Bureau and Cho 1999 Introduction to Nutrition and Feeding of Fish

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Bureau, D.P. and C.Y. Cho. 1999. Nutrition and feeding of fish. OMNR Fish Culture Course, Unversity of Guelph,

Guelph, Ontario, 21-25 June 1999.

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An Introduction to

Nutrition and Feeding of Fish

Dominique P. Bureau and C.Young Cho

Fish Nutrition Research Laboratory

Dept. of Animal and Poultry ScienceUniversity of Guelph, Guelph, Ontario, N1G 2W1, Canada

email: [email protected]

In culturing fish in captivity, nothing is more important than sound nutrition and adequate

feeding. If the feed is not consumed by the fish or if the fish are unable to utilize the feed

because of some nutrient deficiency, then there will be no growth. An undernourished animal

cannot maintain its health and be productive, regardless of the quality of its environment.

The production of nutritionally balanced diets for fish requires efforts in research, quality

control, and biological evaluation. Faulty nutrition obviously impairs fish productivity andresults in a deterioration of health until recognisable diseases ensues. The borderlines between

reduced growth and diminished health, on the one hand, and overt disease, on the other, are very

difficult to define. There is no doubt that as our knowledge advances, the nature of the

departures from normality will be more easily explained and corrected. However, the problem of

recognizing a deterioration of performance in its initial stages and taking corrective action will

remain an essential part of the skill of the fish culturist.

1. Protein and Amino Acid Requirements of Fish

Protein

Protein is required in the diet to provide indispensable amino acids and nitrogen for

synthesis of non-indispensable amino acids. Protein in body tissues incorporate about 23 amino

acids and among these, 10 amino acids must be supplied in the diet since fish cannot synthesise

them. Amino acids are need for maintenance, growth, reproduction and repletion of tissues. A

large proportion of the amino acid consumed by a fish are catabolized for energy and fish are

well-adapted to using an excess protein this way. Catabolism of protein leads to the release of

ammonia.

Protein is the most important component of the diet of fish because protein intake

generally determines growth (protein growth has, in general, priority), has a high cost per unit

and high levels are required per unit of feeds.

First observations on fish protein and amino acid requirements came from studies on

natural diet of different fish. Natural diet (plankton, invertebrates, fish) is generally rich in

protein and has a good amino acid balance. All dietary proteins are not identical in their


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nutritive value. The nutritional value of a protein source is a function of its digestibility and

amino acid makeup. A deficiency of indispensable amino acid creates poor utilization of dietary

protein and hence growth retardation, poor live weight gain, and feed efficiency. In sever cases,

deficiency reduces the ability to resist diseases and lowers the effectiveness of the immune

response mechanism. For example, experiments have shown that tryptophan-deficient fish

become scoliotic, showing curvature of the spine, and methionine deficiency produces lenscataracts. Salmonid diets generally contain 35-45% digestible protein (DP), or 40-50% crude

protein. However, amino acids or protein must be supplied in relation to digestible energy (DE).

The recommended ratio of protein to energy in the salmonid diet is 20-26 g DP/MJ DE (92-102 g

protein per Mcal). Increasing these proportions increases ammonia excretion; the requirement for

dissolved oxygen is also increased because the efficiency with which the energy is used is

decreased.

Why do fish have such high requirements for protein? The main factors explain this

phenomenon:

1) The protein requirement in terms of dietary concentration (% of diet) is high but

the absolute requirement isnt (g/kg body weight gain). This is due to the fact that

fish have a lower absolute energy requirement than mammals. This results in

similar g body weight gain/g protein ingested as mammal but better feed

efficiency (gain:feed).

2) Protein (amino acids) is used as a major energy source. Some economy can be

made here if other dietary fuel are present in adequate amounts, e.g. increasing

the lipid (fat) content of diet can help reduce dietary protein (amino acid)

catabolism and requirement. This is referred to as protein-sparing effect of lipids.Protein to useful energy ratio is the factor that should be considered, not %

protein of the diet per se.

Indispensable amino acid requirements

10 Indispensable amino acids

Phenylalanine (Phe) Histidine (His) Isoleucine (Iso) Leucine (Leu)Lysine (Lys) Methionine (Met) Tryptophan (Trp) Valine (Val)

Arginine (Arg) Threonine (Thr)


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Table 1. Indispensable amino acid requirements of different species of teleost (g / 100 g protein)

Amino

acids

Salmonid Catfish Carp Tilapia Milkfish Sea

Bream

Sea

Bass

Arg 4.2 4.3 4.4 4.1 5.6

His 1.6 1.5 2.4 1.7 2.0

Ile 2.0 2.6 3.0 3.1 4.0

Leu 3.6 3.5 4.7 3.4 5.1

Lys 4.8 5.0 6.0 4.6 4.0 5.0 4.8

Thr 2.0 2.1 4.2 3.8 4.9

Trp 0.6 0.5 0.8 1.0 0.6 0.6

Val 2.2 3.0 4.1 2.8 3.0

Met+Cys 2.4 2.3 3.5 3.2 4.8 4.0 4.4

Phe+Tyr 5.3 4.8 8.2 5.6 5.2

Table 2. Amino acid composition of common protein sources (g/ 100 g protein).

CP Met Lys Trp Thr Ile His Val Leu Arg Phe(+Cys) (+Tyr)

Requirement 1.7 4.8 0.6 2.0 2.0 1.6 2.2 3.6 4.2 2.7

(2.4) (5.3)

Fish meal 68 3.1 7.9 1.1 4.0 4.2 8.8 7.9 7.1 8.3 3.6

Soybean meal 48 1.6 6.7 1.3 4.2 5.5 2.7 5.7 8.0 8.0 5.7

Corn gluten meal 60 3.2 1.7 0.5 3.3 3.8 2.0 4.5 15.7 3.2 6.3

Blood meal 85 1.2 6.3 1.2 4.5 0.9 3.6 6.1 12.2 2.8 6.0

Meat and bone

meal

50 1.2 4.9 0.4 4.0 3.8 3.3 5.3 5.7 6.0 4.0

Poultry by-product

meal

65 1.7 5.9 0.9 4.0 2.9 2.2 4.8 5.7 7.5 2.5

Feather meal 85 0.7 1.2 0.5 3.3 3.1 0.3 5.4 9.2 4.6 3.1


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2. Lipids (Fats)

Lipids (fats) encompass a large variety of compounds. Lipids have many roles: energy

supply, structure, precursors to many reactive substances, etc. In the diet or carcass of fish,

lipids are most commonly found as triglycerides, phospholipids and, sometimes, wax esters.Triglycerides are composed of a glycerol molecule to which three fatty acids are attached.

Phospholipids are also composed of a glycerol molecule but with only two fatty acids. Instead of

a third fatty acid a phosphoric acid and another type of molecule (choline, inositol, etc.) are

attached. Wax esters are made of a fatty acid and a long chain alcohol and are a common form

of lipid storage in certain species zooplankton . The main role of triglycerides is in the storage of

lipids (fatty acids). Phospholipids are responsible for the structure of cell membranes (lipid bi-

layer). Fatty acids are the main active components of dietary lipids. Fish are unable to

synthesize fatty acids with unsaturation in the n-3 or n-6 positions yet these types of fatty acids

are essential for many functions. These two types of fatty acids are, therefore, essential for the

animal and must be supplied in the diet.

Deficiency in essential fatty acid result in general, in reduction of growth and a number

of deficiency signs, including depigmentation, fin erosion, cardiac myopathy, fatty infiltration of

liver, and shock syndrome (loss of consciousness for a few seconds following an acute stress).

Salmonids require about 0.5 to 1% long chain polyunsaturated n-3 fatty acids (EPA (20:5 n-3)

and DHA (22:6 n-3)) in their diet. This amount is easily covered by ingredients of marine

origins, such as fish meal and fish oil, which are always present in significant amounts in

salmonid feeds.

3. Carbohydrates

Carbohydrates represent a very large variety of molecules. The carbohydrate most

commonly found in fish feed is starch, a polymer of glucose. Salmonid and many other fish

have a poor ability to utilize carbohydrates. Raw starch in grain and other plant products is

generally poorly digested by fish. Cooking of the starch during pelleting or extrusion, however,

greatly improves its digestibility for fish. However, even if the starch is digestible, fish only

appear to be able to utilize a small amount effectively. Carbohydrates only represent a minor

source of energy for fish. A certain amount of starch or other carbohydrates (e.g. lactose,

hemicellulose) is, nevertheless, required to achieved proper physical characteristic of the feed.


