NUTRITION, FEEDS AND FEEDING

• Digestive process in fishes

• Organs involved & function

• Nutritional requirements

• Feed processing/characteristics

• Energy budgets

• Feeding regimes/rates

AILIMENTARY TRACK

• Oral Cavity - Mouth, Teeth

• Esophagus

• Stomach - Cardiac and Pyloric

• Intestine – Small, large and rectum

Digestive Organs - Liver

• LIVER - Process and storage of lipids and carbohydrates, production of plasma proteins

•

• Formation of bile

Gall Bladder

• Stores bile and secretes into gut –

• Bilirubin (yellow color) – oxidizes to biliverdin (blue-green) over time•

Digestive Organs- Pancreas

Exocrine• Scattered islands of secretory tissue in

mesentery pyloric caeca

Endocrine - Islets of Langerhans

• Insulin and glucagon production for carbohydrate, fat and protein metabolism

Classifications of fish species

Coldwater: Carnivores

Coolwater: Carnivores or omnivores

Warmwater: Herbivores or omnivores

• Feed must meet specific dietary requirements

NUTRITION, METABOLISM AND GROWTH

•

•

•

Proximate analysis

Feed formulated based on analysis of individual ingredients

• Moisture• Ether extract – fat soluble vitamins, carotene,

chlorophyll, sterols, waxes, fats and fatty acids• Ash• Crude fiber – low digestible plant carbohydrates• Nitrogen-free extract (NFE) – consists mainly of

digestible carbohydrates

PROTEIN

• 30-50% in most fish diets• IMPORTANT FOR FISH – structure/muscle,

gonads and growth • Proteins – • • Linear relationship between daily protein and

growth • Utilization of protein relatively constant and

independent of feeding - (carnivore, omnivore, herbivore)

CARBOHYDRATES

• Not very important for most fish species

• Appear as sugars and starches

• Trout have limited ability to digest sugars/starches–

• May affect fish health

– Catfish digest starch well –

CARBOHYDRATES

• Fish lack the enzyme cellulase– Unable to break down cellulose– Fiber usually considered to have 0 nutritional

value

• Cellulose often used as binding agent• Levels of 10 to 20% have resulted in

growth depression in rainbow trout–

• Catfish?

LIPIDS

• Lipids for energy, structure and function of _____________

• Fish utilize lipids with low melting points (Pu fa) - polyunsaturated fatty acids– Typically supplied in diets from 7-16%

ESSENTIAL FATTY ACIDS

• Triglycerides with polyunsaturated fatty acids

• w 3 and w 6 - Omega or linolenic series (n- series) of fatty acids

• Digestibility of lipids is 85-95%• Major source is fish oil (salmonids) or

soybean oil (ictalurids)

MINERALS• Required by all animals – fish can uptake some

from water– Formation of skeletal tissue– Respiration– Digestion– Osmoregulation (SW = high minerals/salts, FW = low

• Major minerals– Ca, Phos, Sulphur, sodium, chloride ion, K+, Magnesium

• Trace minerals– Cobalt, Copper, Fluorine, Iodine, Iron, Manganese, etc.

MINERALS

• Dietary Phosphorus– –

• Phosphorus reduction– – Increase plant protein

• High in phytate phosphorus

–

VITAMINS

• COMPLEX SUBSTANCES

• FAT SOLUBLE VITAMINS– A- Retinol - carotenoids converted in

intestinal mucosa– E - Tocopherol - antioxidants in fish diets*– K - Two forms in green plants - blood

clotting and bacteriostatic– D - calciferols not well understood

WATER SOLUBLE VITAMINS

• B1 - coenzyme of carbohydrate metab

– digestion, reproduction, nervous system

• B2 - Riboflavin- eyes function, cataracts

• B6 - Pyridoxin

• Pantothenic acid– Lamellar hyperplasia

• Inositol - reduced growth rates

WATER SOLUBLE VITAMINS

• Niacin - haemorrhage erosion epidermis

• Biotin - can cause darkening anorexia

• Choline -poor growth and conversion

• Cyanocobalamic (B12)- anemia

• Folic acid - haemopoiesis - erythrocytic anemia

WATER SOLUBLE VITAMINS

• Ascorbic Acid (C) *– Important - Collagen skeletal systems– Wound healing, disease resistance– Fish and primates can not synthesize

Other dietary factors• Attractants

– Attract fish by sight or smell (shrimp meal, fish oil, fish meal, etc.)

–

• Pigments– External

• Crayfish, red snapper, koi, etc.

– Flesh color – pink in salmon or trout• • Must be obtained from feed (crustaceans, yeast, plants/algae)

Other dietary factors

• Behavior– How a feed particle moves through water

column •

•

•

• Mimic natural food

Practical diets

• Dry feeds:–

– Made from all dry ingredients with addition of liquid fat (fish or oilseed oil)

– Pellets, crumbles, or flakes– Floating or sinking feeds of various size

designations

Practical diets

• Pellets:– Feed ingredients mixed and forced under

pressure through different size dies

– Stability varies depending on binders used

–

Practical diets

• Microencapsulated – small particles of uniform nutritional make up:– Slurry of fine ground ingredients– Encased in proteinaceous membrane (microcapsule)– Expensive, but used for some species (larval marine)

• Moist and Semi-moist feeds (OMP – 32% moisture)– Formulated with high % of whole fish–

– Stored frozen

Practical diets

• Extruded feeds/pellets:– Mixed ingredients passed through extruder

barrel–

– Floating, slow sinking, and stable pellet– Increase lipid content (energy) by spraying

extruded feeds after process– Enhanced digestibility of some ingredients–