BioenergeticBioenergetics:s:

Calculating Energy Values Calculating Energy Values in Foodin Food

IntroductionIntroduction Energy is required by all animals to Energy is required by all animals to

sustain lifesustain life SourcesSources: food, natural productivity, : food, natural productivity,

body stores (times of environmental body stores (times of environmental stress or feed deprivation)stress or feed deprivation)

Lecture objectivesLecture objectives: How much energy is : How much energy is needed by aquatic organisms?, How needed by aquatic organisms?, How does it varies from terrestrials?, What does it varies from terrestrials?, What are the sources, how is energy are the sources, how is energy partitioned for various usespartitioned for various uses

Lecture objectivesLecture objectives How much energy is needed by aquatic How much energy is needed by aquatic

organisms?organisms?

How it varies from terrestrials?How it varies from terrestrials?

What are the sources?What are the sources?

How is energy partitioned for various How is energy partitioned for various uses?uses?

IntroductionIntroduction Lavoisier first demonstrated that Lavoisier first demonstrated that oxidationoxidation of of

nutrients was some form of combustion (burning)nutrients was some form of combustion (burning) Rubner (1894) first demonstrated that Rubner (1894) first demonstrated that

fundamental Laws of fundamental Laws of ThermodynamicsThermodynamics also also applied to intact living animal systemsapplied to intact living animal systems

Organic matter Organic matter processes processes CO CO22 + H + H22O + O + energy (released)energy (released)

Understanding energy transforms is only possible Understanding energy transforms is only possible when it is converted from one form to anotherwhen it is converted from one form to another

IntroductionIntroduction EnergeticsEnergetics is the study of energy is the study of energy

requirements and the flow of energy requirements and the flow of energy within systemswithin systems

bioenergeticsbioenergetics is the study of the is the study of the balance between energy intake in the balance between energy intake in the form of food and energy utilization by form of food and energy utilization by animals for life-sustaining processesanimals for life-sustaining processes

processes?processes?: tissue synthesis, : tissue synthesis, osmoregulation, digestion, respiration, osmoregulation, digestion, respiration, reproduction, locomotion, etc.reproduction, locomotion, etc.

IntroductionIntroduction the original energy source for food energy is the original energy source for food energy is

the sun the sun (See…I knew what I was talking about for once!)(See…I knew what I was talking about for once!)

energy from the sun is converted by energy from the sun is converted by photosynthesis into the production of glucosephotosynthesis into the production of glucose

glucose is the hydrocarbon source from which glucose is the hydrocarbon source from which plants synthesize other organic compounds plants synthesize other organic compounds such as COH, protein, lipidssuch as COH, protein, lipids

as previously mentioned, one must consider as previously mentioned, one must consider the quality of these sourcesthe quality of these sources

IntroductionIntroduction Animals are not heat enginesAnimals are not heat engines

They can’t use the multitude of sources of energy They can’t use the multitude of sources of energy we have (e.g., flywheels, falling objects, the tide, we have (e.g., flywheels, falling objects, the tide, etc.)etc.)

Must obtain their energy from chemical bonds of Must obtain their energy from chemical bonds of complex moleculescomplex molecules

How do they do it? In a nutshell, they oxidize How do they do it? In a nutshell, they oxidize these bonds to lower energy states using oxygen these bonds to lower energy states using oxygen from the airfrom the air

TrickTrick: some bonds have more energy than others: some bonds have more energy than others

IntroductionIntroduction most aquaculture animals obtain their most aquaculture animals obtain their

energy from feedsenergy from feeds As mentioned, some bonds have more As mentioned, some bonds have more

energy associated with them than othersenergy associated with them than others when you have many nutrients comprising when you have many nutrients comprising

a feed, the energy level of that feed can a feed, the energy level of that feed can vary vary substantiallysubstantially

availability of energy varies according to availability of energy varies according to feed ingredient and speciesfeed ingredient and species

growth is the endpoint of net energygrowth is the endpoint of net energy

Glycogen Glycogen MoleculeMolecule

major COH storage form of energy

Lipid MoleculeLipid Molecule

another major storage form

Introduction (cont.)Introduction (cont.)

