CarbohydratesCarbohydrates

From: Lovell; D’Abramo et al., and From: Lovell; D’Abramo et al., and Guillaume et al. Guillaume et al.

Carbohydrate StructureCarbohydrate Structure

Basic chemical structure consists of Basic chemical structure consists of sugar units, often repeating ones.sugar units, often repeating ones.

Contain: C, H, O (abbreviated Contain: C, H, O (abbreviated CHO’s)CHO’s)

Exist as straight-chain, or ringed Exist as straight-chain, or ringed structuresstructures

Glucose StructureGlucose Structure

O

C-H

H- C-OH

HO-C-H

H-C-OH

H-C-OH

CH2OH

CH2OH

OH

HO

OH

H

H

OH

H

OH

Haworth perspective

Carbohydrate ClassificationCarbohydrate Classification

Usually by the number of sugar units in the Usually by the number of sugar units in the molecule:molecule:– monosaccharidesmonosaccharides (glucose) (glucose)– disaccharidesdisaccharides (2 units) (2 units)

maltose (2 glucose units)maltose (2 glucose units) sucrose (glucose + fructose)sucrose (glucose + fructose)

– polysaccharidespolysaccharides (long chain polymers of (long chain polymers of monosaccharidesmonosaccharides

– most important polysaccharides to most important polysaccharides to animals are starch and celluloseanimals are starch and cellulose

Starch and CelluloseStarch and Cellulose

Starch contains Starch contains -D-glucose linkage-D-glucose linkage Cellulose has a Cellulose has a -D-glucose linkage-D-glucose linkage Animals store starch as Animals store starch as glycogenglycogen

(muscles), peeled off by enzymes (muscles), peeled off by enzymes when neededwhen needed

Cellulose (plants) largely indigestible Cellulose (plants) largely indigestible to monogastrics (i.e. fish and us!)to monogastrics (i.e. fish and us!)

Must have enzyme, “Must have enzyme, “cellulasecellulase””

Starch Starch and and CelluloseCelluloseCH2OH

OH

OH

H

H

OH

H

CH2OH

OH

OH

H

H

OH

H

OO O

CH2OH

OH

OH

H

H

OH

CH2OH

O

OH

H

H

OH

H

OO

H

H

O

starch

cellulose

Carbohydrates in Fish and Carbohydrates in Fish and Shrimp DietsShrimp Diets

CHOs are non-essential dietary nutrients for fish and CHOs are non-essential dietary nutrients for fish and shrimp, but still valuable:shrimp, but still valuable:

They’re cheap dietary energy for noncarnivorous fish They’re cheap dietary energy for noncarnivorous fish and shrimp species.and shrimp species.

Can spare protein for growth instead of energy Can spare protein for growth instead of energy provision.provision.

Help us manufacture water-stable diets (binders, ie. Help us manufacture water-stable diets (binders, ie. gelatinized starch, alginates, gums).gelatinized starch, alginates, gums).

Can increase feed palatability and reduce the dust Can increase feed palatability and reduce the dust content of finished feeds (ie. cane or beet molasses).content of finished feeds (ie. cane or beet molasses).

What regulates the CHO What regulates the CHO inclusion in practical feeds?inclusion in practical feeds?

Often its species specific, but many Often its species specific, but many species digest complex carbs, better species digest complex carbs, better than simple ones.than simple ones.

ADC (average digestiblity coefficient) of ADC (average digestiblity coefficient) of carb. is also important.carb. is also important.

Pre-treating carbs also improves Pre-treating carbs also improves digestion.digestion.

Table 8.3 Digestibilty data Table 8.3 Digestibilty data for CHOs* in troutfor CHOs* in trout

Effect of nature of ingredientEffect of nature of ingredient %ADC%ADCRawRawwheatwheat 5454corncorn 3333

TreatedTreatedwheatwheat 9696

*Generally, we find that as we feed more carbs (starch) *Generally, we find that as we feed more carbs (starch) the ADC goes down while feed intake increases, the ADC goes down while feed intake increases, meaning that too many carbs are bad.meaning that too many carbs are bad.

Table 8.3 Digestibilty data Table 8.3 Digestibilty data for CHOs in troutfor CHOs in trout

Effect of nature of ingredientEffect of nature of ingredient %ADC%ADC

Water Temp.Water Temp.

Raw (>30% inclusion)Raw (>30% inclusion)

88ººCC 3131

1818ººCC 4141

Gelatinized (>30% inclusion)Gelatinized (>30% inclusion)

88ººCC 6464

1818ººCC 7575

Table 8.4: Guillaume, et Table 8.4: Guillaume, et al.al.

Suggested max carbs in various fish spp.Suggested max carbs in various fish spp.

Spp.Spp. % Dietary Carb% Dietary Carb

Salmonids (trout, salmon, char)Salmonids (trout, salmon, char) 25-3025-30

Cyprinids (carp, loach, minnows)Cyprinids (carp, loach, minnows)40-4540-45

Siluriformes (catfish)Siluriformes (catfish) 30-3530-35

Cichlid (tilapia)Cichlid (tilapia) 35-4035-40

Sea bass Sea bass 25-3025-30

Red DrumRed Drum 20-2520-25

YellowtailYellowtail 10-1510-15

Fiber?Fiber?

Some fiber is good. Too much is Some fiber is good. Too much is bad.bad.

Much more than 4% dietary fiber Much more than 4% dietary fiber (insouluble) generally results in:(insouluble) generally results in:– shortened gastric passage ratesshortened gastric passage rates– lower nutrient absorptionlower nutrient absorption– fouling of water quality from fouling of water quality from

excessive fecal excretion.excessive fecal excretion.