Animal Feed Processing

This extensive process refer to the use of grains, cereals, vegetable and animal by-products, oil and fats, molasses, vitamins and minerals to create a balanced formula for different animals in all the life stages to cover all nutritional requirements. After first cleaning the seed particle size reduction (grinding) is the next step in this process, all ingredients needs to be reduced in size to accomplish a homogeneous process into the mixer. Once ground, the ingredients are stored separately prior weighing and dosing and then mixing. In the mixer the ingredients remains for a certain amount of time (wet and dry mixing time) and then some liquids are added. From here the mash can go to two different processes, for pelletized feeds or extruded feed, these two processes involve starch gelatinization (total or partial) to create a feed pre-digestion effect and at the same time the bacteriologic level is reduced due to the high temperatures reached at the conditioners where live steam is used. Once molded (into pellet or collets) the feed is dried (if required), cooled, covered with liquids (fat/oil/enzymes/flavors coating) and then screened to remove fines prior bagging or bulk storage.

The main finished products from this process are: Poultry Feed, Swine Feed, Cattle Feed, Horse Feed, Pet Food, Fish Feed and Shrimp Feed.

Another part of this process is called Steam Flaking Grains which involves the digestion and utilization of starch in the ruminant animals. The processing of the grain plays a significant role in how the starch within the grain is presented to the rumen bacteria and how it is either broken down or its passed on for further digestion in the lower digestive tract, this also affects how the starch particles and compositional molecules are also presented into the digestive process.

  1. As the starch is broken down by the rumen bacteria, organic acids such as acetic and prop ionic acid are produced. While these two acids have different functions in the body and higher concentrations of one may be preferential over the other depending on the type of animal (i.e. a dairy cow vs. a feedlot steer) these acids are precursors for important metabolic pathways. Acetic acid enters a pathway by which fatty acids are produced while prop ionic enters that path which results in the production of glucose in the liver and is subsequently used for energy by the animal. Acetic acid can also be used for this process but it is a more indirect process and less efficient.
  2. As the starch particles and sub molecules are broken down the result is a supply of carbon skeletons which are available to the bacterial population. The microbes can combine these carbon chains with nitrogen (ammonia) cleaved from intake protein to form protein of their own (microbial protein). This protein makes up the majority of the protein available to the animal as the bacteria are passed down the digestive tract.

Based on this information, starch availability and digestion is required for two very major roles, i.e. energy and protein production.

The starch in corn is found in two main forms — amylase and amyl pectin. Both of these molecules are made up of chains of glucose molecules bound together in beta 1-4 linkages. In other words one glucose molecule is bound at its No. 1 carbon to the No. 4 carbon of the next and so on. Amylase is basically a straight chain of these glucose molecules while amyl pectin has many branches in the chain. The entire starch granule is made up of clusters of these molecules. Amyl pectin is more digestible than amylase because of its branched chain configuration. This simply provides more access points for starch digesting enzymes. Normal corn contains approximately 25 percent amylase and 75 percent amyl pectin. Research has shown that these numbers can be altered and the amyl pectin concentration can be increased through bioengineering. Obviously though this opens up a whole new can of worms.

It would appear at this point that the greatest effect on improving starch digestion in the rumen occurs when it is processed through a method such as steam flaking. Steam flaking subjects the grain to high temperatures and moisture in the steam cabinet. This allows the heat and moisture to enter the starch matrix of the individual kernel. Mechanical pressure is then applied which, when combined with the previous effect causes the starch to expand and disrupt. The term applied to this process is referred to as gelatinization. When exposed to water starch granule swell although without the applied heat the change may not be noticeable. Heating breaks the intermolecular bonds to allow significant swelling. This swelling of the starch-water mixture then becomes translucent and forms a "gel" as it cools and intermolecular bonds are allowed to reform. Because the amyl pectin molecules are branched, they interfere with themselves and cannot reform into a tight, firm structure, therefore leaving the starch matrix more open and susceptible to microbial and enzymatic activity. The degree of gelatinization is typically considered an indicative measure of the improved digestibility of the starch. Gelatinization values of 50 to 68 percent and higher are commonly observed in operations such as feed-yards which feed the flaked grain within hours of its production.

Additionally, there are several process parameters to be achieved in the process to obtain the best results on the steam cereal flaking process:

  • Cleaning; to remove foreign materials.
  • Treatment; some processors used to use surfactants or even water to treat the cereal grains prior the conditioning step.
  • Steam conditioning, refers to the injection of live steam into the steam chest reaching temperatures around 210-220ºF @ 100 PSIG on the piping line (manifold or distributor) with a retention time about 45-60 minutes depending of the desired cooking degree.
  • Flaking; by using a flaking mill to produce flakes at about 0.015"-0.018" thickness. Roll speed could be configured to achieve 450-480 RPM.
  • Drying/Cooling; this is only required if the finished product will be stored more than 48-72 hours after production, if the flakes will be offered to the cattle immediately after process dryer or coolers are not required.
  • Steam generation; a simply rule to follow in order to size a proper steam boiler will be 12 BHP per ton produced and taking in consideration 80-85% efficiency on the boiler.

The other part of the Animal Feeding Process is known as Full Fat Soybean Meal which is produced by cooking or roasting the soybeans. Full fat soybean contains high fat levels (+/- 20%) and is a good source of all the essential amino acids.

The heating effect in the cooking is required to destroy the anti-nutritional factor, trypsin inhibitor. If this trypsin inhibitor is not destroyed there will be reduced digestion of protein and growth can suffer. Care is needed not to prolong the heat treatment or to have the temperature too high, as this can destroy the nutrients in the meal.

High-shear extrusion processing deals with a short-time (20sec), high-temperature (up to 320°F) and high-pressure (40 atm) cooking condition which leads to rupturing cell wall, liberating oil, and protein de-naturation.

Consequently, lipolytic enzymes and anti-nutritional factors (trypsin inhibitors and urease) will be deactivated. The nutritional quality and amino acid digestibility of properly processed extruded soybean meal is remarkably better than conventional soybean meal (solvent). Typical US whole soybeans contain about 38% crude protein and 19.5% oil (acid hydrolysis).

The extruded full-fat soybeans have the same amount of protein and oil but lower moisture content.

By using extruded full-fat soybean meal in the poultry feed (TMEn: >3800 Kcal/Kg), there won’t be any need for added fat. Also, there won’t be a need for costly equipment to add fat to the diet in the feed mill (pumps, tanks…). Extruded full-fat soybean meal can also replace a considerable amount of the protein source in the diet.