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Animal Nutrition
Chapter 41
The Need to Feed

Animals are
 Herbivores
 Carnivores
 omnivores
Food and Nutrients
Food Any substance, either raw or
processed which is meant for human
consumption
 Nutrients The components of food
that the body can use for growth,
repair and energy

Homeostatic Regulation
Glucose level
rises, insulin is
secreted
Glucagon
promotes the
breakdown of
glycogen blood
glucose levels
rise
Insulintransport of
glucoseliver & muscle
store glucose lblood
levels drop
Glucose level
drops glucagon
is made to
oppose the
effect of insulin
Appetite Regulating Hormones
PYY is an appetite
suppressant
 Ghrelin triggers hunger
 Insulin suppresses
appetite
 Leptin suppresses
appetite

Figure 41.2 A ravenous rodent
Obesity related to leptin.
Types of Nutrients
Carbohydrates
 Proteins
 Fats
 Vitamins
 Minerals
 Water
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Essential Nutrients
Essential AA
 Essential fatty acids
 Vitamins
 Minerals
Undernourishment vs. malnutrition
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Essential Amino Acids
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Animals require 20
AA
Can synthesize most
8 are essential, must
obtain from food
How do vegetarians
get all essential AA?
Essential Fatty Acids
Need to obtain from food
 Unsaturated FA
 Linoleic Acid
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Essential Nutrients

What happens if an animal’s diet is
missing an essential nutrient?
 Deficiency
Diseases
scurvy — vitamin C (collagen production)
 rickets — vitamin D (calcium absorption)
 blindness — vitamin A (retinol production)
 anemia — vitamin B12 (coenzyme function)
 kwashiorkor — protein
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Vitamin Requirements of Humans: Water-Soluble
Vitamins
Vitamin Requirements of Humans: Fat-Soluble
Vitamins
Mineral Requirements
Intracellular Digestion in Paramecium
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Digestion occurs in
specialized
compartments
Intracellular
digestion occurs in
protists and sponges
Gastrovascular Cavities and Extracellular
Digestion

Gastrovascular
cavities do both
digestion and
distribution
 Ex.
Cnidarians,
platyhelminthes (flat
worms)

Two-way digestion
One Way Digestive Tracts
Stages of Food Processing
Ingestion: eating or drinking
Digestion : Breaking food into smaller
molecules
1.
2.
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•
3.
4.
Mechanical
Chemical (Enzymes)
Absorption: nutrient molecules enter
blood, the circulatory system transports
it through out the body
Elimination: undigested material passes
out of the body
The Digestive System
 Functions
like a series of tube like
organs which pass through the body
from the mouth to the anus
Alimentary Canal
 Alimentary Canal can be about 30’
long
 Accessory organs Pancreas, Liver,
Gallbladder secrete enzymes that
are released into the food tube
Digestion in the Mouth
It all begins in the mouth . . .
 Teeth,
tongue
 Salivary glands
Mucus
Amylase
 Only carbohydrates are digested
here
Swallowing and Peristalisis
Glottis and Epiglottis
From mouth to stomach: the swallowing reflex and esophageal peristalsis (Layer
2)
From mouth to stomach: the swallowing reflex and esophageal peristalsis (Layer
1)
Peristalsis
Rhythmic muscular contractions propel a
bolus of food
The human digestive system
Digestion in the Stomach
Muscular organ
 Acts as a
reservoir where
food is prepared
for digestion in
the SI
 Produces Gastric
Juices

Stomach Functions
Food Storage
2. Mechanical Digestion
3. Chemical Digestion
Secretions:
1. Mucus
2. EnzymePepsinogen
3. HCL
1.
CHYME semi-fluid food
mixture leaves.
Protection from Self-Digestion
 Protective
lining
 Main enzyme -Pepsin is
inactive Pepsinogen when
secreted
Digestion in the Stomach
Pepsinogen Comes in contact with HCl
Pepsin
 Pepsin converts proteins into peptones
 Acidity of Gastric juices kills some
bacteria that enters with food
 Gastric Juices  stimulated by
psychological and chemical means
 Peristaltic process of moving chyme into
the SI takes place for 6hrs

