Phytase: A review of practical application

Dr. Kevin Herkelman

Phosphorus is a critical nutrient required by all animals. The main role of phosphorus is to support skeletal formation, mainly bones and teeth. Nearly 80% of the body’s phosphorus is contained in the bone. Phosphorus also plays a key role in carbohydrate metabolism, fat metabolism, lean tissue deposition, and as a component of phospholipids, which are important for proper cell structure.

Table 1 shows the phosphorus content of typical ingredients used in poultry and swine feeds. Plant-based ingredients like corn, wheat, soybean meal, wheat middlings, and Distiller’s Dried Grains with Solubles (DDGS) are fairly low in phosphorus

Table 1. Phosphorus Composition of Ingredients Used in Poultry and Swine Feeds

content. A typical combination of corn and soybean meal (the most common ingredients used in poultry and swine feeds) will provide less than half of animal’s requirement of phosphorus.

Animal byproducts such as meat and bone meal and poultry byproduct meal contain much higher levels of phosphorus than the plant based ingredients and can be important sources of phosphorus in animal feeds. Dicalcium phosphate, an inorganic phosphorus source, contains a high level of phosphorus compared to plant and animal based ingredients. However, due to cost, inorganic phosphorus sources are typically only included in the diet at levels to fill the gap between the animal’s phosphorus requirement and the level of phosphorus provided by other dietary ingredients.

Unfortunately, not all of the phosphorus in feed ingredients is available to animals for productive purposes. In grains and seeds, this is due to phytate. Phytate is a complex molecule that binds phosphorus (and other nutrients) for storage in seeds and grains. Between 60 to 70% of phosphorus in plant based ingredients occurs as phytate bound phosphorus. This phytate bound phosphorus is unavailable to the animal, because the digestive tract lacks adequate amounts of the enzyme (phytase) necessary to release the phosphorus from the phytate complex.

Table 2. Comparison of a Swine Diet With or Without Phytase

Phytase is an enzyme capable of releasing phosphorus from the phytate complex in grains and seeds. This phytase is a specific, commercially-available phytase product added to the diet to release phosphorus. Any phosphorus released by phytase from ingredients is then available for use by the animal to meet phosphorus requirements and to be used for productive purposes.

Phytase activity is typically expressed as “phytase units” or “FTU” per unit of feed. In general, 500 FTU of phytase per kilogram of feed liberates 0.10% phosphorus from dietary ingredients. In addition, this level of phytase also liberates calcium and other nutrients bound to the phytate molecule.

Table 2 shows a comparison of a swine grow-finish diet formulated with and without phytase. The addition of phytase decreases the amount of supplemental phosphorus (dicalcium phosphate) required to be added to the diet. In addition, the amount of supplemental protein (soybean meal) is also reduced.

The total amount of phosphorus in the diet is decreased 0.10% (0.50 to 0.40%). However, the amount of available phosphorus (the amount of phosphorus available to the animal for productive purposes) is the equal between the diets. This is because we are making more of the phosphorus from dietary ingredients “available” when phytase is added to the diet. In addition, feed cost is substantially decreased due to the competitiveness between suppliers of commercially-available phytase and the high cost of inorganic phosphorus supplements.

One major advantage of using dietary phytase is reduced phosphorus excretion. The phytase containing diet in Table 2 indicates total phosphorus in the diet can be reduced 0.10% with less inorganic phosphorus supplementation. This reduction in total phosphorus in the diet results in a similar reduction in the amount of phosphorus excreted by the pig (phosphorus not used by the pig).

Table 3. Effect of Phytase on Phosphorus Excretion

Table 3 demonstrates the effect of using phytase on phosphorus excretion. Experimentally, daily phosphorus intake was equalized between pigs fed diets with and without phytase (not done practically), the digestibility of phosphorus was increased nearly 11% when phytase was added to the diet. The addition of dietary phytase decreases the amount of phosphorus excreted through the feces by approximately 17%.

The decrease in phosphorus excretion determined experimentally has also been evaluated on a practical basis. Table 4 illustrates the effect of reduced phosphorus diets on total manure phosphorus excretion and the amount of land required to manage the level of phosphorus. The ability to reduce phosphorus level through the use of phytase resulted in a 31% reduction in phosphorus excreted. This resulted in a reduction in the amount of land required to handle the phosphorus excretion in the two types of manure storage systems analyzed.

Table 4. Manure Phosphorus Excretion and Land Required to Manage Excretion in a 1,000 Head Capacity Pig Finishing Building

In summary, phosphorus is a critical nutrient required by poultry and swine. Unfortunately, a significant portion of the phosphorus in typical ingredients is unavailable for productive use by animals due to the phytate complex. The use of dietary phytase releases previously unavailable phosphorus, reduces the amount of supplemental phosphorus, and reduces feed costs. In addition, phosphorus excretion and the amount of land required to handle excreted phosphorus is reduced when phytase is added to poultry and swine feeds.

Research Update: Pullet Feeds

Dr. Kevin Herkelman, Technical Services Manager

Wenger Feeds utilizes its three research barns to conduct trials on ingredients, feed formulas, management techniques, and breeds. Two recently completed trials led to some changes in the company’s pullet feeding programs.
Pullet Feed Energy
In April 2009, Wenger Feeds completed research to study how energy levels effect the growth of Hyline W-36 pullets. Achieving optimal feed intake and body weight targets during the growing period is a challenge faced by many using high producing, lighter body weight birds. Elevated energy intake has been shown to increase body weight in pullets, and the goal of the study was to compare three different energy levels. During the study, which was held at a pullet research barn, the flock was split into three separate groups of 18,000 birds each.
Results: Performance was excellent for all pullets and livability and body weight targets were met in each group by week 17. The high energy formula yielded the lowest feed intake and best feed conversion to 17 weeks of age. An increased growth rate was also noted in the high energy group during the last 2 weeks. However, this improved feed conversion benefit was offset by a higher cost per ton, and feed cost was equal among the three groups.
Conclusions: Based on this research, it is confirmed that the Wenger Feeds PG line of pullet feeds deliver maximum performance and efficiency at the correct energy levels. This research was conducted in a real production environment to ensure accurate results that can be put to work in your pullet barn.
Pullet Feed Using DDGS
In August 2009, Wenger Feeds completed research to study how Distiller’s Dried Grains with Solubles (DDGS) impact performance of a Hyline W-36 pullet. University trials have proven that DDGS may be used in relatively high levels in layer feed without affecting performance; however, the use of DDGS in pullet feed has not been widely researched. This study was held at a pullet research barn, where the flock was split into three separate groups of 18,000 birds each. Three different DDGS levels were fed, and performance and feed cost were evaluated.
Results: At 18 weeks of age, the two diets containing higher levels of DDGS had superior feed conversion and body weight. Livability exceeded breeder standards, and performance was very good in all three groups. As the level of DDGS increased, feed costs decreased. At the time this study was completed, the high DDGS level represented an approximate $0.05 per bird savings through week 18 in lower feed costs.
Conclusions: Feeding increased levels of DDGS to the Hyline W-36 pullet can reduce feed costs through 18 weeks of age. Body weight and livability can be maintained at very good levels. As a result of this research, the Wenger Feeds pullet feeding program has been adjusted to include more DDGS to maximize performance and efficiency.
To receive more detail on either of these research trials or to understand the potential benefit in your flock, please see your account leader.

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