Proper aquafeed management practices, including transport, handling, and storage practices, are essential to any profitable aquaculture farm.

These practices are essential to help maintain nutrient quality from feed supplier to pond in order to prevent wastage in the form of spoilage or physical damage, which can be costly to the fish farmer. Apart from physical feed wastage, spoilt feed can impair growth performance, reduce water quality, increase disease susceptibility, and subsequently cause mortalities.

The main causes of feed deterioration are either physical or biological damage.

Physical damage includes:

Transport and handling: Physical damage can be caused from a variety of factors. Transporting feeds over long distances for extended periods, in open trucks, motorbikes or bicycles, can result in long transit times and, on poor roads, results in pellet damage. This can lead to a concomitant generation in fines and dust.

Additionally, the compression and abrasion of pellets caused by excessive or rough handling can lead to pellet damage and increased levels of dust. High levels of dust in feed can lead to a decrease in water quality and will represent an economic loss to the farmer. Moreover, damaged feeds expose the nutrients to microbial action.

Temperature and sunlight: Direct sunlight or extreme heat can damage sensitive nutrients and cause a reduction to the nutritional value of the feed. Moreover, temperature fluctuations can lead to condensation and free moisture formation. Moisture accompanied with relatively high temperatures will promote fungal, bacterial and insect growth.

Moisture: Excess  feed moisture as well as relatively high humidity levels will promote the growth of fungi and insects. It can increase the rate of oxidation and subsequently the rate of spoilage. One of the causes for feed to increase in moisture is condensation. When feed bags are left in contact with the ground or wall, condensation will form and seep into the bags.

In addition, extruded aquafeeds are more porous than pelleted feeds, which increases the moisture absorption in feeds. On top of that, aquaculture environments are generally high humidity areas, especially when working with warm water species. These factors combined can significantly increase the moisture content in aquafeeds if proper care is not taken.

Insect and rodent infestation: Insects and rodents consume feed and destroy containers, causing feed wastage and economic losses. Moreover, they can introduce bacteria into feeds through their faeces, which leads to feed spoilage.

Biological damage includes:

Microbial spoilage: Bacteria, under the right conditions, will rapidly multiply and break down feed to produce acids and waste products. These, in combination with bacteria, can cause harm to fish. In addition, food borne pathogens influence both fish and humans.

For instance, salmonella impairs the quality of proteins and lipids, and produces toxins. Salmonella is a zoonotic bacterium that can be transferred between fish and humans when handled or consumed. Bacteria are not the only microbes that affect feeds. The growth of fungi or mould can damage feed and produce health damaging mycotoxins that, when fed to fish, can cause a decrease in growth performance and overall health.

Oxidation: Oxidation reactions occur in the presence of oxygen which causes feed to spoil at a quicker rate. For instance, fat in feeds and feedstuffs can form peroxides that cause rancidity and off-flavours. These peroxides may bind with proteins or vitamins and reduce their availability. To compound this, aquafeeds are often high in fats, which are more susceptible to oxidation.

To prevent or minimise the deterioration of feeds, the following important guidelines should be applied:

• Store dry feeds for no longer than three months. Use old feeds before the new deliveries or batches. The first in, first out practice should be applied.

• Do not walk on the feed bags or use excessive force when handling them.

• Provide a clean, cool, dry, secure, and well-ventilated storage area, such as storage sheds. Feeds that accumulate high moisture levels (≥ 13%) cause insects and moulds to become active at high temperatures. Temperatures below 15o C will reduce or retard insect growth.

• Place feed bags out of direct sunlight. Exposure to sunlight and high temperatures will damage ingredients such as essential vitamins.

• Feed bags should not be piled more than 10 bags high on a platform 12 to 15 cm off the floor. Too much weight on the bags can cause physical damage to the feed.

• Short-term storage bins should be placed under shade cloth in sealed bins. The bins should be sealed when not in use. Sealed bins limit oxygen supply for oxidation and reduces the quantity of moisture that the feed is exposed to.

• To discourage insects infestation, the application or dusting of nontoxic diatomaceous earth around and under the pallets can form part of the feed storage management programme.

• Disinfect the storage room and feed equipment regularly. This involves the physical or chemical disinfection of microbes that may contaminate feeds.

• Fumigate the feed storeroom to ensure that there are no insects or pests.

A fumigant is a chemical which can exist in the gaseous state in a sufficient concentration to be lethal to a given pest organism. In conclusion, all the efforts made to produce and store feed is a team effort between farmer and producer. Against this background, the shelf-life claimed by the producers can be affected by onfarm storage techniques.

For further information regarding feed storage and handling, please contact Novatek Animal Feeds at fish.ta@novatek.co.zm.