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Carbohydrates

Carbohydrates. From: Lovell; D’Abramo et al., and Guillaume et al. Carbohydrate Structure. Basic chemical structure consists of sugar units, often repeating ones. Contain: C, H, O (abbreviated CHO’s) Exist as straight-chain, or ringed structures. Glucose Structure. O C-H

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Carbohydrates

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

  2. Carbohydrate Structure • Basic chemical structure consists of sugar units, often repeating ones. • Contain: C, H, O (abbreviated CHO’s) • Exist as straight-chain, or ringed structures

  3. Glucose Structure O C-H H- C-OH HO-C-H H-C-OH H-C-OH CH2OH CH2OH O H H OH H OH HO H OH Haworth perspective

  4. Carbohydrate Classification • Usually by the number of sugar units in the molecule: • monosaccharides (glucose) • disaccharides (2 units) • maltose (2 glucose units) • sucrose (glucose + fructose) • polysaccharides (long chain polymers of monosaccharides • most important polysaccharides to animals are starch and cellulose

  5. Starch and Cellulose • Starch contains -D-glucose linkage • Cellulose has a -D-glucose linkage • Animals store starch as glycogen (muscles), peeled off by enzymes when needed • Cellulose (plants) largely indigestible to monogastrics (i.e. fish and us!) • Must have enzyme, “cellulase”

  6. Starch and Cellulose CH2OH CH2OH O O H H H H starch OH H OH H O O O H OH H OH CH2OH CH2OH H O O H O O O OH H OH H H H cellulose H OH H OH

  7. Carbohydrates in Fish and Shrimp Diets • CHOs are non-essential dietary nutrients for fish and shrimp, but still valuable: • They’re cheap dietary energy for noncarnivorous fish and shrimp species. • Can spare protein for growth instead of energy provision. • Help us manufacture water-stable diets (binders, ie. gelatinized starch, alginates, gums). • Can increase feed palatability and reduce the dust content of finished feeds (ie. cane or beet molasses).

  8. What regulates the CHO inclusion in practical feeds? • Often its species specific, but many species digest complex carbs, better than simple ones. • ADC (average digestiblity coefficient) of carb. is also important. • Pre-treating carbs also improves digestion.

  9. Table 8.3 Digestibilty data for CHOs* in trout Effect of nature of ingredient %ADC Raw wheat 54 corn 33 Treated wheat 96 *Generally, we find that as we feed more carbs (starch) the ADC goes down while feed intake increases, meaning that too many carbs are bad.

  10. Table 8.3 Digestibilty data for CHOs in trout Effect of nature of ingredient %ADC Water Temp. Raw (>30% inclusion) 8ºC 31 18ºC 41 Gelatinized (>30% inclusion) 8ºC 64 18ºC 75

  11. Table 8.4: Guillaume, et al. Suggested max carbs in various fish spp. Spp. % Dietary Carb Salmonids (trout, salmon, char) 25-30 Cyprinids (carp, loach, minnows) 40-45 Siluriformes (catfish) 30-35 Cichlid (tilapia) 35-40 Sea bass 25-30 Red Drum 20-25 Yellowtail 10-15

  12. Fiber? • Some fiber is good. Too much is bad. • Much more than 4% dietary fiber (insouluble) generally results in: • shortened gastric passage rates • lower nutrient absorption • fouling of water quality from excessive fecal excretion.

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