Animal nutrition - carbohydrates Flashcards
Percentage of Energy contribution from carbohydrates in farm animal nutrition is
70…80%
what fractions of DM are carbohydrates?
crude fibre
▪ plant cell wall substances
(not all of crude fiber is carbs though)
nitrogen-free extracts
▪ starch, sugars etc.
Classification according to van Soest system:
– Neutral detergent fibre (NDF)
– Acid detergent fibre (ADF)
name 3 Neutral detergent fibre (NDF) compounds
▪ Hemicellulose + Cellulose + Lignin
name 2 Acid detergent fibre (ADF) compounds
▪ Cellulose + Lignin
Classification of carbs in pig feeding and in human nutrition:
– mono- and disaccharides
– starch containing polysaccharides
– starch not containing polysaccharides → ration fibre
This distribution arises because monogastric animals can digest only starch (α-1,4 and α-1,6 glycosidic bond) of the polysaccharides.
Starch not containing polysaccharides contain different β-glycosidic bonds, which are not digestible due to lack of endogenous enzymes.
Classification of carbs in ruminant feeding:
– structural carbohydrates -> effective fibre
– non-structural carbohydrates
what are structural carbohydrates
▪ plant cell wall substances (cellulose, hemicellulose, lignin, but not pectin), most are hydrolysed by bacterial enzymes and ensure the necessary rumen environment (lignin is not)
what are non-structural carbohydrates
▪ mono- and disaccharides, starch
In nature, the most common Monosaccharides are (3)
– trioses – organism metabolism intermediates, amount in feeds is low (glycerol and
dihydroxyacetone)
– pentoses - arabinose, xylose, ribose
– hexoses - glucose, fructose, galactose, mannose
Monosaccharides chemically contain how many C atoms?
3, 4, 5, 6 or 7 C atoms
the main component of plant polysaccharides
the pentose arabinose
the main monosaccharide in hemicellulose
the pentose xylose
the pentose ribose is found in (3)
RNA, coenzymes, B12
monosaccharide Hexoses include (4)
– glucose
– fructose
- galactose
- mannose
– glucose also known as (2)
▪ grape sugar or blood sugar
▪ di- and polysaccharides, glycogen
– fructose also known as (1)
▪ fruit sugar, sweetest CH
– galactose found in
▪ in the composition of lactose
– mannose found in (1)
▪ component of glycoproteins
Disaccharides are formed when two monosaccharides are bound together (dehydration reaction), which leads to the loss of H2O and formation of a
glycosidic bond (α or β)
An alpha-glycosidic bond is formed when both carbons have the same stereochemistry, whereas a beta-glycosidic bond occurs when the two carbons have different stereochemistry.
Humans lack digestive enzymes capable of hydrolyzing most β-glycosidic bonds, which explains why amylose, a glucose polymer with α-1,4 glycosidic bonds, is digestible by human enzymes, while cellulose, a glucose polymer with β-1,4 glycosidic bonds, is indigestible.
what breaks a glycosidic bond and leads to
hydrolysis breaks the glycosidic bond and H2O is incorporated
Sucrose is
a Disaccharide composed of glucose + fructose, found in
– table/cane/beet sugar
– vegetative parts of plants
– sugar beet, fodder sugar beet
Lactose is
a Disaccharide composed of glucose + galactose, found in
– milk sugar, milk-based feeds
Maltose is
a Disaccharide called malt sugar,
composed of glucose + glucose,
is a starch hydrolysis product
found in
– more in germinating grains
how to tell a (α from β) glycosidic bond
1,4 alpha glycosidic bonds are formed when the OH on the carbon-1 is below the glucose ring; while 1,4 beta glycosidic bonds are formed when the OH is above the plane.
“Alpha linkage has the oxygen (on the aldehyde or ketone) below the ring and the beta has it above the ring. “
Oligosaccharides contain
3…10 monosaccharide residues