Transcript Unit 1: Nutrients & Digestion

Unit 1: Nutrients &
Digestion
Chapter 1
Unit 1: Nutrients &
Digestion
Unit 1 Objectives:
Review the 6 basic nutrients and investigate
their function
Revisit the various digestive systems
Comprehend the functions of the digestive
anatomy of monogastrics and ruminants
Unit 1: Nutrients &
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Water
Cheapest, most abundant, most important
nutrient
Constitutes 45-85% of animal body weight
decreases with age
90-95% of blood
tissue is 70-90% water
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Three forms in the body
Intracellular
• muscle and skin
Extracellular
• interstitial fluids, lymph, cerebrospinal fluid, blood
plasma
Urinary and GI water
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Functions of Water
transportation of nutrients and excrement
chemical reactions
temperature regulation
shape
lubrication
Water Deficiencies
reduced feed intake
weight loss/dehydration
increased excretion of N and electrolytes
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Water sources
Drinking water
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temp/humidity affect consumption
dietary water affects consumption
productivity of the animal affects consumption
Water quality is crucial
Consumption rates
– Swine-2.5-5g/d
– Sheep-1-4g/d
– Cattle-8-16g/d (may be significantly more in
lactation)
– Horses-10-14g/d
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Water loss
urination
fecal
vaporization from lungs or through skin
sweat
Water absorption
Readily absorbed from virtually all sections of the
GI tract
• rumen, omasum, ileum, jejunum, cecum, LI
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Amount absorbed
• varies w/ species and diet
• indigestible dietary fiber can reduce absorption
• can be reduced by the amount of dietary pectins, toxins,
and stressors
Carbohydrates (CHO)
Consist of Carbon, Hydrogen, Oxygen
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Includes:
sugars
starches
cellulose
gums
CHO makes up 3/4 of plant dry wt.
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Classified by the number of sugar molecules
Monosaccharides
• glucose
– most important sugar in nutrition
– primary form used for energy
• fructose
Disaccharides
• sucrose
• maltose
• lactose
– milk sugar
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Polysaccharides
• starch
– principle sugar form in cereal grains
• cellulose
– 25-30% of fibrous plants
– most abundant CHO in nature
• hemicellulose
– main component of plant cell walls
– can only be degraded by microbial enzymes
– complex mixture of sugars
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Non-carbohydrate
• Lignin
– covers cellulose and hemicellulose to increase
rigidity of plant cell walls
– as level increases, digestibility decreases
– cannot be broken down by any animal or bacterial
enzyme
Functions
source of energy and heat
building blocks for other nutrients
stored by converting to fat
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Deficiencies
Ketosis
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common in animals requiring high amounts of energy
can have a “snowball” effect
increases breakdown of protein for energy
loss of BW
decreases milk production
can cause abortion
distinct smell of acetone
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Diabetes
• more common in humans
• insufficient insulin production by the pancreas
• can be genetically related
Digestion & Metabolism
Crude Fiber
• cellulose, hemicellulose, lignin
• Poorly digested
Nitrogen-Free Extract
• soluble sugars, starches
• readily digested
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Converted to Adenosine Triphosphate (ATP)
• the energy currency of the body
• drives all physiological processes that require energy
• 1 molecule of glucose will yield 38 ATP’s through various
oxidative pathways
Lipids
Can be soluble or insoluble depending on
what they’re mixed with
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Classification
Simple Lipids
• true fats
• waxes
Compound Lipids
• Lipoproteins
• Glycolipids
• LDL, VLDL, HDL
Derived Lipids
• Sterols
– Cholesterol
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• Fatty Acids
Essential Fatty Acids
• linoleic, linolenic acids
Protein
Main component of organs and soft
structures in the animal body
Dietary requirement is highest in young
animals
Proteins are very large molecules
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Protein structure
made up of very simple units called Amino Acids
(AA)
arrangement of AA in the chain and the length of
the chain determine the composition of the protein
22 AA are commonly found in proteins
• linked together by peptide bonds
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Levels of Protein structure
Primary Structure
• individual AA linked by peptide bonds to form a
polypeptide chain
Secondary Structure
• twisted polypeptide chain
• H bonds link helical structures together
Tertiary Structure
• helical structures fold into rigid layers
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Quaternary Structure
• several tertiary structures linked together
• very large proteins
Importance of protein structure
• biological activity of the protein related to the level of
the protein
• Denaturation
– loss of protein structure
– caused by heat
– loses biologic activity, but may increase digestibility
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• Maillard Reaction
– caused by excess heat
– excess heat may be caused by improper storage,
cooking, drying, etc.
