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Chapter 17. Material Flow in Feed Manufacturing 1/


1/ Lecture was presented by G. Walker

P. Raven and G. Walker
Western Farmers Association
Seattle, Washington


The technology of feed processing has undergone substantial improvement in recent years. It was only sixty years ago that feeds tuffs were mixed on the warehouse floor by the use of a shovel. Feed processing has progressed from the simple mixing of several ingredients by hand to mechanical mixing, to continuous mixing, and now to computer controlled mixing and pelleting. However, the basic concept of mixing ingredients together to result in a nutritionally balanced feed, has remained unchanged.

To accomplish the mixing of different ingredients, grinding these ingredients to similar particle sizes, and then putting them together in a single unit, requires a considerable amount of specialized equipment and technical expertise. Some feed plants are designed for specific functions, such as making poultry feeds exclusively; others are designed for producing a variety of feeds. Regardless of the specific purpose of a feed plant, material flow follows a basic pattern (see Figure 1).


The first operation in the feed processing plant involves the receiving of raw materials into the plant premises. Feed ingredients arrive in sacks, or other small containers, and in bulk.

Sacked ingredients are checked for identification and condition. They are then logged in after segregation of drugs and medications. Sacked ingredients must then be stored in a dry location with proper protection from rodent and insect infestation. Sacked stocks are then rotated to minimize staleness, product degradation, and insect infestation.

Bulk ingredients are handled according to their physical form. Liquid ingredients, such as oils and molasses, are generally stored in bulk tanks. Proper storage temperature is maintained and the filter screens are checked periodically. Solid bulk ingredients such as grains, oil meals, etc., are cleaned with a scalper to remove foreign material prior to storage in bins. Bin temperatures are monitored to prevent heating due to grinning respiration.


Material flow during processing includes:

(a) particle size reduction,
(b) premixing,
(c) mixing,
(d) pelleting, and
(e) sacking.

Coarse ingredients pass over a permanent magnet which removes tramp metal and then through a hammer mill which reduces particle size to the desired screen analysis. Ground material is monitored periodically to ensure size uniformity and to help detect wear of hammermill screen and hammers. The ground material is then routed to ingredient holding bins.

There are two mixing operations in feed milling. One is for the mixing of micro-nutrients; the operation is generally termed pre-mixing. The other mixing operation involves the actual blending of all components of the diet.

Micro-nutrients, such as vitamins and trace minerals, are accurately weighed with carrier material which has a density approximating that of the predominant micro-ingredient. The materials are then mixed in a batch mixer for a period of time specified by the equipment manufacturer to ensure homogeneity. The premix is finally routed to the premix holding bin.

Diet mixing begins when augers are set in motion to deliver; the correct amounts of each ingredient including the premix, according to the formula, into the mixer. Where manual changing of the mixer is done, ingredients are weighed out in sacks or hopper carts. The mixing period is according to the equipment manufacturer's specifications, but final mix is checked periodically with a tracer to ensure homogeneity of the mix. If the mixed diet is to undergo pelleting, it is routed to the pelleting bin.

Mixed feed mash for pelleting is first conditioned with steam in the steam conditioner section of the pellet mill, after which it enters the die where it is finally extruded. Freshly extruded pellets are hot and contain excess moisture which is removed during passage through the cooler. Fines are then screened from the cooled pelleted feed and returned for repeating. Fish oil, if added, is now applied prior to the routing of the finished pellets into the packer bins.


Most fish feed pellets are sacked. The sacking operation includes: weighing, sacking, taping, coding, and sewing. The sacked bags are then sent to the warehouse for distribution.


Bulk products are stored in large bins. Feed is loaded into specially constructed bulk carriers and delivered to the customer. Feed is discharged from the truck into customer storage facility by means of an auger system, paddle conveyor, or pneumatic system.

Fig. 1 Material flow diagram

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