INTRODUCTION

Nutrient

Types of Nutrients

Some basic idea of Carbohydrate

Classification of carbohydrate

DIGESTION OF CARBOHYDRATE IN FISH

Types of carbohydrate utilize by fish

Carbohydrates and fish

Factors affecting carbohydrate digestibility in fish

Advantages of utilizing carbohydrate in fish feed

Disadvantages of utilizing carbohydrate in fish feed

Carbohydrate percentage in some fish feed

Summary

Conclusion

References

Nutrition: Nutrition is the sum total of the processes involved in the taking in and the utilization of food substances in the body.It involves ingestion, digestion,absorption and

assimilation.

Feeds contain nutrients & the energy essential for :(1) The growth,(2) Reproduction & (3) Repair and maintenance of the body.

For Proper nutrition we need feed, containing proper nutrients.

• A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment.

• They are used to build and repair tissues, regulate body processes and are converted to and used as energy.

• A feed containing all nutrients in sufficient amount is considered as good feed.

Types of Nutrients

• There are 6 types of nutrients. Such as-i) Carbohydrate iv) Vitaminii) Protein v) Mineraliii) Fat vi) Water

• Depending on the use in nutrition Nutrients are of 2 type. Such as-

a) Macro Nutrientb) Micro Nutrient

• As the role of carbohydrate, protein, & Fat in nutrition is more, these are considered as macro nutrients.

• The role of vitamin, mineral, & water in nutrition is quite less. So, they are considered as micro nutrient. But these are essential for nutrition.

• A carbohydrate is an organic compound that is composed of atoms of carbon, hydrogen and oxygen in a ratio of 1 carbon atom, 2 hydrogen atoms, and 1 oxygen atom.

• The common formula of carbohydrate is Cn(H2O)n

• The primary function of carbohydrates is for short-term energy storage (sugars are for Energy). A secondary function is intermediate-term energy storage (as in starch for plants and glycogen for animals). Other carbohydrates are involved as structural components in cells, such as cellulose which is found in the cell walls of plants.

• Enzymes for carbohydrate digestion are apparently present in fish. The enzymes for the major carbohydrate metabolic pathways, such as glycolysis, tricarboxylic acid cycle, pentose phosphate shunt, gluconeogenesis, and glycogen synthesis, have been demonstrated (Shimeno, 1974).

• Even though the various enzymes and pathways for glucose metabolism have been detected, the role of dietary carbohydrates and the contribution of glucose to the total energy requirement of fish remain unclear.

The relative use of dietary carbohydrates by fish varies and appears to be associated with the complexity of the carbohydrate. Fish can better utilize mono- or di- saccaridethan polysaccaride. Such as, Glucose, maltose, and sucrose resulted in the best growth rates, followed in descending order by dextrin, potato starch, and glucosamine when various carbohydrate sources were fed to young chinook salmon at a concentration of 10 percent of the diet (Buhler and Halver, 1961).

Carbohydrates make up 20-30% of the common commercial foods. While they are alternate sources of energy, they are not very necessary for fish growth. Though most fish will handle some amount of carbohydrates, they develop signs of ill health if there is a high concentration of carbohydrate in their diet. For instance, if young fish ingest too much of carbs, other nutrients will not be absorbed appropriately by their bodies. That is why cereal grains, which have very high levels of raw starch, are not ingested fully by fish.

There are some factors that affect the digestibility of carbohydrate. They are-• Feeding Habits of fish.• Age of fish.• The availability of carbohydrate

enzymes.• The anatomy of the digestive tract of

fish.• The size of carbohydrate molecule.

• The nutritional value of carbohydrates varies among fish.

• Tropical-water fish can use much greater amounts of dietary carbohydrate than cold-water and marine fish.

• In general, carnivorous fish such as salmoids digest carbohydrates less efficiently than omnivorous and herbivorous fish .

• The poor ability to utilize carbohydrates applies also to all the carnivorous fishes.

