ANSC 303 CHO
Carbohydrates
2 types of CHO
Structural carbohydrates (SCHO): fiber; not hydrolyzed by mammalian enzymes; hydrolyzed by microbial enzymes
Cellulose: hay or grass; glucose
Nonstructural carbohydrates (NCHO): starches & sugars; hydrolyzed by both mammalian and microbial enzymes
starch; corn; glucose
Monosaccharides: 1 sugar; glucose, galactose, fructose
abs by the enterocytes
fermented by the microbes
Disaccharides: 2 sugars; linked by glycosidic bond
lactose: milk sugar; glucose and galactose ME BE
sucrose: table sugar; glucose and fructose ME BE
maltose: product of starch digestion; glucose and glucose ME BE
cellobiose: product of cellulose digestion; glucose and glucose BE
Polysaccharide: many sugars; linked by glycosidic bonds (n-1)
Starch: homopolymer of glucose; \alpha glycosidic bonds ME BE
storage polysaccharide
glycogen: storage polysaccharide; in muscle and liver
Cellulose: homopolymer of glucose; \beta glycosidic bonds BE
structural polysaccharide
Hemicellulose: heteropolymer; many different sugars BE
structural polysaccharide
Pectin: heteropolymer; many different sugars BE
“fiber”: highly digestible
Not a CHO
Lignin is not a CHO
It is part of the plant cell wall: associate with cellulose
Increased [lignin]= decreased digestibility of cellulose
Lignin is 100% indigestible: 0% digestible
Digestibility %= (intake-feces/intake) x 100%
Two types of Starch:
Amylose: \alpha 1,4 linkages; straight chain of ~ 100 glucose molecules
Amylopectin: \alpha 1,4 and 1,6 linkages; 1-6= branch points; 1,000-10,000 glucose molecules; structurally similar to glycogen
Maltose: linked by \alpha 1-4 glycosidic bond (mammalian and microbial enzymes can hydrolyze) + 1 H2O = 2 glucose
ME absorbs 2 glucose and \ge 68 ATP
BE ferments 2 glucose \le 50 ATP
Cellobiose: linked by \beta 1-4 glycosidic bon (only digestible by microbial enzymes) + 1 HO = 2 glucose
BE ferments 2 glucose \le 50 ATP
Mammalian Digestion of NCHO
Polysaccharide (starch) + H2O and ME from the small intestine = monosaccharide
Disaccharide: glucose, galactose, fructose is absorbed by enterocytes in the small intestine
Glucose, galactose, fructose go to the body which is made into adipose (fat), glycogen, and energy (ATP)
Mouth decreases particle size
Salivary amylase (pig, hore) hydrolyzes \alpha 1,4 bonds
Stomach decreases in pH to deactivate salivary amylase
Small intestine is where most of mammalian NCHO digestion occurs
All of glucose, galactose, and fructose are absorbed
Increased pH to optimize enzyme activity
Pancreatic \alpha amylase: hydrolyze \alpha 1,4 bonds
Amylose + H2O + Pancreatic \alpha amylase = maltose + maltotriose
Amylopectin + H2O + Pancreatic \alpha amylase = maltose + maltotriose + isomaltose (with 1,6 linkages)
Brush Border Enzymes (BBE): enzymes produced by the enterocytes
Maltase: Maltose + H2O = 2 glucose
Isomaltase: Isomlatose + H2O = 2 glucose
Maltotriose + 2H2O + maltase & isomaltase = 3 glucose
Glucoamylase: hydrolyzes 1 glucose molecule from starch
Amylose or amylopectin + H2O + glucoamylase = 1 glucose
Sucrase: Sucrose + H2O = glucose + fructose
Lactase: Lactose + H2O = glucose + fructose (usually decreases after weaning)
Phlorizin hydrolase: hydrolyzes sugars bound to lipids
98% of blood from the GIT goes to the liver
Galactose and fructose + biochemistry = glucose
Insulin: decreases blood [glucose]; comes from the pancreas; \beta cells; islets of langerhans
Produced in response to increases [glucose]
Body’s response to insulin:
Increased protein synthesis
Increased glycogen synthesis (liver and muscle)(GLUT4 to absorb glucose) (muscle and adipose to absorb glucose)
Increased fat synthesis (GLUT4 to absorb glucose) (muscle and adipose to absorb glucose)
Decreased glyconeogenesis: creation of glucose (amino acids)
The blood vessel containing glucose and insulin will use GLUT4 to transport glucose into the adipocyte. When in the adipocyte, glucose is ready for fat synthesis
After translocation, glucose is absorbed and blood [glucose] decreases
In a muscle cell: GLUT4 also translocates in response to insulin and glucose in absorbed. This leads to blood [glucose] and increased glycogen synthesis.
