Nutritional and physiological strategies for sustainable aquaculture challenges in nutrition
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Nutritional and Physiological Strategies for Sustainable Aquaculture: Challenges in Nutrition. Christopher Kohler and Craig Kasper Fisheries and Illinois Aquaculture Center Southern Illinois University Carbondale. What is fish nutrition? “ Nutrition is the process by which an

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Nutritional and Physiological Strategies for Sustainable Aquaculture: Challenges in Nutrition

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Nutritional and physiological strategies for sustainable aquaculture challenges in nutrition

Nutritional and Physiological Strategies for Sustainable Aquaculture: Challenges in Nutrition

Christopher Kohler and Craig Kasper

Fisheries and Illinois Aquaculture Center

Southern Illinois University Carbondale


Nutritional and physiological strategies for sustainable aquaculture challenges in nutrition

What is fish nutrition?

“Nutrition is the process by which an

organism ingests, assimilates and utilizes

various nutrients and converts them into

body tissues and/or activities.”

–Robinson et al. 2001


Diversity of species

Diversity of Species

  • Over 20,000 spp. (marine, freshwater, diadromous)

  • All trophic levels above autotrophic

  • Zooplankton first food:

    60% crude protein

    15% lipid

  • Broodstock need dietary HUFA’s


Diversity of gi tract

Diversity of GI Tract:

  • Carnivores: large stomach, short intestine

    hybrid striped bass salmonids

  • Omnivores: moderate size stomach & intestine

    channel catfish

  • Herbivores: small stomachs,

    long intestine

    tilapia grass carp

  • Trituration and digestion

    processes also vary


Bioenergetics fish vs warm blooded animals

Bioenergetics: Fish vs. Warm-blooded Animals

  • Fish are more efficient in protein synthesis

    -catfish, 0.84 g wt/g diet

    -chickens, 0.48 g wt/g diet

  • Nitrogenous wastes excreted through gills (~85%)

  • Little energy to maintain body temperature

    fish (3%) vs. mammals (30%)

  • Less energy needed to maintain position


Nutrient requirements

Nutrient Requirements

  • Fish require high protein/low energy diets, yet require substantially less protein than their forage base does

  • Fish seem to require dietary ω-3 fatty acids

  • Fish can absorb some minerals from water

  • Most fish can’t synthesize ascorbic acid


Protein

Protein

  • Protein is the main nutrient

    in fish feeds (28-55%)

  • Size dependent requirements

    Fry > Fingerlings > Stockers

    > Adults/Brood stock


Protein challenges

Protein Challenges

  • Reduction of fish meal is a primary goal/challenge

    • Why the need?

      Competition for usage

      (swine, poultry, etc.)

      Variable nutrient composition

      (AA’s and FA’s)

      Finite resource

      Expensive


Fish meal usage

Fish Meal Usage

30 MMT


Protein challenges1

Protein Challenges

  • Plant feedstuffs generally low protein/high carb.

    soybean meal: good protein & amino acid profile

  • Plant feedstuffs contain “antinutritional” factors

    such as phytic acid, trypsin inhibitors, lectins, etc.

    -may render protein and minerals unavailable

    -decreases weight gain

    -increases phosphorus into effluents


Protein challenges2

Protein Challenges

  • Plant usage increases fecal output

  • Plant based diets = amino acid deficiencies

    eg. lysine & methionine

  • Supplementation increases diet cost


Carbohydrates

Carbohydrates

  • Some fish can tolerate high carbohydrate feeds

    tilapia carp catfish pacu

  • Spares protein for muscle synthesis

  • Inexpensive energy source

  • Many sources:

    wheat corn

    yucca plantain


Carbohydrate challenges

Carbohydrate Challenges

  • Not required, excess will decrease protein gain

    (Carnivorous fish have been on the Atkins diet for eons.)

  • Fish have poor control over blood glucose

    • post prandial levels rise rapidly, yet take hours to decline, may effect liver health

    • reduced growth in largemouth bass fed diets containing 13% carbohydrate


Lipids

Lipids

  • Fish require 4-16% dietary fat

    -Requirement is also size dependent

  • Main energy source of feeds

  • Spares protein for growth

  • Certain fatty acids required:

    18:2n-6 (Linoleic),

    18:3n-3 (Linolenic) = freshwater fish

    20:4n-6 (Arac. acid) = healthy immune response

    20:5n-3 (EPA); 22:6n-3 (DHA) = saltwater fish


Lipid challenges

Lipid Challenges

  • Too much, or wrong ratio, decreases growth, degrades liver & decreases cold tolerance

  • When reducing animal products in feeds, fatty

    acid requirement is more difficult to achieve

  • Moreover, plant-based ω-3 fatty acids are limited to 18-carbon chains

  • Fish oil remains the best

    source of EPA and DHA


Fate of nitrogen and phosphorus from feed

Fate of Nitrogen and Phosphorus from Feed

Retained

30% N

32% P

Food

100% N

100% P

Dissolved

87% N

10-40% P

Effluent

70% N

68% P

Solids

13% N

60-90% P


New topics

New Topics

  • Always emergent species to study:Cobia, Pacu, etc.

  • Finishing diets

  • Alternative protein sources

    • canola protein concentrates

    • barley fractions

    • fermentation bi-products

    • microbial protein production

      (single-celled protein, SCP)


New topics1

New Topics

  • Many nutrient requirements still unknown for many species, particularly minerals

  • Nutriceuticals-using fish as a delivery system for beneficial nutrients

    • EPA/DHA Antioxidants


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