Energy goes through many cycles and Energy goes through many cycles and transformations, always with transformations, always with loss of heatloss of heat

can be released at various rates: gasoline can be released at various rates: gasoline can exploding vs. compost pilecan exploding vs. compost pile

nutritional energeticsnutritional energetics involves the study of involves the study of the sources and transformations of energy the sources and transformations of energy into new products (mainly we are concerned into new products (mainly we are concerned with growth or tissue deposition)with growth or tissue deposition)

of all dry matter we consume, 70-90% goes of all dry matter we consume, 70-90% goes to synthesis of new productsto synthesis of new products

Energy FormsEnergy Forms Matter and energy are basically the sameMatter and energy are basically the same it is often convenient to consider energy a it is often convenient to consider energy a

property of matter (kcal/g feed)property of matter (kcal/g feed) nutritive value of food items is often nutritive value of food items is often

reflected by caloriesreflected by calories what you are used to seeing in the store is what you are used to seeing in the store is

not calories, but kilocalories (kcal’s), or not calories, but kilocalories (kcal’s), or CCaloriealorie

common form of energy in the cell is ATPcommon form of energy in the cell is ATP

Energy FormsEnergy Forms All processes in the animal body involve All processes in the animal body involve

changes in energychanges in energy the word “the word “energyenergy” was first introduced ” was first introduced

in 1807, and defined as “ability to work”in 1807, and defined as “ability to work” found in many forms: heat, kinetic, found in many forms: heat, kinetic,

electromagnetic, radiant, nuclear and electromagnetic, radiant, nuclear and chemicalchemical

for our purposes, chemical energy is the for our purposes, chemical energy is the most important (e.g., ATP)most important (e.g., ATP)

Heat EnergyHeat Energy The measurement of energy requires The measurement of energy requires

converting it from one form to anotherconverting it from one form to another what we typically measure is heat (why?)what we typically measure is heat (why?) according to the according to the first law of first law of

thermodynamicsthermodynamics, all forms of energy can , all forms of energy can be converted quantitatively into heat be converted quantitatively into heat energyenergy

heat energy is represented by the heat energy is represented by the various constituents of the dietvarious constituents of the diet

Heat EnergyHeat Energy however, the body is not a heat however, the body is not a heat

engine, heat is an end product of engine, heat is an end product of reactionsreactions

it is only useful to animals to keep it is only useful to animals to keep the body warmthe body warm

chemical reactions either generate chemical reactions either generate heat (+heat (+H) or require heat (- H) or require heat (- H)H)

Units of Heat Units of Heat EnergyEnergy

The basic unit of energy is the The basic unit of energy is the caloriecalorie (cal) (cal) it is the amount of heat required to raise the it is the amount of heat required to raise the

temperature of 1g of water 1 degree Celsius temperature of 1g of water 1 degree Celsius (measured from 14.5 to 15.5(measured from 14.5 to 15.5ooC)C)

it is such a small unit, that most nutritionists it is such a small unit, that most nutritionists prefer to use the prefer to use the kcalkcal (or 1,000 calories) (or 1,000 calories)

REM:the kcal is more common (supermarket REM:the kcal is more common (supermarket CaloriesCalories))

Other Units of Heat Other Units of Heat EnergyEnergy

BTUBTU (British Thermal Unit) = amount (British Thermal Unit) = amount of heat required to raise 1 lb of water of heat required to raise 1 lb of water 11ooFF

international unit: the international unit: the joulejoule - 1.0 joule - 1.0 joule = 0.239 calories or 1 calorie = 4.184 = 0.239 calories or 1 calorie = 4.184 joulejoule

a a joulejoule (J) is the energy required to (J) is the energy required to accelerate a mass of 1kg at a speed of accelerate a mass of 1kg at a speed of 1m/sec a distance of 1m1m/sec a distance of 1m

Energy Terms (from De Energy Terms (from De Silva and Anderson)Silva and Anderson)