– can severely decrease digestibility
Protein Terminology
True Protein
• made up only of AA
Nonprotein Nitrogen (NPN)
• not true protein compounds, but contain N, and can be
converted to protein
• ex.?
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Crude Protein
• total protein from true and NPN sources
• CP = %N x 6.25
Digestible Protein
• portion of CP that can be digested
• difference between fed protein and fecal protein
Essential AA
• essential to the animal, and must be supplied in the diet
b/c the animal cannot synthesize them fast enough to
meet the requirement
• PVT TIM HALL
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– Phenylalanine, Valine, Threonine, Tryptophan,
Isolecine, Methionine, Histidine, Arginine, Leucine,
Lysine
Functions
Basic structural units of the body
• collagen
• keratin
• blood proteins
Body Metabolism
• enzymes, hereditary transmission
• hormones, immune antibodies
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Deficiencies
reduced growth rate, and feed efficiency
infertility, fatty liver, lack of hormone/enzyme
production
deficiencies/imbalances in AA will decrease
production
Natural Sources
most feeds contain protein
quantity and quality of protein may be highly
variable
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Digestion & Metabolism
dietary proteins must be broken down to AA form
for absorption
• except in early postnatal mammals
in the stomach, proteins are broken down to:
• dipeptides
• tripeptides
• free AA
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Absorption of proteins
• Free AA
– absorbed by active transport (requires energy)
– occurs in the SI
• Di- & Tripeptides
– absorbed by mucosal cells in the SI in
– will still be changed to FAA
• Whole Proteins
– engulfed by mucosal cells
– only happens in newborn mammals (24-48 hrs.),
absorb antibodies from colostrum
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Minerals
total mineral content of plants often referred
to as Ash
constitutes 3-5% of animal body dry wt.
Classification
Macrominerals
• present/required in greater levels
• Ca, P, K, Mg, Cl, S, Na
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Microminerals
• present/required in small amounts
• Co, Cu, I, Fe, Mn, Mo, Se, Zn
Functions
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skeletal formation and maintenance
active in protein synthesis
oxygen transport
fluid balance, and pH
activates or components of enzyme systems
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Natural Sources
forage plants are good natural sources
may be somewhat variable
Digestion & Metabolism
absorbed in the SI in ionic form
active transport (Ca, P, Na) or diffusion
mineral absorption can vary due to:
• age of the animal
• form of the element, binding/chelation, excesses or
interactions of minerals
• pH of GI tract
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Vitamins
present and active in small amounts
essential for tissue development and immune
function
most cannot be synthesized, and must be
supplemented in the diet
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Classification
Fat-soluble
• Vitamins A, D, E, K
• regulate metabolism of structural units
• absorbed in the SI in the presence of fat
Water-soluble
• Thiamine, Riboflavin, Niacin, Biotin, Choline, Folic Acid,
B12, etc.
• concerned with the transfer of energy
• absorbed with intestinal water
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Digestion & Metabolism
little is known about vitamin digestion
most absorbed in the upper portion of the
intestine
• B12 is absorbed in the ileum
• water-soluble are readily absorbed
• fat-soluble vitamin absorption depends on fat absorption
(a slow process)
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Nutrients in Metabolism
Maintenance
Heat for temp regulation
energy for internal work
minimum movement
tissue repair
greatest requirement for energy
Growth
protein, energy and other nutrients required for
structural growth
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Especially critical when another bodily work is
ongoing
• lactation, work etc.
• growth will be sacrificed in the presence of another need
Work
mostly requires energy and water
Reproduction
minimal requirements
over or under-conditioning can reduce efficiency
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Lactation
very high nutritional demand
best to feed for lactation demand rather than
build up bodily stores
Fattening
high energy to protein ratio required
body will meet all other needs first
Called Nutrient Partitioning
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Requirements can vary
state of growth or age
size of animal
environment
heredity
disease
activity
degree of condition
ration imbalances
species
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Digestive Systems
terms to know:
Prehension-taking in feed/water
Mastication-chewing, reducing particle size
Deglutition-swallowing
Regurgitation-casting up of undigested material
Digestion-breakdown of feed to products for
absorption
• mechanical, chemical, or enzymatic activity
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Absorption-transfer of nutrients from GI to
blood/lymph
Anabolism-growth or building process
Catabolism-breakdown of structures
Metabolism-combination of anabolism &
catabolism processes in order to create energy
Excretion-elimination of wastes
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Monogastric Digestive System
Mouth
what is contained, and what is their functions?
