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7.1 Losses and Deteriorative Changes which Occur During Feed Storage
7.2 Storage Procedures

All types of ingredient, as well as completed compound feeds, require special care during storage to prevent deterioration in quality, and loss. Additionally they are very valuable commodities and need to be subjected to careful stock control to prevent theft. Stock control is also essential to enable you to fulfill the feed needs of your animals adequately and to ensure that you have enough, but not excess, of each ingredient available for manufacture when needed.

Good storage is essential because the value of the feed that you present to your animals depends on it. Feed spoils during storage -whether it deteriorates quickly or slowly depends partly on its quality when you receive it but very largely on how you store it on your farm.

In this section of the manual, some of the losses and deteriorative changes which can occur during storage are described. Recommendations for storage procedures are then given. Throughout, it has been assumed that feed will be stored in bags or other small containers, not in bulk bins which are unlikely to be found on small farms.

7.1 Losses and Deteriorative Changes which Occur During Feed Storage

7.1.1 Physical Loss
7.1.2 Water and Heat Damage
7.1.3 Insect Damage
7.1.4 Fungal Damage
7.1.5 Chemical Changes During Storage

Environmental factors, such as moisture (feed moisture content and relative humidity), temperature, light, and oxygen influence deteriorative changes and losses in feedstuffs. These affect the feedstuff either directly or by influencing the rate of development of insects and fungi which consume the feed during storage.

The following are the major factors which affect the quality and weight of feedstuffs during storage:

a) major losses due to human theft, fire and the consumption of scavenging animals, such as rats and birds

b) damage due to rain and condensation, and to high temperatures

c) damage by insects

d) damage by fungi

e) changes in the quality of the feeds due to enzymatic actions and the development of oxidative rancidity

Of the above factors, (b) is probably the most important as it influences the rate of loss or damage caused by most of the others listed. Though oxygen (from air) is necessary for the development of oxidative rancidity and for the growth of fungi and insects, it is impracticable to exclude it from feed storage areas. Oxygen is sometimes replaced by nitrogen or carbon dioxide for the storage of specialized foods for humans but has to be accepted as omnipresent in feed stores.

7.1.1 Physical Loss

Significant loss can occur as an accumulative effect of individually small, but regular theft. Less obvious are the losses caused by scavenging animals, particularly rats and mice. Food stores are notorious breeding grounds for such animals.

Temperature increases sufficient to cause fire (see 7.1.2 and 7.1.4) can occur in stacked feeds. Feed stores are flammable, particularly if they are constantly full of fine atmospheric dust from grinding processes within the store or adjacent areas.

7.1.2 Water and Heat Damage

High levels of moisture content and relative humidity cause direct losses by making it difficult to use the material in its original form. It may be too wet to mix if it is an ingredient, or its physical structure may be destroyed if, for example, it is in pelleted form. More serious is the effect that high levels of product moisture and relative humidity have on insect infestation and the growth of fungi.

Regardless of the initial moisture content of the feed materials put into the store, their actual moisture content will gradually reach an equilibrium dependent on the relative humidity of the air in the store. Generally a safe moisture level for a specific product is that which develops at a relative humidity of 75%. However, relative humidities above this level in tropical areas are common; moisture levels in feeds therefore tend to rise. This is one of the reasons why it is sensible to store feeds for much shorter periods before use in tropical areas than in temperate zones. Cereals will store quite well at 10-12% moisture. In general, moisture levels of 10% or less should be sought. Fungal growth increases moisture content also.

High temperatures also affect the rate of loss and damage in feeds, another reason why feeds in tropical zones should not be stored as long as in temperate areas. High temperatures in feeds may occur not only because of environment and the way in which they are stored but because of the heat generated by the growth of fungi and insects. Increases in temperature within large stacks of feed have been known to cause 'spontaneous combustion' followed by fire losses. Increase in temperature may reduce the availability of the amino acids in feeds.

