Role of Fish Nutrition and Feeding in Tropical Aquaculture Coloso14

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Note: F or Tr aining Purposes Only. Not for Publication

Role of Fish Nutrition and Feeding in Tropical Aquaculture

Relicardo M. Coloso, Ph. D.

SEAFDEC Aquaculture DepartmentTigbauan, Iloilo, Philippines

Introduction

Aquaculture continues to advance and expand to provide fish for a rapidly

growing population. It is now a well established industry worldwide and the fastest

growing food production sector. The growth in production will surely impact on the

demand for aquaculture feed as well as on key feed ingredients and exacerbate the effects

of aquaculture on the aquatic environment. Many of these effects are brought about by

the diet because feed is the biggest contributor to the total production cost. Thus, fish

nutrition and feeding of fish must be focused on improving feed composition, increasing

the efficiency of production, and decreasing the impacts on the environment by

improving nutrient retention.

Global aquaculture production of fish, crustaceans, mollusks, etc has exceeded 60

Mmt by 2012 with a value of more than 120 trillion US $. Most of this took place in

inland waters (over 40 Mmt) and the rest in marine waters (FAO 2012). If seaweed

production is added to this value, the production of all aquatic organisms would exceed

79 Mmt with a value of more than 125 trillion US $. Close to 90% of global aquaculture

production of fish, crustaceans, mollusks, etc happens in Asia, 4% each in the Americas

and Europe and 2% in Africa and Oceania.


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Recently, most of the increases in production growth have been based on the

application of aquaculture feed. At an annual growth rate of about 4-5% and about 75%

of production due to feed taking species, the feed demand exceeds 20 Mmt annually.

With an average crude protein of 30% for the aquafeed, the protein requirement will

exceed 6 Mmt per year. With fish meal being the dominant protein source for aquafeeds,

it is already evident that an industry of this size cannot continue its dependence on fish

meal. Alternative protein sources have to be required.

Feeds in aquaculture

A nutritionally balanced feed and appropriate feeding management are important

in maximizing production and profitability. Good quality feed also improves feed

conversion efficiency, lowers production costs, and reduces the impacts on the

environment. A good feeding program requires a thorough understanding of the

principles of fish nutrition and feeding. The nutrient requirements of specific fish species

for culture as well as their feeding habits and behavior and abilities to digest and utilize

food must be known.

Cultured species must be given the right amount of macro- and micronutrients,

such as proteins and essential amino acids, carbohydrates, lipids and essential fatty acids,

vitamins and minerals. Feed quality is dependent on the level of available nutrients. For

instance, the protein requirements of an herbivore like tilapia and an omnivore like

milkfish are generally lower than those of carnivores like grouper, sea bass and snapper.

Different fish species also require different amounts of essential amino acids.

Furthermore, the requirements for lipids and essential amino acids differ for those species

adapted to freshwater, brackish water or marine environments. Fish also require vitamins


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and minerals for good growth, absence of deficiency symptoms, improved resistance to

disease, and improved survival. Thus, a good understanding of the nutrient requirements

of the cultured species is needed to improve nutrient retention, feeding efficiency, and

survival.

The performance of aqua feeds is also dependent on the quality of raw materials,

reduced feed cost, and improved on-farm feeding management. The addition of

attractants, growth promoters and binders will ensure the attractability and stability of the

feed in the water. During feed preparation, nutrient composition should be maintained

and measures to reduce or eliminate the anti-nutritional factors that might be present in

the feed ingredients must be done. The quality of the feed must be maintained from

ingredient selection, feed preparation and processing, storage, and use in the farm. In

addition, a good feeding management should also be done in the farm to improve feed

performance. What to feed the fish, how much to give, when, how often and where to

feed them are important questions to answer in the exercise of good feeding practices.

Good feeding management improves nutrient retention and feed utilization and reduces

food wastage which will improve production efficiency, lower costs, and maintain the

quality of water and sediment.

Feeds and the environment

Aqua feeds have to be environment friendly. Feeds not only provide adequate

nutrition to fish, but they can also be sources of pollutants and metabolic waste products

like ammonia, urea, carbon dioxide, phosphorus, hydrogen sulfide, and organic matter

from uneaten food, feces, and colonizing bacteria. As production intensifies, the amount

of metabolic wastes in the farm also increases and eventually slows down fish growth and


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increases fish mortalities if allowed to proceed unabated. The amount of feed given

should be enough to sustain good growth and survival, minimize unconsumed feed, and

prevent the degradation of the environment which can encourage diseases, poor harvests

and huge financial losses.