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4. Vitamins

The vitamins are generally defined as dietary essential organic compounds, required only

in minute amounts, and which play a catalytic role and but no major structural role. So far, 4 fat-

soluble and 11 water-soluble vitamins or vitamin-like compounds have been shown to beessential to fish. Requirement is generally measured in young fast growing fish. However,

requirements may depend on the intake of other nutrients, size of the fish, and environmental

stress. The recommended levels and the deficiency signs are summarized in Tables 3 and 4.

Many symptoms of vitamin deficiency are non-specific. It is also tedious and expensive to

analyze diets for vitamins. Therefore, diagnostic of vitamin deficiencies is often difficult.

Nutritional disorders caused by vitamin deficiencies can impair utilization of other nutrients,

impair the health of fish, and finally lead to disease or deformities. Nutritional deficiencies signs

usually develop gradually, not spontaneously. However, the culturist may obtain clues of

deficiency indirectly through low feed intake and poor live weight and feed efficiency.

Table 3. Vitamin requirement of salmonids.

Vitamin Requirement

Fat-soluble vitamins

Vitamin A, IU/kg 2,500

Vitamin D, IU/kg 2,400

Vitamin E, IU/kg 50

Vitamin K, mg/kg 1

Water-soluble vitamin, mg/kg

Riboflavin 4

Pantothenic acid 20

Niacin 10

Vitamin B12 0.01

Biotin 0.15

Folate 1.0

Thiamin 1

Vitamin B6 3

Vitamin C 50

Vitamin-like compounds, mg/kg

Choline 1,000

myo-Inositol 300


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Table 4. Deficiency signs associated with various nutrients.

Deficiency Sign Nutrient

Anemia Folic Acid, Inositol, Niacin, Pyrodoxine, Rancid Fat

Riboflavin, Vitamin B12, Vitamin C, Vitamin E

Vitamin K

Anorexia Biotin, Folic Acid, Inositol, Niacin, Pantothenic Acid

Pyrodoxine, Riboflavin, Thiamin, Vitamin A

Vitamin B12, Vitamin C

Acites Vitamin A, Vitamin C, Vitamin E

Ataxia Pyrodoxine, Pantothenic acid, Riboflavin

Atrophy of Gills Pantothenic Acid

Atrophy of Muscle Biotin, Thiamin

Caclinosis : renal Magnesium

Cartilage abnormality Vitamin C, Tryptophan

Cataracts Methionine, Riboflavin, Thiamin, Zinc

Ceroid liver Rancid Fat, Vitamin E

Cloudy lens Methionine, Riboflavin, Zinc

Clubbed gills Pantothenic Acid

Clotting blood: slow Vitamin K

Colouration: dark skin Biotin, Folic Acid, Pyrodoxine Riboflavin

Convulsions Biotin, Pyrodoxine, Thiamin

Discolouration of skin Fatty Acids, Thiamin

Deformations: bone Phosphorous

Deformations: lens Vitamin A

Degeneration of gills Biotin

Dermatitis Pantothenic Acid

Diathesis, exudative Selenium

Distended stomach Inositol

Distended swimbladder Pantothenic Acid

Dystrophy, muscular Selenium, Vitamin E


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Table 4. Continued


Edema Niacin, Pyrodoxine, Thiamin, Vitamin A, Vitamin E

Epicarditis Vitamin E

Equilibrium loss Pyrodoxine, Thiamin

Erosion of fin Fatty Acids, Riboflavin, Vitamin A, Zinc

Exophthalmos Pyrodoxine, Vitamin A, Vitamin C, Vitamin E

Exudated gills Pantothenic Acid

Fatty liver Biotin, Choline, Fatty Acids, Inositol, Vitamin E

Feed efficiency: poor Biotin, Calcium, Choline, Energy, Fat, Folic Acid,

Inositol, Niacin, Protein, Riboflavin

Fragility: erythrocytes Biotin, Vitamin B12, Vitamin E

Fragility: fin Folic Acid

Fragmentation of erythrocytes Biotin, Vitamin B12, Vitamin E

Gasping, rapid Pyrodoxine

Goitre Iodine

Growth, poor Biotin, Calcium, Choline, Energy, Fat, Folic AcidInositol, Niacin, Pantothenic Acid, Protein, Pyrodoxine

Riboflavin, Thiamin, Vitamin A, Vitamin B12

Vitamin C, Vitamin E

Hematocrit, reduced Iron, Vitamin C, Vitamin E

Hemoglobin, low Iron, Vitamin B12, Vitamin C

Hemorrhage: eye Riboflavin, Vitamin A

Hemorrhage: gill Vitamin C

Hemorrhage: kidney Choline, Vitamin A, Vitamin C

Hemorrhage: liver Vitamin C

Hemorrhage: skin Niacin, Pantothenic Acid, Riboflavin, Vitamin A, Vitamin C

Irritability Fatty Acids, Pyrodoxin, Thiamin


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Table 4. Continued


Lesion: colon Biotin, Niacin

Lesion: eye Methionine, Riboflavin, Vitamin A, Vitamin C, Zinc

Lesion: skin Biotin, Inositol, Niacin, Pantothenic Acid

Lethargy Folic Acid, Niacin, Pantothenic acid, Thiamin

Lipoid liver Fatty Acids, Rancid fat

Lordosis Vitamin C

Myopathy, cardiac Essential Fatty Acids

Necrosis : liver Pantothenic Acid

Nerve disorder Pyrodoxine, Thiamin

Pale liver (glycogen accumulation) High Digestible Carbohydrate, Biotin

Photophobia Niacin, Riboflavin

Pinhead Starvation

Pigmentation, iris Riboflavin

Prostration Pantothenic Acid, Vitamin C

Rigor mortis, rapid Pyrodoxine

Scoliosis Phosphorus, Tryptophan, Vitamin C, Vitamin D

Shock syndrome Essential Fatty Acids

Slime, blue Biotin, Pyrodoxine

Spasm, muscle Niacin

Swimming, erratic Pyrodoxine

Swimming, upside down Pantothenic Acid

Tetany, white muscle Niacin, Vitamin D

Vascularization, cornea Riboflavin


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5. Minerals

Inorganic elements (minerals) are required by fish for various functions in metabolism

and osmoregulation. Fish obtain minerals from their diet but also from their environment. Many

minerals are required in trace amounts and are present in sufficient quantity in the surroundingwater for the fish to absorb through their gills. In freshwater, there is generally sufficient

concentration of calcium, sodium, potassium and chloride for the fish to absorb and cover its

requirements. The totality of the requirement for other minerals must, in general, be covered by

the diet. Dietary minerals play many roles. There generally have a structural (e.g. bone

formation) or catalytic (e.g. metalloenzyme) role. Minerals required by fish included calcium,

phosphorus, sodium, potassium, magnesium, iron, copper, zinc, cobalt, selenium, iodine, and

fluorine. The recommended levels of minerals in the diet are shown in Table 5. There are

numerous deficiency signs and some are highlighted in Table 4. Reduced growth, feed

efficiency and skeletal deformities is the most common signs of mineral deficiencies.

Table 5. Mineral requirement of salmonid fish in freshwater.

Mineral Requirement (mg/kg feed)*

Calcium (Ca) 10,000

Chlorine (Cl) 9,000

Potassium (K) 7,000

Sodium (Na) 6,000Phosphorus (P) 6,000

Magnesium (Mg) 500

Iron (Fe) 60

Zinc (ZN) 30

Manganese (MN) 13

Copper (Cu) 3

Iodine (I) 1.1

Selenium (Se) 0.3

* Requirement in the absence of significant amounts of the specific mineral in the water.


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6. Digestion

Digestive tract anatomy and physiology

Digestive system of fish is, in general, relatively simple compared to digestive system ofbirds and mammals but there are numerous similarities.

Structure Characteristics

Barbel taste buds

Mouth teeth, no chewing, taste buds

Pharynx pharyngeal teeth (calcified structures)

Oesophagus short, thick, taste buds, gizzard

Stomach present or absent, acid, enzymes, rate of digestion correlates with

mass of food remaining in stomach, emptying is affected by

temperature.

Anterior intestine secretive and absorptive epithelial cells, no villi but numerous

folds present, microvilli present, enterocytes with brush border

membrane

Pyloric caeca present in some case, variable # between species and individuals(rainbow trout 50-200 p.c.). Increase absorptive surface, number

apparently shows weak correlation with digestibility and growth.

