing less waste, which is both economically and environmentally beneficial.
Phytate content variability Phytate phosphorus levels in commonly used raw materials vary markedly (Table 1) due to various factors, including crop genetics, harvest year, growing conditions, latitude, climate, fertiliser application, storage and processing methods. With such wide variations it is clear that relying on published values for ingredient phytate content has its limitations, particularly when multiple raw materials are combined. Figure 1, for example, shows what effect the variation in ingredient phytic phosphorus content has on feed levels in European broiler grower/ finisher feeds. There is significant variation between feeds with clear phase differences in the phytate concentrations seen. Higher phytate levels are typically found in starter diets, as they tend to contain higher levels of soybean meal. So the question
for nutritionists is: can average phytate concentrations be relied upon to decide on phytase additions? Clearly not.
Intelligent phytase nutrition Just like any other enzyme and its substrate, the level of phytase added needs to match the amount of phytate present in the diet. If too little phytase is added, not all the phytate will be broken down. Birds will not be able to use all of the protein, calcium and phosphorus in the diet because a proportion will remain inaccessible. This wastes money spent on the diet and is potentially damaging to the environment. If too much phytase is added, all the accessible phytate will be destroyed, but there will be an excess of enzyme. Thus costing the producer money. Getting this balance right is at the heart of DSM’s Intelligent Phytase Nutrition concept. The first step is to measure how much phytate there is in a given diet.
DSM has tested many thousands of feed and raw material samples, using both NIR and wet chemistry methods. This has enabled the company to devise a robust phytate-P NIR equation for ingredients and complete feed. PHOTO: FOSS
Feed analysis In the past we have relied on wet chemistry to measure phytate-P but this is slow and costly to conduct on a routine basis. By contrast, NIR spectroscopy testing offers a fast, reliable and economical way of checking levels in raw ▶ POULTRY WORLD | No. 2, 2021
NUTRITION ▶▶▶ Table 2 – Factors Effecting Accessibility of Phytate to Phytase. Positive factors influencing the Negative factors influencing the accessibility of phytate accessibility of phytate • Water pH <6 • Water pH >8 • Water temperature <20° C • Water temperature >30° C • Dietary calcium <0.9% • Phytate: protein ratio <0.04:1 • Phytate: protein ratio 0.05:1 • Dietary chloride concentration > 0.25% • Dietary chloride concentration <0.25% • Presence of protease & carbohydrases • No protease or carbohydrase use • Most phytate come from cereals & grain • Substantial concentration of phytate from legumes, little from by-products by-products such as rice bran • Presence of acidifiers • No acidifiers in the diet or water • No therapeutic use of Zn or Cu • High concentrations of Zn or Cu • Low viscosity cereals • Highly viscous cereals
materials and finished feed. This method uses the near-infrared region of the electromagnetic spectrum to determine the quantity of specific molecules present in a material. DSM has tested many thousands of feed and raw material samples, using both NIR and wet chemistry methods. This has enabled the company to devise a robust phytate-P NIR equation for ingredients and complete feed. This allows rapid and cheap measurement of the amount of Phytate-P in a given sample. Such a dynamic analytical tool combined with an accurate prediction model may be the ideal solution for optimum phytase dosing. By knowing the level of phytate-P in the feed, it becomes easy to determine the most effective phytase dose to add to the feed. Figure 2 shows the relationship between phytate-P measured, phosphorus release and the dose of phytase needed to achieve this level of phosphorus release. On the X axis we have Phytate-P concentration as measured in feed, and the Y axis shows the amount of a vailable
Figure 2: The phytate-phytase nutrient space in practical diets. 0.25 Zone 1
3000 FYT/kg 2500 FYT/kg 2000 FYT/kg 1500 FYT/kg 1000 FYT/kg
Available P release (%)
Zone 2 0.05
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phosphorus that you want to release with your phytase. This graph can then be subdivided into three distinct zones. • Zone 1 (Phytate-P limiting) – Low Phytate-P in the diet: high phytase levels are unnecessary because the substrate is limiting, adding more phytase will not release more phosphorus. You need to be careful as you may be overestimating how much phosphorus you are releasing with your phytase. • Zone 2 (Phytate-P not limiting) – Perfect balance between Phytate-P and phytase dose. • Zone 3 (Phytate-P in excess) – High Phytate-P concentrations; higher levels of phytase will release more phosphorus. The limiting factor in this case is phytase concentration.
Benefits for all By accounting for variable dietary phytate levels, nutritionists can achieve a better balance between phytase dosing and phytate level, thus destroying as much of the anti-nutrient as possible at minimum cost. This Intelligent Phytase Dosing benefits producers, birds and the environment. Flock performance, uniformity and feed costs are improved. Improved gut health will also be seen, leading to better litter quality, improved bird welfare and greater skeletal integrity. For the sustainability of the industry and compliance with local pollution and welfare restrictions, less nitrogen and phosphorus will be excreted, thus benefitting the environment.
Fine tuning – accessibility of phytate to phytase In the model described above, phytate accessibility is assumed to be 80%. This is an excellent estimate for modern phytases but can vary based on many factors, such as calcium level and source, choice of raw material, the use of acidifiers and even the presence of other enzymes. Table 2 shows the main interacting factors which can either increase or decrease phytate accessibility. DSM has taken all the latest information on these factors into account and developed a model to predict their impact, so that nutritionists can optimise phytase dosing even further.
Careful alignment Intelligent Phytase Nutrition is the DSM system of precision phytase dosing. For accurate phytase dosing, first the amount of substrate (phytate) in the diet is determined. With this value in mind, the most efficient level of phytase supplementation is then calculated to remove as much of the phytate as possible. This careful alignment of dose and substrate not only optimises the phytase investment but also maximises the precision with which feed raw materials are used, thereby improving animal production efficiency and reducing the environmental footprint. References available upon request