Effects of feed technology on feed-enzymes and feed safety
Today the use of microbial enzymes as feed additives, is a well-established practice and most of poultry and swine feeds in intensive animal production contains feed enzymes.
For over 20 years, phytases are added to non-ruminant diets, releasing organic phosphorus (P) which is stored as phytate in plant-origin feed ingredients, making it more available to animals. This reduces diet cost, because less inorganic phosphorus (phosphates) should be added to achieve the same performance.
Other enzyme categories, like proteases, xylanases, glucanases, amylases and pectinases can improve feed utilization, resulting in further feed cost reduction, improved animal performance, and reduced environmental impact.
Feed enzymes in some cases are added "on-top" aiming to improve animal performance. More often, nutritionists are assigning nutrient matrix values to enzymes for diet optimization. In this case, substantial diet cost savings can be experienced.
Nutrients & energy are "released" by the enzyme effects on various dietary components (substrates).
All these benefits that nutritionists are expecting from feed enzymes, can strongly contribute to feed safety and improved animal performance.
Feed manufacturing process is sitting between this advance biotechnology (feed enzymes) and their great benefits for animal production.
Feed manufacturing process
a. Feed Enzyme Storage.
Feed enzymes are protein in nature and their stability could be affected by temperature, oxygen, light and humidity. It is obvious that some of these factors are severe in tropical and sub-tropical countries and can affect enzymes which are un-protected (un-coated) or /and liquid. On the other hand, coated products can resist storage with excellent stability above 80% even at 35-40oC for about 1 year (Table 1).
Different feed enzymes have varying shelf-life, for specific conditions of temperature (25oC) and humidity. Feed mills should keep them in cool-dry place and limited exposure to air (oxygen) or light.
b. Pre-mixing or/and mixing (for dry enzymes only).
Premix containing trace minerals and choline chloride, could be harmful to some additives, including un-coated (not protected) feed enzymes. Again, coated enzymes can recover well in a such "environment" (Graph 1).
Dry enzymes are considered as added value additives and are included in the feed at small doses (50-500ppm). In this regard, flowability of dry enzymes is another important characteristic, which could affect the accuracy of dosing, both manual and automatic. Dusty products are not flowing easily and are more difficult to be distributed homogenously in the feed. Also, they are not safe for the feed-mill or premix-plant workers, as enzyme dust is allergenic.
DSM as a global premix producer, is evaluating additive and enzyme dustiness with special equipment, which is simulating the additive handling in feed-mill (Figure 1). The difference between the "other phytases" and the Granulated Thermostable (GT) product is obvious.
Nutritionists want enzymes to be homogeneously present and well mixed with the feed particles. The dustless nature of a product that is in a coated-granular form can help on this, together with enzyme particle number per dose of enzyme.
In Graph 2, four granulated phytases were compared for the number of particles that can be delivered through the feed to broilers. Phytase GT contains 12,000 granules per gr, while phytases A – B - C contain 2,900 - 8,600 - 9,400 granules per gram respectively. If these phytases (GT-A-B-C) will be included in broiler feed at their standard dose, 100 – 100 – 50 – 50 ppm respectively, then 100 gr of this feed will contain 120 particles from phytase GT and 29 – 43 – 47 from phytases A – B – C respectively. These lower feed particle numbers for products A – B – C, indicates a poor homogeneity, confirmed by the calculated higher CVs.
c. Feed hydro-thermal processing / pelleting (for dry enzymes only)
During the last 20 years, feed industry increased the degree and duration of hydrothermal processing, for better pellet quality, feed hygiene and utilization of alternative feed ingredients. Enzymes are proteins that have specific and complex 3-dimensional folder structures, which are essential for their attachment and interaction with the substrates. An unfolded enzyme molecule, exposes its active sites, leading to further de-stabilization, until its bio-catalytic properties will be irreversibly lost (Figure 2).
Some feed enzymes have inherent temperature stability properties of the enzyme protein itself, but in most of the cases these properties are not sufficient to withstand the hydro-thermal feed processing and thus a formulation of a product form is necessary.
Feed enzyme formulation process varies between different products, from a simple mixture of the enzyme concentrate with a carrier (which offers no protection to the enzyme protein during feed processing) in either mash form (Figure 3-A) or in micro-pelleted form (Figure 3-B), to the production of sophisticated coated granulates which offers significant protection to enzyme protein during feed processing (Figure 3-GT).
DSM & Novozymes Feed Enzyme Alliance, developed the most heat-stable dry feed enzymes, under the brand name RONOZYME. Through a patented process, high quality granulation & coating technologies were developed: GT (Granulated Thermostable) and CT (Coated Thermostable). The resultant granulates have exceptional physical and stability characteristics, protecting the enzymes through the feed production process. This coating is rapidly degraded following ingestion, releasing the enzyme activity in the animal's gastro-intestinal tract.