Ratio intestine/fork length = 0.7, ratio intestine + p.c./fork length =

3.9

Pancreas Generally a diffuse tissue, except for eel, pike, flat fish

Hindgut Not really morphologically distinct from anterior intestine but cell

type changes. Squamous epithelial cells, mucus production, highly

vacuolated cells, absorption of macromolecules by pinocytosis

(tissue reabsorb proteins (enzymes) for recycling).


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Figure 1 Various digestive configurations

Reference : Smith, L.S. 1989. pp.331-421. In:Halver, J.E. (Ed.). Fish Nutrition. 2nd Edition.

Academic Press, San Diego. 798p.

The Figure 1 show that anatomy of the gastrointestinal tract differs quite significantly

between species, especially between species with difference feeding habits. Difference in total

enzymes activity between species are not very pronounced for proteases and lipases but difference

are rather significant for carbohydrases.


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Estimates of apparent digestibility for salmonids

Table 6 presents the apparent digestibility coefficients for commonly used ingredients in

salmonid feeds as measured by Cho et al. (1982). Fish have different digestive capabilities

compared to terrestrial animals, and many feedstuffs, particularly cereal grains and their by-products

which contain high levels of starch and fiber, are very poorly digested by carnivorous fish. Theapparent digestibility of good quality protein by fish is very high. However, several factors can

affect the digestibility of protein. The type of drying technique used during processing is a very

important factors. A good demonstration of this is seen in blood meal. The protein digestibility of

flame-dried blood meal is very low whereas the digestibility of spray-dried blood meal is very high.

The same phenomenon can occur with fish meal.

Table 6. Apparent digestibility coefficients of ingredients measured with rainbow trout.

Apparent digestibility coefficients (%)

Ingredients Dry

Matter

Crude

Protein

Lipid Energy

Alfalfa meal 39 87 71 43

Blood meal

ring-dried 87 85 - 86

spray-dried 91 96 - 92

flame-dried 55 16 - 50

Brewers dried yeast 76 91 - 77

Corn yellow 23 95 - 39

Corn gluten feed 23 92 29Corn gluten meal 80 96 - 83

Corn distiller dried soluble 46 85 71 51

Feather meal 77 77 - 77

Fish meal, herring 85 92 97 91

Meat and bone meal 70 85 - 80

Poultry by-products meal 76 89 - 82

Rapeseed meal 35 77 - 45

Soybean, full-fat, cook. 78 96 94 85

Soybean meal, dehulled 74 96 - 75

Wheat middlings 35 92 - 46

Whey, dehydrated 97 96 - 94Fish protein concentrate 90 95 - 94

Soy protein concentrate 77 97 - 84


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7. Feed Formulation and Manufacturing

Diet formulation

Diet formulation and preparation are the process of combining feed ingredients to form a

mixture that will meet the specific goals of production. It is often a compromise between theideal formula and practical considerations. The primary objectives are to produce a mixture that

(is) :

Nutritionally balanced (to support maintenance, growth, reproduction, health)

Economical Palatable

Water stable Minimizes waste output & effect on water quality

Produces desirable final product (attractive & safe)

Practical considerations :

Ingredients price and availability Anti-nutritional factors

Pelletability of mixture Storage and handling requirements

Table 7. Composition of the grower formulae used by the OMNR Fish Culture Stations over the

past 10 years.

Formulae

Ingredients MNR89G MNR91H MNR95HG MNR98HG

%

Fish meal, herring, 68% CP 20 35 18 18

Blood meal, spray-dried, 80%CP

9 9 - -

Corn gluten meal, 60% CP 17 15 49 37.6

Soybean meal, 48% CP 12 14 - -

Poultry meal, 68% CP - - - 13

Brewers dried yeast, 45% CP - - 6 -

Wheat middlings, 17% CP 20 - - -

Whey, 12% CP 8 10 11 9

Vitamin premix 0.5 0.5 1 0.5

Mineral premix 0.5 0.5 1 0.5

L-Lysine - - - 1.4

Fish oil 13 16 14 20

Digestible Composition

Digestible protein, % 37 44 44 42

Digestible energy, MJ/kg 17 20 20 21

DP/DE, g/MJ 22 22 22 20


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Ingredient Quality

The first consideration for formulation and production of successful diets is the quality of

the feed ingredients. Diets produced with poor quality raw materials and under adverse

processing conditions have inferior nutritive value and adverse effects on fish health. Quality

criteria for the ingredients must be respected to insure that the final product is of consistent

quality and that deleterious effects are avoided. The chemical composition (nutrient, energy,

antinutrients, contaminants) of the ingredient obviously plays a determinant role the quality.

However, biological aspects, such as digestibility and utilization of nutrients are most important

and often overlooked.

The loss of indigestible matter from the diet as feces is the primary reason for variation in the

nutritional value of feed ingredients. Measurement of digestibility provides, in general, a goodindication of the availability of energy and nutrients, thus providing a rational basis upon which diets

can be formulated to meet specific standards of available nutrient levels. Several factors can affect

the digestibility of protein or specific amino acids. The type of drying techniques used during

processing, the composition of the protein fraction are the factors which have a determinant

effect on the digestibility of protein of a feed ingredients.

Fishery by-products:

There are various qualities of fish meals on the market, relating to the original raw fish

quality, level of ash in the meals, and the type of processing techniques used. The most important

factor is the freshness of the product. Fish must be processed as soon as possible after capture.

Ageing and spoilage decrease the nutritive value and also lead to the contamination with

potential toxic compounds, such as histamine, cadaverine, and agmatine. The second most

important factor is the type of raw material used (whole fish or by-products). By-products, such

as those generated by the filleting industry (sometime referred to as white fish meal) have higher

level of ash and lower level of protein than whole fish meals. High level of ash generally affects

digestibility of dry matter and results in high waste outputs, and can also produce mineral

imbalances (e.g. Zn deficiency).

The type of fish used is not necessarily a determinant factor in the quality of the products.

At equal freshness and if the same processing technique is used, whole capelin, anchovy,

herring, menhaden meals will support similar growth. During processing, the drying treatment is

a key factor. Flame-dried products are less digestible and produce lower performances.


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Table 8. Quality Standards of Fish Meal Required for Salmonid Diets.

Compound Levels

Crude protein (%N x 6.25) > 68%

Lipid < 10%

Ash, total < 13%

Salt (NaCl) < 3%

Moisture < 10%

Ammonia-N < 0.2%

Antioxidant (sprayed liquid form) < 200 PPM

ADC dry matter > 85%

ADC crude protein > 90%

Particle size < 0.25 mm

Steam processed

Animal by-products

Animal protein by-products can very useful complementary protein sources in fish diets.

It is important to use highly digestible products with limited ash content. High ash content

ingredients are generally more polluting and the ash dilute useful nutrient. It is especially

important when buying these products to deal with suppliers who consistently provide high

quality products. Apparent digestibility of animal by-product is relatively high (Table 6) and

they have been used at significant levels in practical diet with success. For blood meal, the type

of drying is of primary importance. Spray-drying produce the best results.

Plant protein by-products :

There are several plant proteins and grain by-products that are used on a regular basis in

fish diet formula. Certain plant protein products have a good nutritional value (high in digestible

protein, good amino acid profile) and are economical at the same time. Other products improve

the physical characteristics of the pellets. The incorporation of certain products must be limited


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for various reasons, such as their content in starch and fibre, the presence of antinutritional or

undesirable factors and their acceptability (palatability).

Many plant products contain antinutritional factors. Most plant protein ingredients are

heat treated during processing, which greatly reduce the level of several antinutritional factors,

such as soybean trypsin inhibitors. Excess heat, however, generally decreases the nutritionalquality of plant protein products by destroying amino acids.

Fish diets formulated with high levels of certain plant protein ingredients appear to be

nutritionally adequate but not very acceptable to certain fish species. For example, diets

containing high levels of soybean meal are poorly accepted by chinook salmon and other

salmonids. Recent experimental evidences suggest that soyasaponins may be a factor affecting

performance of salmonids fed soybean meal.

Corn gluten meal is a plant protein ingredients known to be highly palatable for

salmonids. Studies with rainbow trout and Atlantic salmon show that it complements soybean

meal very well nutritionally. Recent results from our laboratory showed that corn gluten meal orcombination of corn gluten meal and soybean meal can replace most of the fish meal without any

effect on performance of the fish. Nonetheless, the incorporation of corn gluten meal must be

limited in food fish production feeds due to its high concentration in xanthophylls which can

produce undesirable pigmentation of the skin and flesh and may compete with expensive

synthetic pigment added in the feed. However, recent evidences from our laboratory do not

support this hypothesis.