Feed formulation should take into account the following factors to ensure the

sustainability of aquaculture.

1. Feeds should have a well-balanced composition. It should contain the right

amount of nutrients, a balanced protein to energy ratio as aquatic animals eat to satisfy

their energy requirements, more nutrients assimilated, and less metabolic waste output to

the surrounding environment.

2. The total phosphorus in feeds should satisfy the requirement of fish for this

mineral and should be provided by highly available forms. The control of phosphorus

excretion will result in reduced levels of phosphorus in the effluents and better pond

management.

3. The feed ingredients used should be digestible to reduce organic wastes from

feeds. Better nutrient retention and efficiency will reduce metabolic wastes.

4. Pelleted feeds should be water stable and good binders and proper pelleting

techniques should be used. Unstable pellets will result in the build up of uneaten feeds at

the pond bottom and in the rapid degradation of water and sediment quality.

5. The use of alternative protein sources to fish meal should be encouraged

through continuous research and development.


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6. The levels of anti-nutritional factors in feed ingredients should be minimized

through proper ingredient choice and processing methods to minimize or eliminate these

factors in the finished feed. The finished feeds should be properly stored to eliminate the

growth of fungi, molds and other organisms which contain mycotoxins that can degrade

feed quality in storage and become toxic to fish and consumers.

Feeds and sustainable aquaculture

Research and development on feeds is absolutely necessary in making aquaculture

sustainable for future generations. Much has been achieved in the last forty years in

terms of progress in feed formulation for many tropical species of fish and crustaceans,

but there are still a lot that we do not know in the nutrition and feeding of tropical fish,

crustaceans, mollusks and other aquatic organisms. R & D in aqua feeds has been a

priority but we still have a lot to do to achieve the goals of sustainable aquaculture.

1. Alternatives to fish meal and fish oil have to be found. Global fish meal supply

is limited at 5 Mmt and fish oil at 1 Mmt tons. Aquaculture is already using about 70%

of the supplies. For aquaculture to be sustainable, its dependence on fish meal and fish

oil has to be reduced. We have already been successful in bringing down the level of fish

meal in fish diets but more has to be done. Agricultural by-products such as vegetable

and animal meals should be used to produce cheap and cost effective diets for

aquaculture. Many agricultural by products such as meat meals, poultry offals and

feather meals, legumes such as beans and peas, wheat gluten, and other grains are

potential fish meal replacements. The use of fish meal should be reserved for use in

specialized feeds such as larval feeds and for the development of aqua feeds for emerging

species. In addition, replacements for fish oils have to be found and making diets with


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optimal lipid and fatty acid profiles will be needed. Biotechnology can contribute novel

products and ingredients to produce aqua feeds with desirable nutrient profiles and are

cost effective.

2. Feed cost has to be reduced. As feed is the most expensive item in fish farming,

the availability of a cost effective feed is a bottle neck in aquaculture. Feed formulations

have to be refined to make them cheaper by using locally available ingredients. Because

the availability of raw materials differ from one country to another, the location,

availability, nutrient composition, and cost of these resources have to be known so that

cost-effective feeds can be formulated.

3. The natural productivity of ponds and other systems have to be maximized so

that the feeds for many aquaculture species in the tropics can be used only as a

supplement to the natural food. Feeds are often expensive because they are complete diets

for the intended species, but supplementary feeding practices for systems that are able to

increase natural productivity should be encouraged to lessen the dependence of fish

farming on artificial feeds.

4. Feeds that are environment friendly should be developed and used with

efficient feeding management to minimize the environmental impacts of aquaculture.

Environment friendly feeds require the use of renewable ingredients and modern

extrusion technologies to produce healthy and consumer safe products. Balanced feeds

with good nutrient retention, stability and efficiency should be developed and used

together with efficient feeding strategies to increase production, profitability, and

sustainability. These innovations require the expanded research support of both public

and private sectors to make the aquaculture industry sustainable for future generations.


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Suggested References:

FAO 2012. FAO yearbook. Fishery and Aquaculture Statistics. 2010/FAO annuaire.

Statistiques des peches et de laquaculture. 2010/FAO anuario. Estadisticas de

pesca y acuicultura. 2010. Rome/Roma, FAO. 78 pp.

Millamena, O. M., Coloso, R. M., Pascual, F. P. (eds). 2002. Nutrition in Tropical

Aquaculture. Essentials of fish nutrition, feeds, and feeding of tropical aquatic

species. SEAFDEC Aquaculture Department, Tigbauan, Iloilo, Philippines. 244

pp.

Role of Fish Nutrition and Feeding in Tropical Aquaculture Coloso14

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