RONOZYME's GT & CT have excellent thermo-stability properties, especially in aggressive feed processing conditions, over powder and other granulate products. This has been demonstrated in many studies and trials. Three examples are highlighted below:
In Graph 3, Phytases CT & GT have a superior recovery when pelleting at 95oC, after conditioning for 90 sec. Phytase B is a coated granulate, while products C & D are un-coated micro-pellets. Phytases E & F which are uncoated, mash mixed with a carrier, almost disappear after pelleting.
In Graph 4, a protease CT, exhibits a very good recovery even if a Feed Mix Expander was included in the feed production line, before pelleting, challenging the enzyme at 120oC for 10-15 sec.
In Graph 5, a xylanase CT, shows an exceptional stability when compared with many commercial products having the same enzyme activity, in broiler feed treated at 90oC. Only three from the other commercial products (E, AA, AB) had an acceptable xylanase recovery.
d. Final feed
The final step of the feed manufacturing process is the feed itself. Feed enzymes which "survive" from the hydrothermal treatment are in contact with many feed ingredients and additives, until they are consumed by animals. Also, storage conditions of a final feed containing enzymes, can affect their stability. For example, feed stored in a metallic silo in tropical and sub-tropical regions, can be exposed to temperatures up to 50-60oC (in the silo). In Graph 6, pelleted feed stored at 25oC had no losses in 1 month and minor losses at xylanase activity after 3 months, when the added enzyme was Granulated Thermostable (GT).
Bioavailability of coated granulates GT & CT.
When a new formulation (coating) technology is applied, it is important to confirm that the enzyme activity is released under the application of relevant conditions, as easily as for uncoated products.
In Figure 4, the left jar with cold water contains an un-coated micro-pelleted phytase, which it seems to be well dispersed. The milky-white colour of the solution is due to the carrier and not due to phytase. The right jar with cold water contains a GT phytase with poor dispersion of the granulates as all of them will form a sediment. The simplistic/erroneous conclusion is that the later product does not release the enzyme, keeping it well enclosed in the special GT coating. However the graph of Figure 4, shows that if this GT phytase is added in a jar of water with pH 3.5 and temperature of 400C (right conditions), in less than 2 min, the 100% enzyme is released.
This is confirmed by in vivo data (Graph 7), where both liquid and Granulated Thermostable (GT) phytase were icluded in broiler feeds. The phytase efficiency (expressed in % of birds' Toe Ash) of GT form was not less than the Liquid, which supposed to be more available as an uncoated form.
Dry or Liquid Feed Enzymes ?
Feed industry has strong concerns on the dry enzyme application, due to the aggressive hydrothermal feed processing and pelleting. These concerns increased the interest for liquid enzyme usage, applied post-pelleting, by-passing heat treatment.
For feed producers, moving to liquid feed enzymes can result into higher operation complexity and significant capital investment. Furthermore:
• Liquid enzyme application systems need regular calibration and maintenance to ensure reliable and consistent dosing.
• As liquid feed enzymes are added post-heat treatment, attention is needed to ensure the cleanliness of the application equipment, for preventing feed microbial contamination (e.g. Salmonella).
• Liquid feed enzymes need specific equipment which can be expensive, depending upon the complexity and quality of the selected equipment.
• Liquid enzymes (contrary to dry enzymes) are concentrated on the pellet surface. This explains why in standard livestock pellets, the enzyme can be found in higher concentration in feed fines (produced from pelleted feed handling), than in pellets (Figure 5 & Graph 8). This is not the case for extrudate pellets (aqua feeds), which can absorb well the liquid enzyme, due to their porous structure.
On the contrary, dry feed enzymes in general :
• Are easier to handle by any size of feedmill.
• Are more stable than their liquid forms.
• Are frequently added via a pre-mixture (vitamin-mineral premix), sourced by a specialist premix producer. This means that dry enzymes can be dosed/included in the premix in accurate dosing system, while the liquid dosing accuracy is totally controlled at the feed mill.
• Are distributed in the whole body of pellets, meaning that both fines and residual pellet can have the same enzyme activity (Figure 5).
Although dry feed enzymes have significant advantages, in some feedmills the processing conditions could exceed their stability characteristics of even the most heat stable granulated products. In such case, the cost-effectiveness of an extradosing should be considered to overcome the procesing losses. If this option is not cost efficient, then the application of liquid enzymes could be a viable alternative option.
Feed enzymes are facing challenges during feed manufacturing process. Nutritionists and feed-mill managers/purchasers should be very careful when selecting feed-enzymes for their operations. Dry feed enzymes are the most convenient and reliable form for livestock feed, while liquid enzymes can be used in extruded feeds for aquatic species.
All dry feed enzymes are not the same. There are products in the market which are stable in the entire distribution and feed production chain, i.e. during storage, in premixes, during feed processing, and in finished feeds. DSM & Novozymes Feed Enzyme Alliance, developed special granulation and coating technologies (RONOZYME GT & CT), which had been proven to be the way to obtain the most pelleting stable products in the market, even in aggressively processed feeds, without compromising the bioavailability. In addition, granulation technology can ensure that the products are safe, easy to handle, dustless, with high flowability and mixability.
For more of the article, please click here.
Article made possible through the contribution of Kostas Stamatopoulos and DSM Nutritional Products Asia Pacific