Energy flow is often shown as a diagram: Energy flow is often shown as a diagram: every text has its own idea of a suitable every text has its own idea of a suitable diagram:diagram:

Energy TermsEnergy Terms Gross energy (GE):Gross energy (GE): energy released as energy released as

heat resulting from combustion (kcal/g)heat resulting from combustion (kcal/g) Intake Energy (IE):Intake Energy (IE): gross energy gross energy

consumed in food (COH, lipid, protein)consumed in food (COH, lipid, protein) Fecal Energy (FE):Fecal Energy (FE): gross energy of gross energy of

feces (undigested feed, metabolic feces (undigested feed, metabolic products, gut epithelial cells, digestive products, gut epithelial cells, digestive enzymes, excretory products)enzymes, excretory products)

Digestible Energy (DE):Digestible Energy (DE): IE-FE IE-FE

Energy Terms Energy Terms (cont.)(cont.)

Metabolizable energy (ME)Metabolizable energy (ME): energy in the food minus : energy in the food minus that lost in feces, urine and through gill excretion:that lost in feces, urine and through gill excretion:

ME = IE - (FE + UE + ZE)ME = IE - (FE + UE + ZE) urinary energy (UE)urinary energy (UE): total gross energy of urinary : total gross energy of urinary

products of unused ingested compounds and metabolic products of unused ingested compounds and metabolic products products

gill excretion energy (ZE)gill excretion energy (ZE): : gross energy of products gross energy of products excreted through gills (lungs in mammalian terrestrials), excreted through gills (lungs in mammalian terrestrials), high in fishhigh in fish

surface energy (SE)surface energy (SE): energy lost to sloughing of mucus, : energy lost to sloughing of mucus, scales, exoskeletonscales, exoskeleton

Energy Terms Energy Terms (cont.)(cont.)

Total heat production (HE)Total heat production (HE): energy lost : energy lost in the form of heatin the form of heat

heat lost is sourced from metabolism, thus, heat lost is sourced from metabolism, thus, HE is an estimate of metabolic rateHE is an estimate of metabolic rate

measured by temperature change measured by temperature change (calorimetry) or oxygen consumption rate(calorimetry) or oxygen consumption rate

divided into a number of constituentsdivided into a number of constituents as per energy flow diagram as per energy flow diagram

Energy Flow Energy Flow DiagramDiagram

Energy TermsEnergy Terms (total heat (total heat production)production)

Basic metabolic rate (HBasic metabolic rate (HeeE):E): heat energy released from heat energy released from cellular activity, respiration, blood circulation, etc.cellular activity, respiration, blood circulation, etc.

heat of activity (Hheat of activity (HjjE):E): heat produced by muscular activity heat produced by muscular activity (locomotion, maintaining position in water)(locomotion, maintaining position in water)

heat of thermal regulation (Hheat of thermal regulation (HccE):E): heat produced to heat produced to maintain body temp (above zone of thermal neutrality)maintain body temp (above zone of thermal neutrality)

heat of waste formation (Hheat of waste formation (HwwE):E): heat associated with heat associated with production of waste productsproduction of waste products

specific dynamic action (Hspecific dynamic action (HiiE):E): increase in heat production increase in heat production following consumption of feed (result of metab), varies with following consumption of feed (result of metab), varies with energy content of food, especially proteinenergy content of food, especially protein

Energy UtilizationEnergy Utilization Energy intake is Energy intake is

divided among all divided among all energy-requiring energy-requiring processesprocesses

Magnitude of each Magnitude of each depends on quantity depends on quantity of intake plus animal’s of intake plus animal’s ability to digest and ability to digest and utilize that energyutilize that energy

Can vary by feeding Can vary by feeding mode: carnivorous mode: carnivorous vs. herbivorousvs. herbivorous

From Halver (page 7)

