The active substances contained in an animal feed additive can be a single ingredient or complex mixture of enzymes, binders, phytochemicals, live microorganisms and organic acids. Whatever their nature, they have to be fed to the target animal in a form that ensures the substance will be delivered, reliably, to the targeted site of action within the animal and still be 100% active.
A variety of techniques
Because of the diverse nature of the active substances, different formulation techniques have to be used for different products. For example, enzymes and microorganisms can be quite fragile, so it is usual to dry preparations containing enzymes and microorganisms to preserve their activity. For microorganisms, this is often performed by freeze-drying (lyophilisation) of stabilized cell cultures, while spray drying or fluidized bed drying, granulation and coating can be used for enzymes. When the active substances are volatile liquids, such as phytogenic essential oil preparations, alternative formulation techniques such as encapsulation are required to protect the volatile active substituents.
Alternatively, we may sometimes desire the feed additive to be a liquid preparation such as an enzyme for post-pelleting application. In this case, the added challenge involves stabilization of the active substance while ensuring the product can be reproducibly applied to finished feeds.
The density and size of the feed additive preparation will determine whether the active substance can be effectively and accurately distributed throughout the feed.
In general, successful formulation of feed additives must overcome three distinct challenges –homogenous distribution, thermostability and controlled release— in order to achieve the best results in animals.
Challenge 1: Homogenous distribution
The first challenge for the bioactive ingredient formulator is to ensure that the product is accurately distributed throughout the feed. Feed additives are always micro-ingredients and are typically added at an inclusion level around 100g per ton of feed. The density and size of the feed additive preparation will determine whether the active substance can be effectively and accurately distributed throughout the feed. For example, the average 4mm broiler feed pellet weighs 0.055g which equates to over 18 million pellets per ton of feed. To ensure every feed pellet received the active substance would require there to be at least 18 million particles of the active substance in a typical 100g inclusion. Such a calculation should always be performed to determine the optimum size and size distribution of the active preparation.
Challenge 2: Thermostability
The second challenge is that the active substance has to survive subsequent steam conditioning and pelleting where the feed and included additives are subjected to high temperatures (in excess of 85°C), elevated moisture content and high physical pressures. Considerable success has been achieved in protecting enzymes through this process by drying the enzyme inside a granular matrix and applying a single or multiple coatings onto the granules. Both processes were achieved by fluidized bed processing (Figure 1). Fluidized beds can be used to gently dry sensitive active substances but can also be used to form granular materials which makes the product much easier and safer to handle as there is reduced or no dust and the products are easier to disperse accurately in a feed matrix. Figure 1 illustrates a laboratory-scale machine with a batch size up to approximately 1kg. Larger, pilot-scale, full industrial-scale and continuous-flow machines also exist which can granulate and coat materials at ton per hour scale.
Figure 1. Laboratory-scale fluidized bed dryer, granulator and coater.
The formulation of a feed enzyme can even result in a product that performs better than inherently thermostable competitor products. Figure 2 shows the recovery of an inherently thermostable feed enzyme together with a thermo-labile (regular) and coated thermo-labile enzyme which had been added to feeds and pelleted at three different temperatures. The coating of the regular enzyme resulted in a product with over 70% recovery at 95°C and clearly outperforms even the inherently thermostable, engineered enzyme.
Figure 2. Recovery of enzyme activity from feeds conditioned at different temperatures.
The formulation of a feed enzyme can even result in a product that performs better than inherently thermostable competitor products.
Challenge 3: Controlled release
The third challenge is to ensure the active substances are available in the desired part of the gastrointestinal tract of the target animal. Care must always be taken to not encapsulate or coat a product to such an extent that availability and effectiveness in the animal is reduced. However, the formulation of an active substance can be used to direct where an active is available, or to protect a substance while passing through one part of the gastrointestinal tract—for example, gastric or rumen protection for a product that needs to work in the lower gastrointestinal tract.
The recently launched Biomin® Duplex Capsule that gives Digestarom® DC its name illustrates the power of product formulation. The inner core of the capsule contains the essential oils and substances that are active in the lower gastrointestinal tract of the animal. These are matrix encapsulated to enable their release throughout the lower gastrointestinal tract while protecting them from release in the stomach and enhancing the palatability of some components. Further palatability enhancement was achieved by applying a second essential oil substance in the coating matrix which is immediately available to the olfactory and gustatory senses of the animal. Figure 3 is an electron micrograph of a duplex capsule clearly showing the core and coat regions.
Figure 3. Electron micrograph of a Biomin® Duplex Capsule.