4 – CHOs Flashcards
1
Q
What are the 2 groups of CHOs?
A
- Glycemic CHOs
a. Glucose, sucrose, fructose, lactose (monosaccharides and disaccharides)
b. Starch - Fiber=can’t be digested by animal
a. Cellulose
b. Hemicellulose
c. Etc.
2
Q
What is starch?
A
- Major storage CHO in higher plants
- Polymers of glucose
- 2 types
3
Q
What are the 2 types of starch?
A
- Amylose
- Amylopectin
4
Q
Amylose
A
- Linear polymer of glucose
- Glucose residues attached by alpha-1-4 linkages
- Helical structure
- *Slowly digested b/c helix is resistant to enzyme degradation
5
Q
Amylopectin
A
- Branched polymer of glucose alpha-1-4 and alpha-1-6
- Open structure=accessible to enzyme degradation
o RAPIDLY digested
6
Q
Starches in feed
A
- Starch rich feeds=cereals and some pulse crops
- Amylose content varies with plant species
- Up to 70% dietary energy comes from starch in animal feeds
7
Q
Which feeds are slowly digestible?
A
- Peas: 60-88% amylose
- Lentil: 32-63% amylose
- *lower glycemic index
o May be able to increase GI by cooking it to partially OPEN up structure
8
Q
Which feeds are more quickly digested and good form production animals?
A
- Corn: 25-30% amylose
- Wheat: 20-30% amylose
- *higher glycemic index=huge amount of readily available energy
- *more amylopectin=anabolic effect and weight gain
9
Q
GI and amylose vs. amylopectin
A
- Connected
- Higher GI if more amylopectin
o Ex. corn and high glycemic index barley
o *higher N utilization - Lower GI if more amylose
o Ex. low glycemic index barley
o *lower N utilization=reduced protein deposition
10
Q
What is fibre?
A
- Act as structural CHO in plants
o Stem, husk of seeds - *anything that is NOT READILY digestible
- Soluble vs. insoluble in the gut
11
Q
What are some examples of soluble fibres?
A
- Some hemicelluloses
- Pectin: in fruit
- Gums
- Beta-glucans: grounded oats
- *what our microbiome can handle
12
Q
What are some examples of insoluble fibres?
A
- Lignin
- Cellulose
- Some hemicelluloses
- *so complicated it can’t even hydrate in the gut
o If not a ruminant=pooped out pretty much fully intact - **bulk forming fiber=bulks up the feces
13
Q
What is cellulose?
A
- Long, linear polymer repeating glucose units in beta-1-4 linkage
- Insoluble in water
- Indigestible by vertebrate enzymes
14
Q
What is hemicellulose?
A
- Heterogenous groups of polysaccharide substances
- Sugars in back bone and side chains
o Xylose, mannose, galactose: backbone
o Arabinose, glucuronic acid, galactose: side chains - Beta-1-4, alpha-1-2 linkages
o Slightly more digestible then cellulose, but still difficult
15
Q
What is lignin?
A
- Highly-branched poly-phenolic (-OH groups added) polymer composed of phenol units with strong bonding
- Indigestible by mammalian and microbial enzymes (except termites)
- Plant content increases as plant matures (ex. wood)
16
Q
What is pectin?
A
- Complex groups of polysaccharides=galacturonoglycans
- Backbone=alpha-1-4 linked galacturonic acid untis
o Sugar (xylose, galactose, etc.) side chains - Microbial fermentation
17
Q
What are beta-glucans?
A
- Homo-polymers of glucopyranose units with beta-1-4, beta-1-3 linkages
- Water soluble, highly fermentable
o Viscous intestinal fluid interferes with digestion in poultry
o Beta-glucanase added to poultry diets containing barley or OATS - Used commercially as functional fibre
o Reduced cholesterol and improves postprandial [glucose] - *improves longevity (ex. feed to dogs)
18
Q
What are soluble xylans?
A
- Beta-linked xylose backbone, arabinose side chains
o Causes poor nutrient digestibility in poultry - Rye and wheat are major sources
o Xylanase added to poultry diets
19
Q
Structure of fibre in forages
A
- Lots of cellulose
- Some lignin: will increase as it ages
- Some hemicellulose
- *very tightly packed
20
Q
Digestion of fiber: vertebrates vs. microorganisms
A
- Vertebrates do NOT have digestive enzymes required to break down fibre
- Microorganisms can digest fibre via fermentation