7.1.3 Insect Damage

Feeds are attractive places for insects, including various species of moths, weevils and beetles, which consume the feed. All grow well at normal temperatures in feed stores. At temperatures from 26-37° C they can reach epidemic proportions. Insects thrive better on ground materials. Whole cereals or oil cakes can therefore be stored longer than meals made from them. Insects cause damage through weight loss, the exposure of the feed to further damage by fungi and through oxidation, and the introduction of contaminating bacteria.

7.1.4 Fungal Damage

Fungi grow at relative humidities above 65%, moisture contents generally above 15% (although some mycotoxin producing fungi grow well at only 9-10% moisture) and temperatures which are specific to the fungal species. Most fungal growth occurs at temperatures above 25° C and relative humidities above 85%. Higher temperatures and moisture levels favour increased growth. Fungal growth itself encourages local rises in temperature and moisture content. Many fungi are killed during the processing of ingredients but their spores are resistant and remain present to re-infect the material later if the environmental conditions become favourable for their development.

Fungal growth causes weight loss, increases in temperature and moisture, staleness (off-flavour), discolouration and, perhaps worst of all, some common species produce mycotoxins (see Appendix XV). Mycotoxins, the best known of which are called aflatoxins, are known to be toxic to some species of fish at least. In addition, as the toxins remain in the flesh of the animal which consumes them, they are also a health hazard to humans. Sorghum, maize and its by-products, groundnut, cottonseed, cassava, coconut and sunflower are ingredients especially prone to contamination with mycotoxins.

7.1.5 Chemical Changes During Storage

The following deteriorative changes can occur in feeds during storage.

Lipids can break down into free fatty acids which make the feeds more prone to the development of rancidity. This breakdown can be caused by the damage resulting from insect infestation and fungal growth. High lipid ingredients are more susceptible to this type of chemical change than others. Carbohydrates may ferment, to produce alcohols and volatile fatty acids.

Lipids undergo oxidation, causing rancidity. Materials with high levels of poly-unsaturated fatty acids and of course, pure lipids themselves, are more prone to the development of rancidity than others. Fish meals, expeller vegetable oil cakes, and rice bran are particularly vulnerable. Grains have natural antioxidants which protect them from rapid deterioration. There are various types of chemical reactions which cause rancidity to develop. The result, as far as feed quality is concerned, is similar. Rancid fats reduce the palatability of the feed and contain toxic chemicals which may depress growth (Appendix XV). Chemicals may also be produced which reduce the availability of amino acids in the feed proteins.

Vitamin potency decreases during storage (and processing), particularly in premixes which also contain minerals. Naturally occuring vitamins in feed-stuffs also deteriorate on storage. Vitamin C is particularly susceptible, as is thiamine (vitamin B1).

7.2 Storage Procedures

7.2.1 Specific Notes
7.2.2 General Recommendations for Dry Storage - "Do's" and "Don'ts"

As shown in section 7.1., many problems can occur during feed storage. Some deterioration is inevitable. Thus ingredients should be stored for as short a period as possible and compounded feeds used quickly, expecially in tropical conditions. The method of storage depends on the type of ingredient. Some specific suggestions are given in this sub-section of the manual followed by some 'do's' and 'don'ts' on storage generally.

7.2.1 Specific Notes


Vitamins and vitamin mixes are extremely expensive ingredients and should be given special care. Their volume is usually small because their inclusion rate is low, so storage space is not normally a limiting factor. Vitamins should not be mixed with minerals before storage. Vitamins and vitamin premixes should be kept either in the manufacturer's containers or in air-tight light-proof containers. They should not be kept in hot sunny rooms. They should be kept in the coolest place available, preferably under air-conditioning. Stocks should be turned over at least every six months.