Focus: Gross Focus: Gross EnergyEnergy

Energy content of a substance (i.e., Energy content of a substance (i.e., food) is typically determined by food) is typically determined by completely oxidizing (burning) the completely oxidizing (burning) the compound to carbon dioxide, water and compound to carbon dioxide, water and other gasesother gases

the amount of energy given off is the amount of energy given off is measured and known as measured and known as gross energygross energy

gross energy (GE) is measured by a gross energy (GE) is measured by a device known as a device known as a bomb calorimeterbomb calorimeter

Gross Energy of Gross Energy of FeedstuffsFeedstuffs

Gross Energy of FeedstuffsGross Energy of Feedstuffs

Fats (triglycerides) have about twice the GE Fats (triglycerides) have about twice the GE as carbohydratesas carbohydrates

this is because of the relative amounts of this is because of the relative amounts of oxygen, hydrogen and carbon in the oxygen, hydrogen and carbon in the compoundscompounds

energy is derived from the energy is derived from the heat of heat of combustioncombustion of these elements: C= 8 of these elements: C= 8 kcal/g, H= 34.5, etc.kcal/g, H= 34.5, etc.

typical heat from combustion of fat is 9.45 typical heat from combustion of fat is 9.45 kcal/g, protein is 5.45, COH is 3.75kcal/g, protein is 5.45, COH is 3.75

Available Available EnergyEnergy

Gross energy only represents the energy Gross energy only represents the energy present in present in dry matter (DM)dry matter (DM)

it is not a measurement of its energy value to it is not a measurement of its energy value to the consuming animal!!the consuming animal!!

the difference between gross energy and the difference between gross energy and energy available to the animal energy available to the animal varies greatly varies greatly for different foodstuffsfor different foodstuffs

the key factor to know is how digestible the the key factor to know is how digestible the food item isfood item is

digestible energy also varies by speciesdigestible energy also varies by species

Digestible Digestible EnergyEnergy

The amount of energy available to an animal The amount of energy available to an animal from a feedstuff is known as its from a feedstuff is known as its digestible digestible energy (DE)energy (DE)

REM: DE is defined as the difference REM: DE is defined as the difference between the gross energy of the feed item between the gross energy of the feed item consumed (IE) and the energy lost in the consumed (IE) and the energy lost in the feces (FE)feces (FE)

two methods of determination: two methods of determination: directdirect or or indirectindirect

by the direct method, all feed items by the direct method, all feed items consumed and feces excreted are measuredconsumed and feces excreted are measured

Digestible EnergyDigestible Energy The The indirect method indirect method involves only involves only

collecting a sample of the feed and fecescollecting a sample of the feed and feces digestion coefficients are calculated on digestion coefficients are calculated on

the basis of ratios of energy to indicator the basis of ratios of energy to indicator in the feed and fecesin the feed and feces

indicatorindicator?: an ?: an inertinert indigestible indigestible compound added to the feedcompound added to the feed

indicators: natural (fiber, ash) or indicators: natural (fiber, ash) or synthetic (chromic oxide)synthetic (chromic oxide)

DE CalculationsDE CalculationsDirect MethodDirect Method

% DE =% DE =Feed energy - Fecal energyFeed energy - Fecal energy

Feed energyFeed energyX 100X 100

Indirect Indirect MethodMethod

% DE = 100 - % DE = 100 - Feed energyFeed energy

Fecal energyFecal energyXX

Fecal Fecal indicatorindicator

Feed indicatorFeed indicatorx100x100

Metabolizable Metabolizable EnergyEnergy

Even more detailed! Even more detailed! Represents DE minus energy lost from the Represents DE minus energy lost from the

body through gill and urinary wastesbody through gill and urinary wastes More difficult to determine! Why?More difficult to determine! Why? REM: all urinary wastes in water!!! How do REM: all urinary wastes in water!!! How do

you collect that????you collect that????