• Due to high enzyme activity certain carp species such as common carp (Cyprinus carpio) & grass carp (Ctenopharyngodon idella) utilize carbohydrates well.

• while fry respond negatively.

• Various catfish species use carbohydrates even at levels of almost 50%.the african tilapia utiliseddietary carbohydrates satisfactorily.

• carbohydrate is the least expensive source of dietary energy, the maximum tolerable concentration should be used with regard to the fish species.

• fish can only extract about 1.6 kcal from 1 gram of carbohydrate.

• Carbohydrates may serve as precursors for the dispensable amino acids, lipids and nucleic acids, which are metabolic intermediates necessary for fish growth.

• Starch is also important for the binding properties of extruded and pelleted feeds.

• In shrimp carbohydrate are important as energy source for chitin synthesis and synthesis of non-essential fatty acids. However, there are different in utilization of the carbohydrate source. Monosaccharaides such as glucose, galactose and fructose inhibit the growth of brown shrimp(Penaeusaztecus), kuruma shrimp(Penaeus japonicus).

• Chitin is a linear polysaccharide and the major component of exoskeleton of shrimp. Due to molting this has to be steadily replaced. It is synthesized from glucose via glucomine, a precursor of chitin.

• In fish, carbohydrates are stored as glycogen that can be mobilized to satisfy energy demands.

• The growth rate of channel catfish fingerlings was greater when their diets contained some carbohydrates rather than only lipids for all the non protein energy (Garling and Wilson, 1977).

• The most likely symptom of oversupply of carbohydrates in carp diets is excessive deposition of fat in the liver, heart and carcass.

The most likely symptom of oversupply of

carbohydrates in carp diets is excessive

deposition of fat in the liver, heart and

carcass.

Fatty liver in fish

Carbohydrate percentage in some fish feed

Fish Feed Carbohydrate(%)

Groundnut oilcake 6-7

Soybean Meal 4-5

Rice polish 7-10

Rice bran 8-12

Deoiled rice bran 10-15

Rapeseed cake 11-15

Salseed Cake 10-13

Cont….

Fish feed Carbohydrate(%)

Til oilcake 10-15

Mustard oilcake 10-16

Cotton seed cake 12-16

Sunflower oilcake 15-18

Copra cake 12-17

Maize flour 2-3

Barley grains 4-6

Cont…

Fish feed Carbohydrate(%)

Wheat flour 1-4

Like proteins & lipids, Carbohydrate are also another source of energy. Fish do not have specific dietary requirement. But Carbohydrates (starches and sugars) are the most economical and inexpensive sources of energy for fish diets. Although not essential, carbohydrates are included in aquaculture diets to reduce feed costs and for their binding activity during feed manufacturing. Dietary starches are useful in the extrusion manufacture of floating feeds.

Cooking starch during the extrusion process makes it more biologically available to fish.

In fish, carbohydrates are stored as glycogen that can be mobilized to satisfy energy demands. They are a major energy source for mammals, but are not used efficiently by fish. For example, mammals can extract about 4 kcal of energy from 1 gram of carbohydrate, whereas fish can only extract about 1.6 kcal from the same amount of carbohydrate.

CONCLUSION

Fish do not have specific dietary requirement. Tropical-water fish

can use much greater amounts of dietary carbohydrate than cold-

water and marine fish. Carbohydrates make up 20-30% of the

common commercial foods. As carbohydrate is the least expensive

source of dietary energy. Carbohydrates may serve as precursors for

the dispensable amino acids, lipids and nucleic acids, which are

metabolic intermediates necessary for fish growth. Carbohydrate is

also important for the binding properties of feeds.

Hand book of Fisheries and Aquaculture-ICAR- S. AYYAPPAN.

Hand book on Ingredients for Aquaculture Feeds- Joachim W. Hertrampf and FelicitasPiedad-Pascual

An Introduction to fishes- S.S.Khanna

www.fao.org

www.wikipedia.org

Pictures are collected from www.google.com