Nutritional and Physiological Nutritional and Physiological Strategies for Sustainable Strategies for Sustainable

Aquaculture: Aquaculture:

Challenges in NutritionChallenges in Nutrition

Christopher Kohler and Craig KasperChristopher Kohler and Craig Kasper

Fisheries and Illinois Aquaculture CenterFisheries and Illinois Aquaculture Center

Southern Illinois University CarbondaleSouthern Illinois University Carbondale

What is fish nutrition?What is fish nutrition?

““Nutrition is the process by which an Nutrition is the process by which an organism ingests, assimilates and utilizesorganism ingests, assimilates and utilizes various nutrients and converts them intovarious nutrients and converts them into body tissues and/or activities.”body tissues and/or activities.”

– –Robinson et al. 2001Robinson et al. 2001

Diversity of SpeciesDiversity of Species

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

• All trophic levels above autotrophicAll trophic levels above autotrophic

• Zooplankton first food: Zooplankton first food:

60% crude protein60% crude protein

15% lipid15% lipid

• Broodstock need dietary HUFA’sBroodstock need dietary HUFA’s

Diversity of GI Tract:Diversity of GI Tract:

• Carnivores: large stomach, short intestineCarnivores: large stomach, short intestine hybrid striped bass salmonidshybrid striped bass salmonids

• Omnivores: moderate size stomach & intestineOmnivores: moderate size stomach & intestine channel catfishchannel catfish

• Herbivores: small stomachs,Herbivores: small stomachs, long intestinelong intestine tilapia grass carp tilapia grass carp

• Trituration and digestion Trituration and digestion processes also varyprocesses also vary

• Fish are more efficient in protein synthesisFish are more efficient in protein synthesis -catfish, 0.84 g wt/g diet-catfish, 0.84 g wt/g diet-chickens, 0.48 g wt/g diet-chickens, 0.48 g wt/g diet

• Nitrogenous wastes excreted through gills (~85%)Nitrogenous wastes excreted through gills (~85%)

• Little energy to maintain body temperature Little energy to maintain body temperature fish (3%) vs. mammals (30%)fish (3%) vs. mammals (30%)

• Less energy needed to maintain positionLess energy needed to maintain position

Bioenergetics: Fish vs. Warm-blooded AnimalsBioenergetics: Fish vs. Warm-blooded Animals

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

• Fish seem to require dietary Fish seem to require dietary ωω-3 fatty acids-3 fatty acids

• Fish can absorb some minerals from waterFish can absorb some minerals from water

• Most fish can’t synthesize ascorbic acidMost fish can’t synthesize ascorbic acid

Nutrient RequirementsNutrient Requirements

ProteinProtein

• Protein is the main nutrient Protein is the main nutrient

in fish feeds (28-55%)in fish feeds (28-55%)

• Size dependent requirementsSize dependent requirements

Fry > Fingerlings > StockersFry > Fingerlings > Stockers

> Adults/Brood stock> Adults/Brood stock

Protein ChallengesProtein Challenges

• Reduction of fish meal is a primary goal/challengeReduction of fish meal is a primary goal/challenge– Why the need?Why the need?

Competition for usageCompetition for usage

(swine, poultry, etc.)(swine, poultry, etc.)

Variable nutrient compositionVariable nutrient composition

(AA’s and FA’s)(AA’s and FA’s)

Finite resourceFinite resource

ExpensiveExpensive

Fish Meal Usage Fish Meal Usage

17

55

20

23

48

17

35

24

29

0%10%20%30%40%50%60%70%80%90%100%

1988 1998 2000

OthersSwinePoultryAqua

30 MMT30 MMT

Protein ChallengesProtein Challenges

• Plant feedstuffs generally low protein/high carb.Plant feedstuffs generally low protein/high carb.

soybean meal: good protein & amino acid profilesoybean meal: good protein & amino acid profile

• Plant feedstuffs contain “antinutritional” factors Plant feedstuffs contain “antinutritional” factors

such as phytic acid, trypsin inhibitors, lectins, etc. such as phytic acid, trypsin inhibitors, lectins, etc. --may render protein and minerals unavailablemay render protein and minerals unavailable

-decreases weight gain-decreases weight gain

-increases phosphorus into effluents-increases phosphorus into effluents

Protein ChallengesProtein Challenges

• Plant usage increases fecal outputPlant usage increases fecal output

• Plant based diets = amino acid deficiencies Plant based diets = amino acid deficiencies

eg. lysine & methionine eg. lysine & methionine

• Supplementation increases diet costSupplementation increases diet cost

CarbohydratesCarbohydrates

• Some fish can tolerate high carbohydrate feedsSome fish can tolerate high carbohydrate feeds

tilapia carp catfish pacutilapia carp catfish pacu

• Spares protein for muscle synthesisSpares protein for muscle synthesis

• Inexpensive energy sourceInexpensive energy source

• Many sources:Many sources:

wheat corn wheat corn

yucca plantainyucca plantain

Carbohydrate ChallengesCarbohydrate Challenges

• Not required, excess will decrease protein gain Not required, excess will decrease protein gain (Carnivorous fish have been on the Atkins diet for eons.)(Carnivorous fish have been on the Atkins diet for eons.)

• Fish have poor control over blood glucoseFish have poor control over blood glucose– post prandial levels rise rapidly, yet take hours to post prandial levels rise rapidly, yet take hours to

decline, may effect liver healthdecline, may effect liver health– reduced growth in largemouth bass fed diets containing reduced growth in largemouth bass fed diets containing

13% carbohydrate13% carbohydrate

LipidsLipids

• Fish require 4-16% dietary fat Fish require 4-16% dietary fat -Requirement is also size dependent-Requirement is also size dependent

• Main energy source of feeds Main energy source of feeds

• Spares protein for growthSpares protein for growth

• Certain fatty acids required:Certain fatty acids required: 18:2n-6 (Linoleic),18:2n-6 (Linoleic),

18:3n-3 (Linolenic) = freshwater fish18:3n-3 (Linolenic) = freshwater fish

20:4n-6 (Arac. acid) = healthy immune response20:4n-6 (Arac. acid) = healthy immune response

20:5n-3 (EPA); 22:6n-3 (DHA) = saltwater fish20:5n-3 (EPA); 22:6n-3 (DHA) = saltwater fish

Lipid ChallengesLipid Challenges

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

• When reducing animal products in feeds, fattyWhen reducing animal products in feeds, fatty

acid requirement is more difficult to achieveacid requirement is more difficult to achieve

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

• Fish oil remains the best Fish oil remains the best

source of EPA and DHAsource of EPA and DHA

Fate of Nitrogen and Phosphorus from FeedFate of Nitrogen and Phosphorus from Feed

FoodFood100% N100% N100% P100% P

RetainedRetained30% N30% N32% P32% P

DissolvedDissolved87% N87% N

10-40% P10-40% P

SolidsSolids13% N13% N

60-90% P60-90% P

EffluentEffluent70% N70% N68% P68% P

New TopicsNew Topics

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

• Finishing dietsFinishing diets

• Alternative protein sourcesAlternative protein sources– canola protein concentratescanola protein concentrates– barley fractions barley fractions – fermentation bi-products fermentation bi-products – microbial protein productionmicrobial protein production

(single-celled protein, SCP)(single-celled protein, SCP)

New TopicsNew Topics

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

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

EPA/DHA AntioxidantsEPA/DHA Antioxidants