Fats and Oils

Fish oil is the main source of lipid in salmonid diet. Marine fish oils are, in general,

excellent sources of long chain n-3 PUFA (EPA & DHA), fatty acids required by salmonid.

Other types of oils and fats can be used in salmonid diets. Vegetable (canola, soya, safflower,

etc.) oils and animal fats (tallow, lard, poultry fat) can also be used at certain levels in feeds

without effect on growth performance and health of the fish.

Rancidity problems: Marine oils are rich in polyunsaturated fatty acids and are susceptible to

rancidity. In all circumstances rancid oil must be avoided in the preparation of fish feeds.

Rancid fat has deleterious effect on some of the nutrients present in fish feed and health of the

fish. fatty liver disease is usually seen in fish fed rancid fat. Histologically, the main feature isthe extreme infiltration of hepatocytes by lipids. Peroxide (PV), thiobarbituric acid (TBA) and

anisidine (AV) values are in general parameters used to determine the degree of rancidity of lipid

sources. Acceptable quality parameters for fish oil as suggested by Cho et al. (1983) are

presented in Table 9. There is no unequivocal technique to measure rancidity and there is still

doubts about the reliability of PV, AV and TBA value. High PV, AV or TBA suggest problems of

lipid deterioration but are not always indicative of harmful rancidity. The easiest way to determine if


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a feed is rancid may be its smell. Feed with a rancid smell must not be fed. It is preferable to

discard such feeds instead of jeopardising the health of the fish by feeding them.

Table 9. Quality Standards of Oils and Lipid in Final Product Required for Salmonid Diets

Parameters Levels

Oils

Iodine value Report value

Peroxide value < 5 meq/kg

Anisidine value < 10

Pesticides, total < 0.4 PPMPCB's < 0.6 PPM

Nitrogen < 1%

Moisture < 1%

Antioxidant (liquid form)* < 500 PPM

No vitamin fortification

Clean odour

Lipid in final product

Iodine value > 135

n-3 polyunsaturated fatty acids > 15%


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Diet preparation and manufacturing

The are several forms of fish feed, including wet, moist, and steam-pelleted and extruded

dry pellets. However, two basic types of formulated feed are generally used in intensive fish

culture: dry and semi-moist diets. The diets are similar, the basic difference being that semi-moist pellets contain a larger proportion of raw fish and by-products which contribute a higher

moisture level to the final product. Moist feeds have some merit in coastal regions where fresh

raw fish and by-products are regularly available and economical. It is also possible that the

physical characteristics of moist pellets are more palatable to some fish species. However, there

is no evidence that such feeds are nutritionally superior to dry feeds. Moist feed may contain

pathogens since the feed ingredients are only submitted to moderate heat treatment

(pasteurization). In contrast to moist diets, dry feed are heat-treated and generally free from

pathogens. They are also easier to transport and store. The bulk purchase and storage of quality

dry ingredients is possible and ensures a continuous supply of quality feed. The dry ingredients

on the commodity market are more quality defined than raw fisheries products and can be

supplied regularly. Hence it is possible to formulate dry feeds more precisely with the availableknowledge of fish nutrition. Most nutrient in dry feeds are stable are room temperature and

therefore dry feeds can be stored safely without freezing for periods which depend on storage

conditions (approx. 3 months in a cool, shady, and well-ventilated location).

Widely used dry feeds today may divide into three types: (1) steam-pelleted feed; (2)

partially extruded, slow-sinking pellets, and (3) expanded and floating pellets. Feeding dry

pellets either by hand or with automatic feeders is much simpler than that of moist feeds. The

problem of acceptability of dry feeds by some fish species can usually be solved by better

feeding techniques and fish culture management. Otherwise, fry which have difficulty in

accepting dry feeds can be started with semi-moist feed and gradually shifted over to dry feed

within 3-5 weeks.

A formulated dry fish feed must be pelleted and/or crumbled so as to be durable and

water stable. Formulated feeds must also have desirable physical and textural characteristics, and

be of the correct sizes to be readily acceptable by different sizes of fish. Disintegrated and

uneaten feed pollutes the water and creates stresses from low oxygen and high nitrogen and

organic wastes, with serious effects on growth and health. Some of the important factors in

manufacturing a durable, dry fish feed without fines are (1) physical properties of the

ingredients, (2) particle size of ingredients, (3) conditioning time and temperature in the pellet

mill, (4) quality of steam supply, (5) compression pressure through the die, and (6) efficiency of

sifting/grading and fat-spraying equipment. Many of the dietary problems experienced in fish

culture in the past have been related to the physical quality of the pellets and granules, whichwas in turn related to poor quality ingredients, inadequate manufacturing processes, and

negligent practices. Unfortunately for fish feed, the manufacturing process is of crucial

importance. Having to transfer dietary nutrients into the fish through the water medium presents

problems which are unknown in other animal-feeding practices. Therefore, all newly opened

bags should be checked for the presence of excess fines, undersized granules, durability, foreign

particles, too little or too much oil, mildew, and other evidence of poor quality. Any bag or batch

of feed judged to be questionable and any with a detectable rancid smell should not be fed.


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All questionable feed should be immediately reported to a qualified nutritionist and returned to

the manufacturer for replacement.

Table 10. Recommended particle size for salmonid diets

Feed Feed size Feeding

per day

Fish size

(g)

Broodstock Pellets

7 Pt. 6.4 mm x 7 mm long 0.5 - 2 > 200

Grower Pellets

6 Pt. 6.4 mm x 6 mm long 1 - 2 > 200

5 Pt. 4.8 mm x 5 mm long 2 < 2004 Pt. 3.4 mm x 4 mm long 3 100

3 Pt. 2.4 mm x 3 mm long 3 50

Grower Granules

3 Gr. 3 mm 3 < 50

2 Gr. 2 mm 4 20

Starter Granules

1.5 Gr. 1.5 mm 4 < 10

1 Gr. 1 mm 5 3

0.5 Gr. 0.5 mm 6 - 8 1


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8. Feeding Systems

Feeding systems may be defined as all feeding standards and practices employed to deliver

nutritionally balanced and adequate amount of diets to animals, so maintaining normal health and

reproduction together with efficient growth and/or work performance. Until now the feeding of fishhas been based mostly on folkloric practices while the main preoccupation has been to develop

magic diet formulae. Many hypes such as mega-fish meal and mega-vitamin C diets have come

and gone, and we are now in the age of the Norwegian Fish Doughnut (>36% fat diet)! Whichever

diet one decides to feed, the amount fed to achieve optimum or maximum gain is the ultimate

measure of ones productivity in terms of biological gain, economical benefit and/or environmental

sustainability.

Scientific approaches have been used in the feeding of land animals for over a century. The

first feeding standard for farm animals was proposed by Grouven in 1859, and included the total

quantities of protein, carbohydrate and ether extract (fat) found in feeds, as determined by chemical

analysis. In 1864, E. Wolf published the first feeding standard based on the digestible nutrients infeeds.

Empirical feeding charts for salmonids at different water temperatures were published by Deuel and

his colleagues and were likely intended for use with meat-meal mixture diets widely in use at that

time. Since then several methods of estimating daily feed allowance have been reported.

Unfortunately all methods have been based on the body length increase or live weight gain, and dry

weight of feed and feed conversion, rather than on biologically available energy and nutrient

contents in feed in relation with protein and energy retention in the body. These methods are no

longer suitable for todays energy- and nutrient-dense diets, especially in the light of the large

amount of information available on the energy metabolism of salmonids.

Many problems are encountered when feeding fish, much more so than with feeding domestic

animals. First, delivery of feed to fish in a water medium requires particular physical properties of

feed together with special feeding techniques. It is not possible in the literal sense to feed fish on an

"ad libitum" basis, like it is done with most farm animals. The nearest alternative is to feed to "near-

satiety" with very careful observation over a pre-determined number of feedings per day; however,

this can be very difficult and subjective. Feeding fish continues to be an "art" and the fish culturist,

not the fish, determines "satiety" as well as when and how often fish are fed. The amount of feed not

consumed by the fish can not be recovered and, therefore, feed given to them must be assumed eaten

for inventory and feed efficiency calculations. This can cause appreciable errors in feed evaluation

as well as in productivity and waste output calculations. Meal-feeding the fish pre-allocated amounts

by hand or mechanical device based on theoretical energy requirement may be the only logicalchoice. Uneaten feed represents an economical loss and becomes 100% solid and suspended wastes!