%ME = -------------------------------------- x 100Intake energy - (E lost in feces, urine, Intake energy - (E lost in feces, urine, gills)gills)

Feed energyFeed energy

Metabolizable Metabolizable EnergyEnergy

Use of ME vs DE would allow for a much more Use of ME vs DE would allow for a much more absolute evaluation of the dietary energy absolute evaluation of the dietary energy metabolized by tissuesmetabolized by tissues

however, ME offers little advantage over DE however, ME offers little advantage over DE because most energy is used for digestion in fishbecause most energy is used for digestion in fish

energy losses in fish through urine and gills does energy losses in fish through urine and gills does not vary much by feedstuffnot vary much by feedstuff

fecal energy loss is more importantfecal energy loss is more important forcing a fish to eat involuntarily is not a good forcing a fish to eat involuntarily is not a good

representation of actual energy processesrepresentation of actual energy processes

Energy Ratios for Energy Ratios for Rainbow TroutRainbow Trout

Energy Balance in Energy Balance in FishFish

Energy flow in fish is similar to that in mammals and birdsEnergy flow in fish is similar to that in mammals and birds fish are more efficient in energy usefish are more efficient in energy use energy losses in urine and gill excretions are lower in fish energy losses in urine and gill excretions are lower in fish

because 85% of nitrogenous waste is excreted as because 85% of nitrogenous waste is excreted as ammonia (vs. urea in mammals and uric acid in birds)ammonia (vs. urea in mammals and uric acid in birds)

heat increment (increase) as a result of ingesting feed is heat increment (increase) as a result of ingesting feed is 3-5% ME in fish vs. 30% in mammals3-5% ME in fish vs. 30% in mammals

maintenance energy requirements are lower because maintenance energy requirements are lower because they don’t regulate body tempthey don’t regulate body temp

they use less energy to maintain positionthey use less energy to maintain position

Terrestrials vs. Terrestrials vs. AquaticsAquatics

This section concerns the requirements for energy This section concerns the requirements for energy by aquatic animals, how energy is partitioned, by aquatic animals, how energy is partitioned, what it is used for and how it is measuredwhat it is used for and how it is measured

a major difference in nutrition between fish and a major difference in nutrition between fish and farm animals is the amount of energy required for farm animals is the amount of energy required for protein synthesisprotein synthesis

protein synthesis refers to the building of proteins protein synthesis refers to the building of proteins for tissue replacement, cell structure, enzymes, for tissue replacement, cell structure, enzymes, hormones, etc.hormones, etc.

fish/shrimp have a lower dietary energy fish/shrimp have a lower dietary energy requirementrequirement

Factors Affecting Factors Affecting Energy PartitioningEnergy Partitioning Factors either affect basal metabolic rate Factors either affect basal metabolic rate

(e.g., body size) or affect other changes(e.g., body size) or affect other changes those affecting BMR are the following:those affecting BMR are the following: body size:body size:non-linear, y = axnon-linear, y = axbb, for most , for most

physiological variables, b values usually physiological variables, b values usually range between 0.7 and 0.8range between 0.7 and 0.8

oxygen availability:oxygen availability: have conformers have conformers (linear) and non-conformers (constant (linear) and non-conformers (constant until stressed)until stressed)

OO22 Consumption, by Consumption, by SizeSize

(Fig. 2.1 from De Silva and Anderson)

Factors Affecting Factors Affecting Energy PartitioningEnergy Partitioning

temperature:temperature: most aquaculture species are most aquaculture species are poikilotherms, significant effect, acclimation required, poikilotherms, significant effect, acclimation required, aquaculture situation may mean rapid temp changesaquaculture situation may mean rapid temp changes

osmoregulation:osmoregulation: changes in salinity result in changes in salinity result in increased cost of energyincreased cost of energy

stress:stress: increased BMR resulting from heightened increased BMR resulting from heightened levels of waste, low oxygen, crowding, handling, levels of waste, low oxygen, crowding, handling, pollution, etc. (manifested by hypoglycemia)pollution, etc. (manifested by hypoglycemia)

cycling:cycling: various animal processes are cyclic in various animal processes are cyclic in nature (e.g., reproduction, migration)nature (e.g., reproduction, migration)