Small Intestine
Digestion in the Small Intestine
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Main stage of Digestion
As chyme enters the SI secretes juices that are
alkaline and neutralizes the acidity
SI maltase,lactase,sucrase breaks
disaccharides
Liver secretes bile emulsifies fats
Dipeptidases  dipeptides into AAs
Pancreas
 Trypsin & Chymotrypsin break down proteins
 Amylase converts starch into maltose
 Lipase breaks fats
Process is complete in about 4 hrs
Pancreas
Secretes
 Hormones
 Sodium
bicarbonate
 Digestive
enzymes
Lipase
Trypsinogen
Amylase
Secretes
 Blood clotting
enzymes
 Stores glycogen
 Bile
Stored in gall
bladder
Emulsifies
fat
Liver
Large Intestine = Colon
1. Anatomy:
2. Functions
a. Reclaim water
b. Synthesis of vitamins by E. coli
Feces
Rectum
Anus
Diarrhea
Constipation
Can you name the parts and tell what
they do?
Food as Fuel
Carbohydrates, fats and proteins are all
used to generate ATP
 Fats9 Calories/gm, Proteins and
Carbs 4Calories/gm
 1 Calorie (kilocalorie)= 1000 calories
 Basic Calorie need 2200 for female
teens, 2500 males
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Accessory Organs
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LIVER
A. Secretions
B. Functions
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1. Digestive function
2. Glycogenesis
3. Gluconeogenesis
4. Glycogenolysis
5. Hematopoiesis in embryo
6. Detoxification
7. Damaged red blood cell
removal
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bile contains pigment byproducts of RBC
bile pigments eliminated from
body with feces
brown feces = rusty iron from
hemoglobin!
Pancreas
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a. Anatomy
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Acinar cells
Islets cells:Alpha, Beta
b. Functions
c. Digestive Enzyme
1. trypsinogen
2. chymotrypsinogen
3. carboxypeptidase
4. aminopeptidase
5. pancreatic amylase
6. pancreatic lipase
These accessory organs secrete their enzymes and a
basic fluid into the duodenum of the small intestine
Figure 41.16 The duodenum
Figure 41.18 Activation of protein-digesting enzymes in the small intestine
Small Intestine
a. Anatomy
1. size
2. villi
3. lacteals
4. glands
b. Functions
c. Secretions
1. mucus
2. maltase
3. sucrase
4. lactase
5. peptidase
6. enterokinase
Figure 41.19 The structure of the small intestine
Absorption in the Small Intestine
villi
microvilli
chylomicrons fats, cholesterol, wrapped in protein
leave cells by exocytosis
lacteals
lymphatic system
hepatic portal vein
MOUTH
What enzymes are made in the pancreas?
STOMACH
SMALL INTESTINE
Hormonal Control
 Enterogastrone
 Gastrin
 Cholecystokinin secreted in
response to the presence of amino acids or
fatty acids, causes the gallbladder to
contract and release bile into the small
intestine and triggers the release of
pancreatic enzymes
 Secretin chyme(acidic pH)enters the
duodenum, signals the pancreas to release
bicarbonate to neutralize the chyme
Flora of Large Intestines
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Living in the large intestine is a rich flora of
mostly harmless bacteria
 Escherichia
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a favorite research organism
 bacteria
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produce vitamins
vitamin K; biotin, folic acid & other B vitamins
 generate
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coli
gases
by-product of bacterial
metabolism
methane, hydrogen sulfide
Large Intestines (colon)
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Reclaiming water
 used
as solvent for various digestive
juices
~7L of fluid secreted into
digestive tract daily
 > 90% of water reabsorbed
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diarrhea = insufficient
water absorbed
 constipation = too much
water absorbed
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Large Intestine Wall
Numerous Goblet Cells
Figure 41.x1 Large intestine
Rectum
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Terminal portion of colon
 Feces
contain
masses of bacteria
 undigested materials, mainly cellulose
 roughage or fiber
 salts

appendix
Structural
Adaptations
reflecting diet have
made mammals very
successful
1. Dentition
Structural Adaptations
2. Length of Digestive
System
Structural Adaptations
3. # of Stomachs
Structural Adaptations
Digesting Cellulose
How well you digest cellulose governs life
strategy of herbivores
COW
Can digest cellulose well; not need to eat
supplemental sugars
GORILLA
Can’t digest cellulose well; must supplement
with sugar sources, like fruit
Figure 5.8 The arrangement of cellulose in plant cell walls
Figure 41.x2 Termite and Trichonympha
Protozoans and Bacteria have enzymes
to digest cellulose