Meal-feeding a pre-allocated amount of feed calculated based on the theoretical energy requirement

of the animal may not represent a restricted feeding regime as suggested by some since the amount

of feed calculated is based on the amount of energy required by the animal to express its full growth

potential.


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There are few scientific studies, based on nutrition and husbandry, on feeding standards and

practices; however, there are many duplications and "desktop" modifications of old feeding charts

with little or no experimental basis. Since the mid-1980's, development of high fat diets has led to

most rations being very energy-dense, but feeding charts have changed little to reflect these changes

in diet composition. Most feeding charts available today tend to over-estimate feed requirements

and this overfeeding has led to poor feed efficiencies under most husbandry conditions, and thisrepresent a significant, yet avoidable, waste of resources for aquaculture operations. In addition, it

may results in self-pollution which in turn may affect the sustainability of aquaculture operations.

Recent governmental regulations imposing feed quota, feed efficiency guidelines and/or stringent

waste output limit may somewhat ease the problem. Sophisticated feed management systems, such

as underwater video camera or feed trapping devices, have been developed to determine fish

satiation or the extent of feed wastage and are promoted by many as a solution to overfeeding.

However, regardless of the feeding system or method used, accurate growth and feed requirement

models are needed in order to forecast growth and objectively determine biologically achievable

feed efficiency (based on feed composition, fish growth, composition of the growth). These

estimates can be used as yardsticks to adjust feeding practices or equipment and to compare results

obtained.

The development of scientific feeding systems is one of the most important and urgent

subjects of fish nutrition and husbandry because, without this development, nutrient dense and

expensive feeds are partially wasted. Sufficient data on nutritional energetics are now available to

allow reasonably accurate feeding standards to be computed for different aquaculture conditions.

Presented here is a summarized review of the basis of a nutritional energetic approach to estimating

feed requirement and waste output of fish culture operation as well as the development of the Fish-

PrFEQ computer program. Results obtained from a field station are presented and provide a

framework to examine the type of information that can be derived from bioenergetic models and

generate a feed requirement scenario for the next production year.

PRODUCTION RECORDS

Evaluating and/or predicting growth performance of a fish culture operation or a stock of

fish firstly requires production records of past performance. These records may become databases

for calculating growth coefficients, temperature profiles during growth period and feed intake and

efficiency for various seasons etc. One such production records for a lot of rainbow trout from a

field station is shown in Table 11. A lot of 100 000 fish was reared over a 14-month (410 days)

production cycle between May, 1995 and June, 1996. Cumulated live weight gain (fish production)

was 72 tonnes with feed consumption of 60 tonnes which gave an overall feed efficiency (gain/feed)

of 1.19 (ranged between 1.11 1.22). Water temperature ranged from 0.5C in winter to 21C insummer which is typical of most lakes in Ontario. In spite of the wide fluctuation in water

temperature, the thermal-unit growth coefficients (TGC) was fairly stable ranging between 0.177

0.204. Total mortality was around 9% over 410 days.

From the production record (Table 11) one can extrapolates an overall growth coefficient of

0.191 and this coefficient can be used for the growth prediction of next production cycle with

assumption of similar husbandry conditions and fish stock are used. Total feed requirement and


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weekly or monthly feeding standards can be computed on the basis of this growth predictions plus

the quality of feed purchased.

Table 11.- Fish production records from a field station

Month-

End

Days No.

Fish

Weight

(g/fish)

TGC Total

Biomass

(kg)

Total

Feed

(kg)

Gain/

Feed

Temp

(C)

Flow Rate

(L/min)

1995Initial 100000 10.00

May 15 98900 12.05 0.184 1191.75 167 1.22 5.00 2500

Jun 30 95000 36.45 0.189 3462.75 2000 1.18 18.00 6000

Jul 31 95000 89.84 0.197 8534.80 4300 1.18 19.00 10000

Aug 31 94500 177.43 0.175 16767.14 7200 1.15 21.00 16000

Sep 30 94000 296.26 0.184 27848.44 9500 1.18 19.00 20000

Oct 31 93500 396.06 0.199 37031.61 7800 1.20 11.00 25000Nov 30 93200 451.03 0.197 42036.00 4300 1.19 5.50 25000

Dec 31 93000 455.85 0.176 42394.05 400 1.12 0.50 25000

Jan 31 92000 460.77 0.178 42390.84 400 1.14 0.50 25000

Feb 28 91500 465.23 0.177 42568.55 370 1.11 0.50 25000

Mar 31 91200 470.39 0.184 42899.57 420 1.12 0.50 25000

Apr 30 91000 475.54 0.188 43274.14 420 1.12 0.50 25000

May 31 91000 534.65 0.200 48653.15 4500 1.20 5.00 30000

Jun 30 90800 783.37 0.204 71130.00 18500 1.22 18.00 50000

TOTAL 410

days

0.191 60277

kg feed

1.19 13.5 mill. m3

water used

Procedures for the Estimation of Feed Requirement and Waste Output

Using production records as a starting point, feed requirements and waste output can

scientifically be estimated based on the following three concepts:

1) Prediction of growth and nutrient and energy gains

2) Estimation of excretory and feed waste outputs

3) Quantitation of energy and nutrient needs

1) Prediction Of Growth And Nutrient And Energy Gains:


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Accurate prediction of growth potential of a fish stock under given husbandry condition is an

inevitable prerequisite to the estimation of energy or feed requirement (e.g. weekly ration). The

formula most commonly used for fish growth rate expression is instantaneous growth rate known as

"specific growth rate (SGR)" which is based on the natural logarithm of body weight:

SGR = (ln FBW - ln IBW) / D. (1)

where

FBW is final body weight (g)

IBW is initial body weight (g)

D = number of days

SGR has been widely used by most biologists to describe growth rate of fish. However, the

exponent of natural logarithm underestimates the weight gain between the IBW and the FBW used

in the calculation and it also grossly overestimates predicted body weight at weights greater than

FBW used. Furthermore the SGR is dependent on the IBW, making meaningless comparisons ofgrowth rates among different groups unless IBW are similar.

A more accurate and useful coefficient for fish growth prediction in relation to water

temperature is based on the exponent 1/3 power of body weight. Such a cubic coefficient has been

applied both to mammals and to fish. The following modified formulae were applied to many

nutritional experiments:

Thermal-unit Growth Coefficient (TGC)

= [FBW1/3

- IBW1/3

] /[T x D] x 100 (2)

Predicted Final Body Weight= [IBW

1/3+ (TGC/100 x T x D)]

3 (3)

where:

T is water temperature (C)

(NOTE: 1/3 exponent must contain at least 4 decimals (e.g. 0.3333) to maintain good accuracy)

This model equation has been shown by experiments in our laboratory and several field

stations to represent very faithfully the actual growth curves of rainbow trout, lake trout, brown

trout, chinook salmon and Atlantic salmon over a wide range of temperatures. Extensive test datawere also presented by Iwama and Tautz (1981). An example of the relationship among growth,

water temperature and TGC is shown in Figure 11. Growth of some salmonid stocks used for our

experiments in freshwater gave the following TGC:

Rainbow trout-A 0.174


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Rainbow trout-B 0.153

Rainbow trout-C 0.203

Lake trout 0.139

Brown trout 0.099

Chinook salmon 0.098

Atlantic salmon-A 0.060Atlantic salmon-B 0.100

Since these TGC values and growth rate are dependent on species, stock (genetics), nutrition,

environment, husbandry and others factors, it is essential to calculate the TGC for a given

aquaculture condition using past growth records or records obtained from similar stocks and

husbandry conditions.

Once the expected TGC and water temperature profile during the production period are

established, expected live weight gain (LWG) and recovered energy (RE), nitrogen (RN) and

phosphorus (RP) on basis of dry matter (DM, 20-35% of live body weight) in carcass can becomputed in the following manners:

LWG = FBW - IBW (4)

RE (or RN, RP) = LWG x DM x GE (or N, P) (5)

where

LWG is live weight gain (g)

FBW is final body weight (g)

IBW is initial body weight (g)

RE, RN, RP are the recovered energy (kJ), nitrogen (g) and phosphorus (g)

DM is dry matter content (%) of the fish

GE, N, P is gross energy (kJ), nitrogen (%) and phosphorus (%) content of dry matter

Because of a large proportion of the nutrients (e.g. protein, lipid) and, consequently of the

dietary energy, consumed by fish is retained as carcass body constituents, carcass energy gain is a

major factor driving dietary energy requirement of the fish. Carcass moisture, protein and fat

contents in various life stages dictate energy level of fish. These factors are influenced by species,

genetics, size, age and nutritional status. The dry matter and fat contents of the fish produced are, in

general, the most variable factors and have a determinant effect on energy content of the fish. For

example, relatively fatty Atlantic salmon and rainbow trout may require more dietary energy per unit

of live body weight than leaner salmonids such as brown trout, lake trout and charr. Fish containing

less moisture (more dry matter) and more fat require more energy allocation in feeding standards.