Saliva
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water-moistens food, aids in taste
mucin-lubrication for swallowing
Bicarbonate salts-buffer to regulate pH
enzymes-amylase can begin breakdown of CHO (only in
some species)
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Esophagus
tube for transport from mouth to stomach
moved by muscular contractions called
Peristalsis
Stomach
Cardia-sphincter at junction of esophagus and
stomach that regulates passage into/out of
stomach
Esophageal Region-nongladular, surrounds the
cardia
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Cardiac Gland Region-produces mucus that
protects stomach lining
Fundic Gland Region-produces gastric secretions
needed to stimulate digestion
• hydrochloric acid, and enzymes
Pyloric Gland Region-mucus and proteolytic
enzymes
Pylorus-sphincter controlling passage of digesta
to intestine
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Functions
• feed storage
• physical breakdown of material by muscular movement
• secretion and regulation of “gastric juices”
– acid
– pepsinogen
– mucus
– rennin
material leaving stomach now called chyme
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Small Intestine
Duodenum
• receives secretions from pancreas, liver,
• active site of digestion
Jejunum
• active in nutrient absorption
Ileum
• also active in nutrient absorption
walls lined with villi and microville that increase
surface area for absorption
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Bile
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synthesized by the liver, stored in the gall bladder
emulsifies fats for absorption
activates pancreatic enzymes
much is recycled
Pancreatic Juice
• buffers
• digestive enzymes
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Large Intestine
Cecum
• size, and function can vary
Colon
• largest part
Rectum
• final section
Function
• water resorption
• can be storage of undigested nutrients
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• Can be site of bacterial fermentation
• limited site of nutrient absorption
Horse
Saliva
no enzymes
scratching from forages stimulates secretions
produce ~10g/d
Esophagus
50-60” long
one-way peristaltic movements
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Stomach
relatively small stomach, meals must be small
little muscular movement
Small Intestine
no gall bladder to store bile for secretion to SI
Large Intestine
60% of GI
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Cecum & Large Colon
• active bacterial population
• breakdown of cellulose and other CHO’s to Volatile Fatty
Acids (VFA) acetate, propionate, butyrate for use as
energy
• synthesize protein and water-soluble vits.
Small Colon
• primary site of water resorption
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Ruminant GI
Mouth
no upper incisors, upper and lower molars
lateral chewing for shredding of forages
Saliva
• relatively continuous production, more when ruminating
or eating
• cattle >12 g/d, sheep >2g/d
• no enzymes, but sources of N(urea), P, Na
• highly buffered
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Stomach
Reticulum (honeycomb)
• esophageal opening of common to both reticulum and
rumen
• mucus lined walls, no enzyme secretions
• moved feed to rumen, omasum
• catches any foreign matter
• moves feed up esophagus during regurgitation
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Rumen
• very large, muscular compartment
• contains papillae (shag carpet) to increase surface area
• functions
– storage
– soaking
– physical breakdown & mixing
• very effective fermentation chamber
– warm, moist, anaerobic, ideal pH
– 25-50b bacteria/mL of rumen fluid
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– Production of water-soluble vits.
– Production of AA’s & proteins
– rumen bacteria also serve as a valuable source of
dietary protein & AA’s
– rumen bacteria also can digest cellulose & CHO’s to
produce VFA’s for use as energy
• fully functional by 6-9 wks. of age
Omasum
• spherical and very muscular
• works to reduce particle size of feed before it enters the
rest of the GI
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Abomasum
• first glandular portion of the ruminant GI
• very similar to the stomach of the nonruminant
Small and Large Intestine
very similar to the nonruminant
Specialties of the Ruminant GI
Esophageal Groove
• can direct ingesta directly to the Omasum
• doesn’t appear to be functional in the adult
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Rumination
• allows animal to ingest a lot of feed, then chew at a
later time
• process:
– regurgitation
– remastication
– resalivation
– reswallowing
• stimulated by:
– particle size
– reverse-peristaltic contraction of the
rumen/reticulum
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• Cud is mostly forage
• cattle should ruminate ~8hrs./d
Eructation
• bacterial fermentation produces large amounts of gas
• rumen contractions force gas forward and down to the
esophagus
• bloat occurs when the gas cannot escape
Nutrient Digestion
converting feed products into forms that can
be absorbed from the GI
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Five major areas where digestive enzymes
are secreted into the GI
Mouth (Saliva)
Stomach (Gastric)
Pancreas (Duodenum & upper SI)
Liver
Intestine
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Nutrient Absorption Summary
nutrient absorption moves digestion products
from GI to the blood or lymph system
occurs by osmosis through semipermeable
membranes
Diffusion
• molecules move from regions of high concentration to
low
Active Transport
movement of molecules from one region to
another w/ the expenditure of energy
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Occurs in the SI & LI primarily
much VFA absorption in the rumen
greatly aided by GI villi
Absorption in the Duodenum & Jejunum
CHO
FAA, di & tripeptides
fatty acids
minerals
vitamins
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