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Introduction of Feed Manufacturing Process

The process of manufacturing animal feed is a means whereby raw materials of widely ranging physical, chemical and nutritional composition can be converted into a homogenous mixture suitable for producing a desired nutritional response in the animal to which the mixture is fed. The process is basically a physical one and chemical changes are few. It should be remembered however that some raw materials will have undergone extensive processing prior to inclusion into a mixed feed, for example, extraction of oil from oilseeds by solvent or mechanical extraction, heat treatment of soya beans or other beans to denature anti-nutritive factors, or the production of fishmeal and meat meal.

The feed manufacturing process may be considered to be made up of several unit operations which, in almost all circumstances, include the following:

***raw material, storage and selection
***raw material weighing
***raw material grinding
***mixing of dry ingredients and addition of liquids
***pelleting of mixed feed (optional)
***blended feed bagging, storage and dispatch.

Their sequence and the size and sophistication of equipment vary with the output of feed required as well as differences in manufacturer's design.

Selection and layout of feed milling equipment

Selection must include the proposed capacity of the feed mill, the types of raw materials available, the types of livestock feed to be produced, and the characteristics of the power supply available. There are no set specifications for the layout of a feed milling operation, each being designed according to individual circumstances. The planning of larger mills requires the services of skilled engineers and draughts men, but small mills can usually be assembled from modules supplied by equipment manufacturers.

Raw material, storage and selection

In order to ensure a continuous supply of raw materials at the mill, when some may only be seasonally available on the market, and to take advantage of price fluctuations, some form of storage will be necessary. The particular method chosen for raw material storage will depend on the local circumstances, but in areas where labor is cheap and plentiful and capital funds scarce, it is likely that storage in bags will be preferable. Raw materials should arrive in good condition and in sacks which have not been used for the storage of fertilizer, pesticides or chemicals.

Raw materials will vary from country to country and from region to region and will have widely ranging bulk densities (weight for a given volume). These differences in bulk density must be taken into account when determining the space required for the storage of raw materials and finished products.

The proper storage of raw materials and of finished feeds is not only essential to prevent physical losses, but is also an important aspect of quality control which will be discussed in more detail later.

Raw material weighing

The weighing of raw materials requires great care and inaccuracies must be kept to a minimum. It should be noted that errors in the weighing of small quantities of raw materials often have far greater influence on the growth performance of animals than errors in the weighing of large quantities of material, for example, the omission of say, 25 kg of bran from a mixture requiring 400 kg of bran is of much less significance nutritionally than the omission of 1.5 kg of vitamin pre-mix say from the same mixture requiring only 2.5 kg of pre-mix. It may therefore be necessary to purchase a scale to weigh small quantities, of up to 25 kg, with an accuracy of ±100g and a greater capacity scale, for example up to 500 kg with an accuracy of ± 2.0 kg. The use of accurate scales is of particular importance when handling expensive and/or potent raw materials such as vitamins and medicinal additives which are added at low inclusion rates.

Raw material grinding

In the sequence of unit operations involved in feed milling, raw material grinding may occur before or after weighing. It is a process with high power requirements which is often noisy and dusty. Because of difficulties experienced in feeding certain raw materials (for example, brans, cottonseed cake) through a grinder, many feed machinery manufacturers pre-blend ingredients before grinding in order that the more easily ground materials will act as carriers or flow aids to those offering resistance to grinding.

It should also be noted that the desired fineness of grind will be influenced by the livestock to which the feed must be fed, or by other processes following grinding. Raw materials for poultry should be more finely ground than for cattle or pigs and raw materials to be pelleted are usually more finely ground than the equivalent feed as meal.

Mixing of dry ingredients and addition of liquids

It is the job of the mixing machinery to produce a homogenous blend of all the raw materials desired in a formulation, such that at each feeding period each animal receives a balanced mixture of nutrients. Not only are their requirements more demanding, but the daily nutrient intakes of those eating small amounts of feed will be subject to much greater variation as a result of poor mixing. Mixing often improves feed palatability if one or more of the raw material is unpalatable to livestock.

Pelleting of mixed feed

Pelleting involves the compression of a mixed feed through holes in a hardened steel ring or plate (a die) by means of hardened steel rollers. The die forms the feed into pencil-like extrusions which are cut by knives into pellets of desired length on leaving the die. In a ring die pelleter, the rollers or the die may be driven but in a plate die pelleter the rollers only are driven. The die and rollers of a ring die pelleter may operate in a horizontal or vertical plane according to machine design. Pelleters with horizontally running dies are most commonly found in farm-scale feed mills. The pelleting process is very energy intensive, demanding up to 50% of the total power required for feed manufacture. The diameter of feed pellets is governed by the diameter of the holes in the die ring but the smaller the die holes the greater effort is required to force meal into these holes, hence the greater the power demand, that is, the smaller the pellet, the greater the cost of manufacture.


Compound feeds, whether in meal or pellet form, are usually distributed in sacks in developing countries, although for on-farm use or for distribution to a large livestock unit distribution could be in bins or trucks. Bags may be filled directly from mixers or from holding bins and may be weighed on a scale balance or through an automatic pre-set weigher and bagging unit set to weigh.

Quality control

Quality control is essential at all stages in the production of compound feed if the maximum and most efficient returns are to be obtained by the feed compounder and livestock producer. In some countries the control of feed quality is regulated by government legislation, while in others there is no such provision. In either case, omission of any serious attempt at quality control is false economy in the longer term.

Other tests

In addition to the above factors, there are a number of other considerations to be borne in mind with specific types of materials. It is important to ensure that processed materials, particularly those of animal origin such as fish, meat and bone meal, do not contain any pathogenic bacteria which could cause diseases in animals to which they are fed. The most common pathogenic organism encountered is salmonella, and it is important that consignments, particularly from new suppliers of processed materials, be tested for this organism.

Finished feeds

If the raw materials and processing conditions are of the correct standard, then the product should also be of the correct standard. However, variations and errors can arise in the weighing or accidental omission of an individual raw material. The omission of a small quantity of vitamin supplement may have a marked adverse effect on the health and growth rate of animals receiving the feed. For this reason, considerable care must be exercised in ensuring that the specified amounts of all raw materials are weighed out for each batch, and an appropriate system for checking this should be devised. It is important that representative samples of batches be taken for check analyses to monitor the composition of the finished feeds. If results show deviations from the required composition, the reasons for this must be sought and rectified. In some countries there may be statutory requirements for the composition of feed offered for sale.

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