The simplistic assumption of the constant body composition within a growth stanza in

certain published models is not necessarily valid for different species and sizes. Dry matter and

energy content of fish can increase dramatically within a growth stanza, especially in the case of

small fish. Underestimation or overestimation of the feed requirement is likely to occur if constant

carcass energy content is assumed in calculations. Reliable measurements of carcass composition of

fish at various size are essential. Nutrient and energy gains should be calculated at relatively short

size intervals as possible, at least for small fish (


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notably the digestible protein to digestible energy ratio and the lipid content of the diet, can have a

very significant influence on the composition and energy content of the carcass. Estimation of

carcass composition and energy content should rely on data obtained with fish fed diets similar to

those one intends to use.

2) Estimation of Excretory And Feed Waste Outputs:

Waste output loading from aquaculture operations can be estimated using simple principles

of nutrition and bioenergetics. Ingested feedstuffs must be digested prior to utilization by the fish

and the digested protein, lipid and carbohydrate are the potentially available energy and nutrients for

maintenance, growth and reproduction of the animal. The remainder of the feed (undigested) is

excreted in the feces as solid waste (SW), and the by-products of metabolism (ammonia, urea,

phosphate, carbon dioxide, etc.) are excreted as dissolved waste (DW) mostly by the gills and

kidneys.

The total aquaculture wastes (TW) associated with feeding and production is made up ofSW and DW, together with apparent feed waste (AFW):

TW = SW + DW + AFW (6)

SW, DW and AFW outputs are biologically estimated by:

SW = [Feed consumed x (1-ADC)] (7)

DW = (Feed consumed x ADC) - Fish produced (nutrients retained) (8)

AFW = Actual feed input Theoretical feed requirement (9)

in which ADC is the apparent digestibility coefficients of diets. Measurements of ADC and feedintake provide the amount of SW (settled and suspended, AFW-free) and these values are most

critical for accurate quantification of aquaculture waste. ADC for dry matter, nitrogen and

phosphorus should be determined using reliable methods by research laboratories where special

facility, equipment and expertise are available. More information on the equipment and procedures

may be obtained from the website www.uoguelph.ca/fishnutrition.

DW (N or P) can be calculated by difference between digestible N or P intake and retained N

(RN) or P (RP) in the carcass if this information is available, or by using a digested nutrient retention

efficiency (NRE = Retained/Intake). Reliable NRE are necessary and should be determined or

estimated for each type of diet used by research laboratories where expertise is available. However,

controlled feeding and growth trial(s) with particular diets at production sites are essential to validateand fine-tune the coefficients from the laboratory. Dissolved nitrogen output depends very much on

dietary protein and energy ratio and amino acid balances and rate of protein deposition by the fish,

therefore all coefficients must be determined on a regular basis, particularly when feed formulae are

changed. Assuming constancy of many coefficients is a dangerous exercise.

Accurate estimation of total solid waste (TSW) requires a reliable estimate of AFW.

Feeding the fish to appetite or near satiety is very subjective and unfortunately TW contains a


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considerable amount of AFW under most fish farming operations. The use of biomass gain x

feed conversion as an estimate of real feed intake of the fish to calculate waste output used in

certain waste output prediction models can grossly overestimate the feed intake in many operation

where overfeeding is common and result in an underestimation of the TSW output.

It is very difficult scientifically to determine the actual feed intake by fish in spite of manyattempts (mechanical, radiological and biological) that have been made by biologists. Since

estimation of AFW is difficult and almost impossible, the best estimates can be made based on

energy requirements and expected gain in which the energy efficiency (energy gain/intake)

indicates the degree of AFW for a given operation. The theoretical feed requirement (TFR) can be

calculated based on nutritional energetic balance as follows:

TFR = Retained + Excreted (10)

and the amount of feed input above the TFR should be assumed as AFW and all nutrient contents of

the AFW must be included in solid waste quantification. This approach may yield relatively

conservative estimates.

Biological procedures based on the ADC for SW and comparative carcass analyses for DW

were shown to provide very reliable estimates. Biological methods are flexible and capable of

adaptation to a variety of conditions and rearing environments. It also allows estimation of the

theoretical feed requirement and waste output under circumstances where it would be very difficult

or impossible to do so with a chemical/limnological method (e.g. cage culture). Properly conducted

biological and nutritional approaches to estimate aquaculture waste outputs are not only more

accurate but also more economical than chemical/limnological method.

The waste outputs from the field station (see Table 11) are tabulated in Table 12. SW was

estimated at 10 610 kg (fish production 72 t; 60 t feed input over 14 months). SW represented 90%of TSW, since AFW (actual feed input theoretical feed requirement) was estimated at 1 201 kg or

2 % of feed input (60 277 kg in Table 11). The TSW outputs were equivalent to 164 kg per tonne

fish produced. Phosphorus waste was 5.11 kg/t fish produced and nitrogen 30.64 kg. Total water

consumption during 14 months was 13 469 m3, therefore the average effluent quality can be

estimated at: solid 0.877 mg/L, nitrogen 0.163 and phosphorus 0.027 (Table 12). The diet (MNR-

91HG) and the procedures to estimate waste production as well as comparative data of chemical and

biological estimations from field experiments at the Ontario Ministry of Natural Resources (OMNR)

Fish Culture Stations are described elsewhere (Cho et al., 1991, 1994).


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Table 12 - Waste outputs and effluent quality from fish production operation in Table 1

WASTE OUTPUT

(Total Load Estimate)

Solid

(kg)

Nitrogen

(kg)

Phosphorus

(kg)

Feed Wastage (2.2 %) * 1201 80.69 12.008

Solid 10610 356.49 212.194

Dissolved - 1764.60 143.231

TOTAL 11811 2201.79 367.433

- per tonne fish produced 164.3 30.64 5.113

- % of dry matter fed 21.8 % 60.4 % 67.7 %

Average CONCENTRATION (mg/L)

in EFFLUENT (13469 mill. L)

during 410 days

0.877 0.163 0.027

* Actual amount of feed fed Theoretical amount of feed required

3) Quantitation Of Energy And Nutrients Needs

3.1) Dietary energy and protein requirements

A relatively large portion of dietary energy is expended for maintenance or basal

metabolism, which is the minimum energy and nutrients required necessary to maintain basic life

processes. Maintenance energy requirement is approximately equal to the heat production of a

fasting animal. This amount of dietary energy represent as an absolute minimum of "energy-

yielding" nutrients must be covered before any nutrients can be used for growth and reproduction of

the animal. Otherwise body tissues will be catabolized because of a negative energy balance

between intake of dietary fuels and energy expenditure.

A review of available data suggest that a HEf of about 36-40 kJ/kg0.824

per day appear

accurate for rainbow trout at 15C, at least for fish between 20 and 150 g live weight with which

most of studies have been conducted. Water temperature has a major influence on basal metabolism

of fish. The following equation to estimate HEfof salmonids as a function of water temperature

(10):

HEf= (- 0.0104 + 3.26T - 0.05T2) (BW

0.824) D

-1 (11)


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where

HEfis fasting heat production in kJ

T is water temperature (C)

BW is body weight (kg)

D is number of days

Ingestion of food by an animal which has been fasting results in an increase in the

animal's heat production, this heat production is known as heat increment of feeding (HiE). The

physiological basis of this increased heat production includes the post-absorptive processes

related to ingested food, particularly protein-rich food and the metabolic work required for the

formation of excretory nitrogen products, as well as the synthesis of proteins and fats in the

tissues from the newly absorbed, food-derived substrates such as amino acids and fatty acids.

The HiE of rainbow trout fed a balanced diet was observed to be approximately 30 kJ/g

digestible N or the equivalent of 60% HEf(Cho and Kaushik, 1990), but these relationships do

not always hold true. Studies with farm animals suggest that HiE associated with growth may bemore appropriately quantified as a factorial function of protein and lipid deposition rates. Protein

and lipid oxidation rates also appear to contribute to HiE (Cho et al., 1982). Experimental

observations suggest that HiE is approximately equivalent of 17% of net energy intake, i.e.