NCHO Digestion in Non Ruminants
Starch becomes amylose, amylopectin, lactose, and sucrose
In the lumen of the small intestine, pancreatic \alpha amylase turns amylose and amylopectin into maltose
In the lumen of the small intestine, pancreatic \alpha amylase turns amylose and amylopectin into maltotriose
In the lumen of the small intestine, pancreatic \alpha amylase turns amylopectin isomaltase
In the lumen of the small intestine, glucoamylase turns amylopectin into glucose
In the lumen of the small intestine, lactase turns lactose into glucose
In the lumen of the small intestine, pancreatic \alpha amylase turns amylose into glucose
In the lumen of the small intestine, lactase turns lactose into galactose
In the lumen of the small intestine, sucrase turns sucrose into fructose
In the lumen of the small intestine, maltase turns maltose and maltotriose into glucose
In the lumen of the small intestine, isomaltase turns isomaltose into glucose
Glucose and galactose go through the SGLT1 to the enterocyte
Fructose goes through GLUT5 to the enterocyte
The enterocyte uses GLUT2 to transport to the blood which goes to the liver
Biochemistry occurs to the glucose, galactose, and fructose in the blood to become glucose which goes back to the blood
GLUT1-3 is insulin independent
GLUT4 (muscle and adipose) is insulin dependent
When fasted (low blood [glucose]), glucose in the blood vessel has no way of getting to the adipocyte
When high blood [glucose], glucose will use GLUT4 to transport into the adipocyte to get glucose ready for fat synthesis
In type I diabetes (no insulin production) glucose cannot go into the adipocyte
this is due to genetics and immune system
In type II diabetes (insulin but no signal), there is glucose in the blood but no way to enter the adipocyte
It is increasing in young people
Caused by genetics and weight/exercise
Glucagon: made in the pancreas; \alpha cells; produced in response to low blood [glucose]
this causes increased gluconeogenesis: glucose from amino acids
increased glycogen breakdown: release glucose from muscle and liver
decreased protein synthesis:
amino acids are being used for glucose synthesis
less energy available for protein synthesis
decreased fat synthesis: less energy available (less glucose)
Products of Fermentation
Acetate
# VFA/glucose: 2
Microbial ATP: 4
CO2: 1
CH4 (hydrogen sink) (energy loss): 1
CH3COOH
% of glucose energy available to the mammal: 62%
Portion of VFAs: 60%
Increased with increased SCHO
Decreased with increased NCHO
Uses by mammal: Energy ATP
SQ fat/ milk fat
Propionate (hydrogen sink)
# VFA/glucose: 2
Microbial ATP: 1-4
CO2: 0
CH4 (hydrogen sink) (energy loss): prevents 0.5 CH4
Ch3Ch2COOH
% of glucose energy available to the mammal: 109%
Portion of VFAs: 30%
Decreased with increased SCHO
Increased with decreased NCHO
Uses by mammal: Energy ATP
Glyconeogenic/marbling
Butyrate
# VFA/glucose: 1
Microbial ATP: 3
CO2: 1.5
CH4 (hydrogen sink) (energy loss): 0.5
CH3CH2CH2COOH
% of glucose energy available to the mammal: 78%
Portion of VFAs: 10% (disaccharides)
Increased CH4 loss and decreased energy to cow
Decreased CH4 loss and increased energy to cow
Uses by mammal: Energy ATP
Epitelial tissue
Hydrogen sink: a molecule where H2 is deposited
allows microbial fermentation to continue
In real life propionate is never greater than acetate
Amylolytic Bacteria
Amylases:
\alpha amylase
endoenzyme; hydrolyzes \alpha bonds on the inside of the molecule; oligosaccharides
\beta amylase
exoenzyme; produces maltose, maltotriose and isomaltose
Glucoamylase: produces glucose from starch
Maltase: maltose and maltotriose
Isomaltase: isomaltose and maltotriose
Pullulanase: hydrolyzes 1,6 bonds; debranching enzyme
\alpha amylase turns starch into oligosaccharides
\beta amylase turns starch into maltose, isomaltose, maltotriose
\beta amylase and pullulanse turns oligosaccharides into maltose, isomaltose, maltotriose
Glucoamylase turns starch into glucose
maltase turns maltose into glucose
isomaltase turns isomaltose into glucose
maltase and isomaltase turns maltotriose into glucose
this glucose is turned into VFA, CO2, CH4 (will have increased proportion of propionate and decreased CH4)
Cellulolytic Bacteria
Cellulase complex: optimal pH of 6.5-6.8
Glucanases
Exoglucanase: produces 1 glucose from cellulos
Endoglucanase: produces oligosaccharides from cellulose
Cellulodextrinase: produces 1 glucose from cellulose
Cellobiohydrolase: produces cellobiose from oligosaccharides
Cellobiosidase: produces cellobiose from oligosaccharides
Cellobiase: produces 2 glucose molecules from cellobiose
Endoglucanase turns cellulose into dissacharides
Exoglucanase and cellulodextrinase turn cellulose into glucose
Cellulobiohydrolase turns disaccharides into cellobiose
Cellobiose turns into glucose
Glucose turns into VFA, CO2, CH4
Ruminal Responses to Starch
Increased VFA production, increased MCP production, and increased MPL production
NCHO are more digestible and fermentable
Increased ATP available to the microbes
Decreased acetate and propionate
because amylolytic microbes produce more propionate
good because it increases glucose and energy supplied to the mammal
Decreased CH4
because propionate is hydrogen sink
good because CH4 is a greenhouse gas and a loss of energy
Decreased ruminal pH
Decrease in SCHO digestion
Reticulorumen
Lots of papillae; increased surface area
honeycomb appearance
stratified squamous epithelium
2 layers of muscle
Deep (circular): thick fibers that run in a circular direction
Superficial: thin fibers run cranio-caudally
Reticulorumen Stratification
free gas
hay mat: wet grass
changes size based on diet
forage: large hay mat
grain: hay mat basically nonexistent
liquid slurry
fermentation
grain
small particle
Ruminal acidosis
rapid production and accumulation of lactic acid
results in a pH of <5.5
commonly seen in cattle that have just arrived at the feedlot: because of dietary shift from SCHO to NCHO
Preventing ruminal acidosis
maintain adequate dietary SCHO intake
difficult to manage
decrease gain
transition from SCHO to grain (NCHO)
~28 days
allows ruminal microbes time to adapt
Ionophores-rumensin
regulate intake
increase number of meals and decrease meal size
selects for a more favorable fermentation/micrbial population
decreases lactate
\le