Factors Affecting Factors Affecting Energy PartitioningEnergy Partitioning Those factors Those factors notnot affecting BMR are: affecting BMR are: gonadal growth:gonadal growth: most energy diverted most energy diverted

from muscle growth into oogenesis, from muscle growth into oogenesis, deposition of lipid, can represent 30-40% deposition of lipid, can represent 30-40% of body weight, implications????of body weight, implications????

locomotion:locomotion: major part of energy major part of energy consumption, varies due to body shape, consumption, varies due to body shape, behavior and size, aquatic vs. terrestrial behavior and size, aquatic vs. terrestrial issuesissues

Another Index: Gross Another Index: Gross Conversion Efficiency Conversion Efficiency

((KK)) Referred to as “Referred to as “KK”, often used as an indicator of ”, often used as an indicator of

the bioenergetic physiology of fish under various the bioenergetic physiology of fish under various conditionsconditions

does not refer to an energy “budget”does not refer to an energy “budget” measures growth rate (SGR) relative to feed intake measures growth rate (SGR) relative to feed intake

over similar time periodsover similar time periods both factors are related to body size:both factors are related to body size:

SGR = (ln WtSGR = (ln Wtff-lnWt-lnWtii)/(T)/(Tff - T - Tii) x 100) x 100

RFI = (feed intake)/((0.5)(WtRFI = (feed intake)/((0.5)(Wtff -Wt -Wtii)(T)(Tff-T-Tii))))K = (SGR/RFI) x 100K = (SGR/RFI) x 100

Energy and GrowthEnergy and Growth Dietary excesses or deficiencies of useful energy can reduce growth Dietary excesses or deficiencies of useful energy can reduce growth

raterate this is because energy must be used for maintenance and voluntary this is because energy must be used for maintenance and voluntary

activity activity beforebefore it is used for growth it is used for growth

dietary protein will be used for energy when the diet is deficient in dietary protein will be used for energy when the diet is deficient in energy relative to proteinenergy relative to protein

when the diet contains excessive energy, feed intake is typically when the diet contains excessive energy, feed intake is typically reduced...fish don’t want to be fat????reduced...fish don’t want to be fat????

this also reduces intake of protein and other nutrients needed for this also reduces intake of protein and other nutrients needed for growthgrowth

Dietary Sources of Dietary Sources of Energy:Energy: proteinsproteins

Considerable interaction between major nutrient groups as Considerable interaction between major nutrient groups as energy sourcesenergy sources

protein can be used as an energy sourceprotein can be used as an energy source not typically used because of cost and use for protein not typically used because of cost and use for protein

synthesis (growth)synthesis (growth) optimal ratio of protein:energy is around 22 mg PRO/kJ (45 optimal ratio of protein:energy is around 22 mg PRO/kJ (45

kJ/g PRO; old info) kJ/g PRO; old info) species variation: 17 (59) for tilapia, 29 (35)for catfish, 29 species variation: 17 (59) for tilapia, 29 (35)for catfish, 29

(34) for mutton snapper (Watanabe, et al., 2001);(34) for mutton snapper (Watanabe, et al., 2001); digestibility variationdigestibility variation temperature variationtemperature variation

Energy and GrowthEnergy and Growth Consumption of diets with low protein to energy Consumption of diets with low protein to energy

ratios can lead to fat deposition (fatty acid ratios can lead to fat deposition (fatty acid synthetase)synthetase)

this is undesirable in food fish because it reduces this is undesirable in food fish because it reduces the dress-out yield and shortens shelf lifethe dress-out yield and shortens shelf life

undesirable in shrimp due to build-up in hepato- undesirable in shrimp due to build-up in hepato- pancreas (midgut), ultimately affecting cookingpancreas (midgut), ultimately affecting cooking

low protein:energy diets can be useful for low protein:energy diets can be useful for maturation animals, hatchery animals raised for maturation animals, hatchery animals raised for releaserelease

Energy Requirments of Energy Requirments of FishFish

Determining the energy requirement of fish Determining the energy requirement of fish has been a difficult task, slow in cominghas been a difficult task, slow in coming

most research has been devoted to most research has been devoted to identifying protein requirements, major identifying protein requirements, major minerals and vitaminsminerals and vitamins

in the past, feeds were formulated letting in the past, feeds were formulated letting energy values “float”energy values “float”

excess or deficiency of nutritional energy excess or deficiency of nutritional energy does not often lead to poor healthdoes not often lead to poor health