0.17(RE+HEf) for rainbow trout and other salmonids. This value is used in the bioenergetic

model presented here. Studies are underway to quantify HiE as a function of protein and lipid

deposition and oxidation rates.

Biological oxygen requirement of feeding fish is equal to the total heat production (HEf+

HiE / Qox) in which the oxycalorific coefficient (Qox) used in the model is 13.64 kJ energy per

g oxygen. This represent the absolute minimum quantity of oxygen that must be supplied to the

fish by the aquatic system. Oxygen requirement per unit of BW per hour will vary significantlyfor different fish sizes, water temperatures and growth rates.

3.2) Total energy requirement and calculation of feeding standard

The calculation of total energy requirement and consequently feed allocation of the animal

can be accomplished as follows:

1. Calculation of expected live weight gain (LWG = FBW - IBW) andrecovered energy (RE) based on carcass dry matter content (DM = 20-35% of live

body weight and gross energy (GE) contents = 25-30 kJ/g DM):

RE = LWG x DM x GE (12)


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2. Allocation of approximate maintenance or fasting energy requirement at a

given water temperature (T):

HEf= (- 0.0104 + 3.26T - 0.05T2) (BW

0.824)d

-1 (11)

3. Allocation of approximate heat increment of feeding for maintenance and

growth ration:

HiE = (RE + HEf) x 0.17 (13)

4. Allocation of approximate non-fecal energy loss:

ZE + UE = (RE + HEf+ HiE) x 0.09 (14)

or

5. Theoretical/minimum energy requirement:

TER = 1) + 2) + 3) + 4) = [(RE + HEf) x 1.2753] (15)

6. Feed allowance or feeding standard:

FA = TER / DE x Qfi (16)

Where

TER is theoretical/minimum energy requirement (MJ)

FA is feed allowance (kg)

DE is digestible energy content of the feed (MJ/kg)

Qfi is an adjustment factor

Qfi is an adjustment factor determined by the fish culturist to provide flexibility for

estimating realistic FA under a given husbandry condition (if one observes that more or less feed

may be required than predicted by the model). The minimum digestible energy requirement that

should be fed to the fish is the sum of retained energy (RE) and energy lost as HE f+ HiE + ZE +

UE. The amount of feed can be estimated on a weekly or monthly basis, and recalculated if any

parameter (growth rate, water temperature, etc.) is changed. The computed quantity of feed should

be regarded as a minimum requirement under most conditions and fish culturists should fine-tune the

feeding level to own local conditions using the adjustment factor (Qfi).

The overall energy cost of producing one kg of rainbow trout is around 15-16 MJ DE, but

this ranges from 10 MJ for fry to more than 20 MJ for fish of near 3 kg. Even though maintenanceenergy requirement per kg BW is much higher in small than in large fish, overall energy cost of

production is much higher in large fish because of high "growth-fattening cost". This may become

much more significant when feeding overly high energy (fat) diets, hence more than 50 kJ DE per g

DP (or less than 20 g DP/MJ DE) is not recommended. Water temperature greatly affects heat

production and oxygen consumption of poikilotherms and a growing fish of 100 g is expected to

consumed 110, 210 and 300 mg oxygen/kg BW/hr at 5, 10, 15C, respectively.


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Table 13 summarizes the monthly fish sizes and feed rations predicted by the bioenergetic

models program for the field station based on the production records (see Table 11). The feed

requirements were calculated using a single TGC (0.191) for the whole production cycle (14

months) and actual temperature profile. The nutrient and energy gains used in the calculations were

based on carcass composition values for rainbow trout of various sizes obtained in different

laboratory trials at the University of Guelph. Nutrient and energy retention efficiencies (NRE andERE) used were derived from previous studies at another fish culture station (Harwood Fish Culture

Station, Harwood, Ontario) using comparable diets (Cho et al., 1994). The main discrepancy is

between the actual and predicted feed amount for the first four months with actual feed input being

greater than predicted allocation. This may indicate that overfeeding occurred in 1995, however,

real feed intake by the fish could be somewhere between the predicted amount and the actual

amount. Using this information, the fish culturist can fine-tune the program in the next production

cycle. In the remaining 10 month, the feed allocation estimated by the model was very close to the

actual feed fed, the largest discrepancies (in terms of predicted/actual) occurring at very low water

temperature (0.5C).

This simulation may not be considered a perfect example of independent or objectivevalidation of the model but is, nevertheless, an adequate demonstration of the realism of the

predictions from bioenergetic models. Most of the parameters used in the calculations are fairly

independent from the actual data. For example, the carcass composition data were from a

number of laboratory trials which had nothing to do with actual data. The TGC and the

temperature profile used in the calculation are not independent from the actual data because it is

essential to use actual values or values from previous production cycle if these are available and

repeatable. TGC and water temperature are main inputs required from the fish culturist by the

models. The predicted values from Table 11 were calculated a posterioriand their main use is

as production scenario for following year based on 1995 production performance. The predicted

values can also be used as yardsticks to compare the results obtained with what was predicted to

be biologically achievable and adjust feeding practices or equipment in the following productioncycle.


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Table 13. - Prediction of fish body weight and feed requirement based on 1995 production records in

Table 11.

Month-End

No.Fish

TGC

(%)

BodyWeight

(g/fish)

TotalFeed

(kg)

Gain/Feed

Ratio

BodyWeight

(g/fish)**

TotalFeed

(kg)**

Gain/Feed

Ratio

Temp

(C)

1995

Actual Actual Actual Predicted Predicted Predicted

Initial 100000 10.00 10.00

May 98900 0.184 12.05 167 1.22 12.15 120 1.81 5.0

Jun 95000 0.189 36.45 2000 1.18 37.39 1498 1.68 18.0

Jul 95000 0.197 89.84 4300 1.18 87.94 3446 1.47 19.0

Aug 94500 0.175 177.43 7200 1.15 181.93 6732 1.40 21.0

Sep 94000 0.184 296.26 9500 1.18 310.23 9495 1.35 19.0

Oct 93500 0.199 396.06 7800 1.20 406.58 7775 1.24 11.0

Nov 93200 0.197 451.03 4300 1.19 461.46 4602 1.19 5.5

Dec 93000 0.176 455.85 400 1.12 466.68 451 1.16 0.5

Jan 92000 0.178 460.77 400 1.14 471.94 454 1.16 0.5

Feb 91500 0.177 465.23 370 1.11 477.24 452 1.17 0.5

Mar 91200 0.184 470.39 420 1.12 482.58 453 1.18 0.5

Apr 91000 0.188 475.54 420 1.12 487.96 456 1.18 0.5

May 91000 0.200 534.65 4500 1.20 543.95 4627 1.21 5.0

Jun 90800 0.204 783.37 18500 1.22 780.78 18228 1.30 18.0

** Overall TGC = 0.191 from Table 1 was used to predict body weight and total feed

requirement


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Development ofFish-PrFEQComputer Program

A stand-alone multimedia program for the Windows 95 platform was developed in visual

basic language with database functionality by the Ontario Ministry of Natural Resources. The

program has 4 modules for fish production/growth prediction, waste output quantification, feedallowance estimation and oxygen requirement table and is based on the bioenergetic models

presented above. Feed composition, body weight, water temperature, flow rate and mortality are

entered by the user but waste, retention and other coefficients are parameters that are locked and

may only be revised with an authorized program update diskette. These coefficients should be

determined by qualified nutritionists from feed manufacturers or research institutions since specific

coefficients are required for each type of diets. The use of unrelated coefficients result in under or

overestimation of feed requirements and waste outputs. Live weight gain, feed efficiency, growth

coefficients, solid, nitrogen, phosphorus in the effluent, total waste load, feed ration and oxygen

requirements are some of the output parameters generated by the models.

Factors Affecting Feed Utilization

Feed costs represent a very significant proportion of the production cost in salmonid fish

culture. Many fish culture operations have poor feed efficiencies (gain/feed) and this contributes

to the high cost of production and often results in significant water pollution. It is necessary to

optimize feeding regimes to improve the economical and environmental sustainability of

aquaculture.