Moist and Wet Ingredients and Compounds

These materials, such as 'trash' fish, must either be used fresh (they can be iced down for up to 12 hours while stocks are being drawn from a delivery for use) or they must be kept frozen. Proper freezing of large quantities of wet materials like these requires a plate freezer and, unless you already have that kind of facility (say for the freezing of your harvested aquaculture product), freezing should be contracted out to a specialist. Once frozen, this type of ingredient can be stored in a cold store. The temperature of the cold store should not be higher than -20° C, preferably below -30° C. Rules must be established to minimize the time that the cold store door remains open and the number of times it is opened, or the product temperature will rise too high. If access to plate freezing facilities run by specialists is unavailable, small quantities of wet materials can be frozen in a cold store. Only very small quantities, though. The material must be spread into thin (1 inch) layers and the store must not be overloaded with huge quantities of unfrozen materials; it will be unable to cope. If you simply put a large drum or bag of trash fish in the cold store it will be several days before it completely freezes; rapid deteriorative changes in the feed will be taking place all that time. Moist compound feeds should be used on the day of manufacture within 2-3 hours. Don't use wet ingredients which smell of ammonia.

Dry Ingredients (Raw Materials)

See section 7.2.2.

Dry Compounded Feeds

These should be treated in the same way as dry ingredients (section 7.2.2.) but should not be stored for such a long time. Mixed feeds are more prone to damage than individual ingredients. This is because of interactions between different ingredients and because of cross contamination with insects and fungi. Mixed feeds which have undergone a heat treatment during production, such as steam pelleting, store better than other mixtures because many of the damaging factors will have been destroyed.


Keep in sealed, preferably plastic, containers, in a cool dark place. Ensure that they have had antioxidants added to them when manufactured.


No special care necessary in tropical countries but, in temperate zones, molasses may require heating in winter before this product can be used in a mixed feed.

7.2.2 General Recommendations for Dry Storage - "Do's" and "Don'ts"

For simplicity, this section of the manual has been arranged in the form of a series of instructions:

PROVIDE a building for storage which is secure and can be adequately locked. Ensure that its roof will protect the feed from rain and that surface water cannot enter the store. Provide it with ventilation points (windows are not necessary or recommended). Ventilation entry points should be low on the side facing the prevailing wind and high on the opposite side. Orient the building so that one of the long sides faces the prevailing wind. Ensure that all entry points are meshed to prevent entry by birds, rats etc. The drier and cooler you can keep this store the better your feed quality will be.

DO NOT accept deliveries of raw materials which are visibly damp or mouldy or which are obviously infested with insects.

PLAN your ingredient purchases carefully so that you do not need to keep too great a quantity in stock. Obviously you will want to store greater quantities of seasonally cheap or scarce materials but do not be tempted to buy a year's supply just because they are cheap now. It may prove very expensive indeed if half of them have to be thrown away. As a general rule, don't keep materials longer than the following guidelines:

Tropical Zone

Temperate Zone

Ground Ingredients

1-2 months

3 months

Whole Grain and Oilcakes

3-4 months

5-6 months

Compounded Dry Feeds

1-2 months

1-2 months

Vitamin Mixes (kept cool etc.)

6 months

6 months

Wet Ingredients

2-3 hours

2-3 hours

Frozen Materials

2-3 months

2-3 months

ALWAYS keep the store clean. Floors and walls should be regularly swept. Spilled material must be removed and the contents of broken bags or containers used first. Cleared areas of the store must always be cleaned before new materials are placed there.

ARRANGE your store so that new deliveries are not put in front of old stocks. The oldest materials MUST be used first.

MAKE small stacks. Large stacks of sacks lessen insect damage, which occurs mainly at the surface, but cause heat generation, with other consequential damage. In the tropics, I believe that small stacks which are used rapidly are better than large ones which remain stagnant for long periods. If possible, RAISE the sacks off the ground by stacking them on wooden pallets (platforms).

ENSURE that ingredients are clearly and indelibly labelled so that those drawing from the store are sure that they are drawing the correct ingredient (some look very similar when ground) from the oldest batch.

DON'T walk on the stacks of compounded feeds unnecessarily. This will break the pellets on the surface and lead to the production of a lot of wasteful fines (dust).

DON'T allow sacks to rest against the outer walls of the store - leave a space between the stacks and the wall.

DON'T allow staff to sleep or eat in the feed store nor, preferably, to smoke.

Further reading for section 7:

NRC (1973); NRC (1981); ADCP (1980); Lee (1981); Edwards (1978); Sedgwick (1982); Pfost and Pickering (1976); Orme (1971); Sanderude (1971); Stivers (1971).

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