PLANNING AND MANAGEMENT: TOOLS FOR ACHIEVING NUTRITIONAL EFFICIENCY IN AQUACULTURE

Brazil has great potential for aquaculture development. The availability of water resources, an extremely favorable climate and a growing demand for fish within the domestic market are all factors which have contributed to boosting this activity.

Just like any other other zootechnical and productive activity, adequate planning is fundamental for good productive yields in fish farming. Contributing to the obtainment of good profits; a main objective behind any productive activity.

Considering that approximately 60 to 80% of the total costs in aquaculture are linked to feed costs, nutritional efficiency in commercial production begins during planning. In addition, nutrition and feed management (feed rate and feed frequency) in fish are directly associated with:

Growth;

Feed conversion rate;

Water quality;

Health status;

Resistance to disease and manipulation;

Meat quality and carcass yield.

In the case of breeders, nutrition and feeding impact both the quantity of produced eggs and the quality of larvae. Thus, good feed and nutritional management are fundamental for successful commercial rearing and for profitable fish farming.

In order to obtain good nutritional efficiency, certain factors need to be taken into account. Including: the target species, its development phase, the type of production system, and the quality of feed.

The fish species which are used in aquaculture have different nutritional requirements as well as changing feeding habits (carnivorous, herbivorous or omnivorous). Knowledge regarding different characteristics such as: behavior in captivity (i.e. if they are a species that tends to live in the bottom of a body of water); positioning of the mouth and constitution of the branchial apparatus (more open or closed gill arches indicate that certain species have filtration capacities), is very valuable when establishing nutritional plans. Preventing feed waste and reducing production costs.

During the development phase, fish in their early stages – fingerlings and juveniles – have high metabolic and growth rates. Therefore, they require feed with higher protein and energy content, as well as higher feed rates, compared to those required by fish in the final fattening phase.

The adoption of adequate feed management practices in cultivated species as well as their adjustment to the type of production system, will contribute to the reduction of negative impacts. Including problems with size uniformity in the fish lot as well as poor feed conversion rates.

Typically, the number of times fish should be fed is higher in the early stages of life. During larviculture it is common for feed to be supplied five to eight times a day.During the fry phase, this frequency drops to two or three times a day, while during the fattening stage it may drop to once or twice a day. Carnivorous fish usually only feed again after digesting their previous meal Therefore, a feed supply of twice a day is enough. On the other hand, Tilapia tend to accept three meals per day.

Besides generating waste and impairing water quality, excess feeding can increase the amount of fish fat, which negatively impacts its taste. Therefore, overfeeding is detrimental for various reasons.

Fish production in Brazil is mainly carried out in semi-intensive and intensive systems. In semi-intensive systems, primary feeding of plankton (phyto and zooplankton) is usually incorporated as supplementary feeding This allows producers to reduce feed expenses. Filter fish, such as tilapia and carp, for example, are species that can make good use of this alternative type of primary feeding. In intensive production systems, fish feeding is done exclusively through commercial feed.

A careful observation of water quality and climatic conditions can contribute to optimizing feed utilization by fish. Low concentrations of dissolved oxygen and high concentrations of ammonia in the water cause appetite reductions in fish and decrease their feed utilization capacity.

When it comes to climate conditions the following fact must be taken into account. Most fish are poikilothermic, which means that they are unable to regulate their own body temperature. Therefore, when the water cools down, their metabolism slows down and when the water temperature is too high, is too high, animals suffer from heat stress. Hence, both scenarios result in lower feed intake.

The use of good quality diets is always important to obtain nutritional efficiency and obtaining the best performance from fish. Using the least amount of adequate feed which allows to maintain profits, while preserving water quality and animal welfare

Characteristics Of Good Quality Feed

High digestibility

Water stability and fluctuation

Adequate

Thus, whenever the water temperature is too low or too high, a reduction or temporary suspension of feed supply is recommended in order to avoid waste.

Good palatability

The use of low quality rations directly impairs water quality, causing stress on the fish and reducing their resistance to pathogens and disease.

It is a big mistake to think that the use of cheap feed will necessarily reduce production costs and increase profits. Considering the fact that when using poor quality feed, the producer will most likely have to use larger quantities than what he would use if he chose a product with better quality. Sometimes, even a greater feed supply does not guarantee good performance nor adequate health levels in fish fed with poor quality rations.

A correct storage of the ration is extremely important for the conservation of its nutritional characteristics. As excessive humidity, direct sunlight and contamination by microorganisms and/or insects commonly lead to considerable quality losses in the ingredients. The storage time must also be looked after, and it should not exceed 90 days.

Good planning at the time of buying the ration is always a good strategy, because the higher the purchase, the greater the chances of obtaining a better price. For this, it is necessary to check if there is enough space to store the feed as well as making sure that it will not be stored for prolonged periods of time.

The main critical points in fish nutrition include: knowledge about nutritional requirements, feed composition and feed intake. Thus, the use of adequate feed, both in quantity and quality, is fundamental for the success of fish farming.

Feed supply is another simple yet important management practice in fish production. Preferably, feed should be spread throughout the nursery, and it must not be concentrated in only one or two places. By spreading the feed, the fish farmer increases the chances for all fish to have access to it. This keeps the dominant and larger individuals from gaining greater access to the supplied feed. As it tends to occur when feed is only placed in a few spots within the tank.

An example of such success, is what occurred in a fish farm in the State of Espírito Santo, where a 40% reduction in feed conversion was achieved (from 1.6 to 1.08) through good feed planning and management. Boosting the production system, while preserving the water quality,and allowing the owner to have significant profits at the end of the production cycle.

This specific case, and the information that has been previously discussed, are all clear arguments supporting the importance of good planning and proper feed management practices in fish farming. Making them an essential tools for obtaining optimal financial results.

Planning and management: Tools for achieving nutritional efficiency in aquaculture

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