It is not always clear if low feed efficiencies observed under certain conditions are due tofeed wastage or due to a real decrease in feed utilization efficiency of the fish. The effect of

feeding level on the efficiency of feed utilization in rainbow trout and other salmonids is the

subject of controversy. It has been suggested that optimum feed efficiency is achieved at feeding

levels below that required for maximum growth in salmonids. Other studies suggest that feed

efficiency improves to its maximum at moderate feed restriction (e.g. 50% of maximum ration)

and this optimum is maintained up to the ration required for maximum growth of the fish. It has

also been suggested that maximum feed efficiency of fish is attained at maximum feed intake

and maximum growth. Most of these observations are derived from studies using fixed ration

(% live body weight) which may not represent the fishs actual feed requirement or studies

conducted under poorly controlled experimental conditions (mechanical distribution of feed,

variable temperature, etc.).

While important from a production point of view, feed efficiency can be a misleading

expression of nutrient and energy utilization. Physical quantity of feed used is not a measure of

biologically available nutrients and energy supplied to the animal. In addition, weight gain does

not always accurately reflect protein, lipid and energy gains since the composition of weight gain

is often variable. Protein deposition is associated with substantial water deposition whereas lipid

depots contain little water. The ratio between protein and lipid deposition will have an impact


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on live weight gain and, consequently, feed efficiency.

Being poikilothermic animals, the metabolic rate, growth, energy expenditure, and feed

intake of fish are highly influenced by water temperature. It is, therefore, important to study

how water temperature affects these parameters, as well as to determine the effect of temperature

on the efficiency of nutrient and energy utilization. Studies have suggested that temperature canaffect the efficiency of energy utilization in salmonids.

The effect of feeding level and water temperature on feed utilization was recently re-

examined under highly controlled conditions (careful hand-feeding to avoid feed waste,

controlled temperature, etc.). The results from the study indicated that fish consuming more feed

as a result of an increase in water temperature or an increase feed allocation grew faster but

appeared to utilise digestible nutrients with similar efficiencies (Table 14, Figure 2). Feeding

level or water temperature had very little effect on feed efficiency. The main factors affecting

feed efficiency of fish fed a balanced practical diet under practical is, therefore, feed wastage.

Feeding frequency and timing is another factor that has been suggested as affecting feedintake and utilization by fish. On a weekly basis, studies have suggested that feeding the

equivalent of six days a week resulted in growth performance similar to feeding 7 days a week.

Feeding five days a week resulted, however, in significantly less growth (Table 15). There is no

good evidence that daily feeding frequency and timing affect feed utilization. The most

important factor is to insure frequent and spaced enough meals to insure that the animal can

consumed enough feed to meet its growth potential. This generally means more frequent feeding

for fish of smaller size. Table 10 provides informal guidelines for daily feeding frequency (# of

meal/day) as a function of fish size. There is, in general, slight between and within day

variations in the appetite of fish, especially if they are free to choose when to feed (i.e. with a

demand feeder). Fish will, however, easily adapt to a feeding schedule. Being attentive to

changes in appetite of fish is, nevertheless, a very important skill fish culturist must acquire.


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Table 14. Growth performance and feed efficiency of rainbow trout (IBW=13.3 g/fish) fed the

experimental diet for 12 weeks at 3 feeding levels and 4 water temperatures. N = 3 for each

feeding level within temperature and for each temperature.

Watertemp.

Feedinglevel

Weightgain

(g/fish)

Feedintake

1

(g/fish)

FE2

(gain : feed)

Thermal - unit GrowthCoefficient (TGC) (%)

6oC NS

R1

R2

SEM

HSD

24.8a z

20.4b

17.5c

0.32

1.60

23.0a z

18.2b

15.3c

0.16

0.82

1.15a z

1.20a

1.22a

0.024

0.12

0.188a z

0.163b

0.143c

0.0016

0.0081

9oC NS

R1

R2

SEMHSD

47.4a y

37.7b

32.5c

0.582.91

39.8a y

30.0b

25.7c

0.241.21

1.27a y

1.34a

1.34a

0.0220.11

0.204a z

0.175b

0.159c

0.00130.0065

12oC NS

R1

R2

SEM

HSD

71.3a x

58.5b

49.9c

1.23

6.21

62.0a x

47.4b

40.1c

0.55

2.75

1.22b y z

1.31ab

1.32a

0.019

0.10

0.192a z

0.172b

0.159c

0.002

0.010

15oC NS

R1

R2

SEM

HSD

96.8a w

74.4b

63.9c

2.06

10.38

86.3a w

63.6b

53.7c

1.52

7.67

1.19a y z

1.25a

1.26a

0.027

0.12

0.191a z

0.164b

0.149c

0.0026

0.0129

NS = near satiation, R1, R2 = restricted diets. SEM = standard error of mean. HSD = Tukeys

honestly significant difference (P< 0.05). Means in the same column (within each temperature)

with different superscripts (a, b, c) are statistically different (P< 0.05). The superscripts w, x, y,

z are used for comparing results between temperatures at the NS feeding level (P < 0.05).1weight as fed basis,

2FE = wet weight gain / dry feed.


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Figure. 2 Efficiency of metabolizable energy utilization above maintenance by rainbow trout at

various water temperatures and feeding levels.

0

50

100

150

200

250

0 50 100 150 200

ME intake - HeE (kJ/kg MBW)

RE(kJ/kgMBW)

6C

9C

12C

15C

Table 15. Effect of weekly feeding frequency on growth and feed efficiency of rainbow trout.

No. of days fed / week

7 6* 5** SEM HSD

Gain, g/fish 84.9a 86.2a 70.0b 2.2 13.1

Feed efficiency, gain:feed 0.70 0.70 0.70

Initial weight = 6.1 g/fish

n= 2 tanks per treatment, Duration = 168 days, water temperature = 15C* No feeding on Sunday

** No feeding on Saturday and Sunday

SEM = pooled standard error of a mean

HSD = Tukeys Honestly Significant Difference

Mean in the same row not sharing the same subscript are significantly different (P


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Reference and Suggested Readings

Azevedo P.A., Cho C.Y., Bureau D.P., Effects of feeding level and water temperature on growth,

nutrient and energy utilization and waste outputs of rainbow trout (Oncorhynchus mykiss). Aquat.

Living Resour. 11 (1998) 227-238 .

Cho, C.Y., Bureau, D.P., Development of bioenergetic models and the Fish-PrFEQsoftware to

estimate production, feeding ration and waste output in aquaculture. Aquat. Living Resour. 11

(1998) 199-210.

Cho C.Y., Bureau D.P., Reduction of waste output from salmonid aquaculture through feeds and

feeding. Progress. Fish. Cult. 59 (1997) 155-160.

Cho C.Y., Cowey C.B., Watanabe T., Finfish nutrition in Asia, Methodological approaches to

research and development. International Development Research Centre, Ottawa. Publication No.

IDRC-233e (1985) 154 p.

Cho C.Y., Feeding systems for rainbow trout and other salmonids with reference to current estimates

of energy and protein requirements. Aquaculture 100 (1992) 107-123.

Cho C.Y., Fish nutrition, feeds, and feeding with special emphasis on salmonid aquaculture. Food

Rev. Int. 6 (1990) 333-357.

Cho C.Y., Hynes J.D., Wood K.R., Yoshida H.K., Development of high nutrient-dense, low

pollution diets and prediction of aquaculture wastes using biological approaches, Aquaculture 124

(1994) 293-305.

Cho C.Y., Hynes J.D., Wood K.R., Yoshida H.K., Quantitation of fish culture wastes by biological

(nutritional) and chemical (limnological) methods; the development of high nutrient dense (HND)

diets, In: Cowey C.B., Cho C.Y. (eds) Nutritional Strategies and Aquaculture Waste, Proceedings

of the 1st International Symposium on Nutritional Strategies in Management of Aquaculture Waste,

University of Guelph, Ontario, Canada (1991) pp.37-50.

Cho C.Y., Kaushik S.J., Nutritional energetics in fish: energy and protein utilization in rainbow trout

(Salmo gairdneri), World Rev. Nutr. Diet. 61 (1990) 132-172.

Cho C.Y., Slinger S.J., Bayley H.S., Bioenergetics of salmonid fishes: Energy intake, expenditure

and productivity, Comp. Biochem. Physiol. 73B (1982) 25-41.

Iwama G.K., Tautz A.F., A simple growth model for salmonids in hatcheries, Can. J. Fish. Aquat.

Sci.,38 (1981) 649-656.

Shearer K.D., Factors affecting the proximate composition of cultured fishes with emphasis on

salmonids, Aquaculture 11 (1994) 63-88.

Bureau and Cho 1999 Introduction to Nutrition and Feeding of Fish

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