Energy Requirements of Energy Requirements of FishFish

Further, if feeds are formulated with practical Further, if feeds are formulated with practical feedstuffs (ingredients), their energy levels are not feedstuffs (ingredients), their energy levels are not likely to be offlikely to be off

it is really a matter of cost: protein is the most it is really a matter of cost: protein is the most expensive component of the diet, COH sources are expensive component of the diet, COH sources are cheap, why use protein as an energy source????cheap, why use protein as an energy source????

In terrestrials, feed is consumed to meet energy In terrestrials, feed is consumed to meet energy requirementsrequirements

thus, as energy level of the feed goes up, protein thus, as energy level of the feed goes up, protein level is also designed to go uplevel is also designed to go up

Energy Requirements of Energy Requirements of FishFish

This is because terrestrial animals are typically fed This is because terrestrial animals are typically fed on an on an ad libitumad libitum basis basis

fish, on the other hand, aren’t fed this wayfish, on the other hand, aren’t fed this way they are fed on a feed allowance basis (we they are fed on a feed allowance basis (we

estimate feed fed)estimate feed fed) various studies have shown that the digestible various studies have shown that the digestible

energy (DE) requirement for channel catfish and energy (DE) requirement for channel catfish and carp was around 8.3-9.7 kcal DE/100 g fish/daycarp was around 8.3-9.7 kcal DE/100 g fish/day

in terms of age, dietary level of DE and protein in terms of age, dietary level of DE and protein typically drop with agetypically drop with age

Protein, DE Protein, DE Requirements of Requirements of

Channel Catfish, by AgeChannel Catfish, by Age

From Lovell, 1989

Energy Requirements of Energy Requirements of FishFish

DE and protein requirements typically follow each other, DE and protein requirements typically follow each other, so the DE:P ratio (kcal/g) is fairly similar with age (if so the DE:P ratio (kcal/g) is fairly similar with age (if anything, a small increase)anything, a small increase)

this is partially due to the fact that fish grow faster when this is partially due to the fact that fish grow faster when young (higher tissue turnover rate, demand for protein)young (higher tissue turnover rate, demand for protein)

however, the influence of energy is stronger than that of however, the influence of energy is stronger than that of protein relative to growth (Cuzon and Guillaume, 1997)protein relative to growth (Cuzon and Guillaume, 1997)

energy levels in crustacean diets usually range similar energy levels in crustacean diets usually range similar to those of fishto those of fish

Energy Requirements of Energy Requirements of AquaticsAquatics

The objective in formulating diets for most The objective in formulating diets for most aquatic species is the same: finding a cheap aquatic species is the same: finding a cheap energy source that is digestible and will spare energy source that is digestible and will spare proteinprotein

glucose is not acceptable in that it causes high glucose is not acceptable in that it causes high blood sugar levels, poor growth, poor survivalblood sugar levels, poor growth, poor survival

complex dietary COH’s prove bettercomplex dietary COH’s prove better COH typically spares protein for growthCOH typically spares protein for growth increase in dietary energy tends to increase increase in dietary energy tends to increase

performance when a diet low in protein is fedperformance when a diet low in protein is fed

Energy ProblemsEnergy Problems

Lipids and carbohydrates are typical energy Lipids and carbohydrates are typical energy sources for crustaceanssources for crustaceans

unfortunately, crustaceans are unable to unfortunately, crustaceans are unable to tolerate diets having greater than 10% lipid tolerate diets having greater than 10% lipid (also hard to manufacture the feed!)(also hard to manufacture the feed!)

this means that the major energy source this means that the major energy source must be derived from COHmust be derived from COH

various COH are used to various degrees by various COH are used to various degrees by crustaceans, making it difficult to calculate crustaceans, making it difficult to calculate the true energy value of dietsthe true energy value of diets