Animal Nutrition
Chapter 41
3 main categories of feeding:
 Herbivores – Plants & algae
 Carnivores – Meat
 Omnivores – Both
3 needs:
 Fuel (ATP)
 Organic matter for
biosynthesis
 Essential nutrients vitamins
Four Main Feeding Mechanisms of Animals
SUSPENSION FEEDERS
SUBSTRATE FEEDERS
Feces
Baleen
Caterpillar
FLUID FEEDERS
BULK FEEDERS
Feeders
 Suspension – Sift food from H20 (strainer)
 Substrate – Live in or on food
 Fluid – Suck nutrients from host
 Bulk – Large pieces
Glucose regulation
 Liver and muscle cells store
energy in the form of glycogen
(extra stored as fat)
 Regulation – Negative feedback
 Thermostat in house
1 When blood glucose
level rises, a gland called
the pancreas secretes insulin,
a hormone, into the blood.
2 Insulin enhances the
transport of glucose into body
cells and stimulates the liver
and muscle cells to store
glucose as glycogen. As a
result, blood glucose level
drops.
STIMULUS:
Blood glucose
level rises
after eating.
Homeostasis:
90 mg glucose/
100 mL blood
4 Glucagon promotes
the breakdown
of glycogen in
the liver and
there lease of
Glucose into the
blood,increasing
blood glucose level.
STIMULUS:
Blood glucose
level drops
below set point.
3 When blood glucose
level drops, the pancreas
secretes the hormone
glucagon, which opposes
the effect of insulin.
41.2 Animal’s diets must supply carbon
skeleton and essential nutrients
 Make Carbohydrates, Proteins and lipids from sugar
and nitrogen.
 Essential nutrients – can’t make must get from food
pre-made
 Amino acids – 20 (meat, cheese, animal products)
 Fatty acids – unsaturated easily attained in diet
 Vitamins – 13 essential – H20 soluble & fat soluble
 C, A, D, E , K
 Minerals - Inorganic nutrients – Calcium,
Phosphate, Iron, Zinc
Obtaining essential nutrients
Essential amino acids from a vegetarian
diet
Essential amino acids for adults
Methionine
Valine
Threonine
Phenylalanine
Leucine
Corn (maize)
and other grains
Isoleucine
Tryptophan
Lysine
Beans
and other
legumes
41.3 Stages of food processing
 Organic material in food – fats,
proteins, and carbohydrates
 Steps of digestion:
 1. Ingestion – Eating
 2. Digestion – Breaking down food
into molecules small enough for
the body to absorb
The four stages of food
processing
Small
molecules
Pieces
of food
Mechanical
digestion
Chemical digestion
(enzymatic hydrolysis)
Nutrient
molecules
enter body
cells
Undigested
material
Food
1 INGESTION
2 DIGESTION
3 ABSORPTION
4 ELIMINATION
 3. Absorption – Cells take up small
molecules
 4. Elimination – Undigested material
passes
Risk of digesting one’s self?
 No – Specialized compartments
 Intracellular – One cell/Sponges
 Extracellular – Breaking down food
outside cells
Digestion in a hydra
Tentacles
Mouth
Food
Gastrovascular
cavity
Epidermis
Mesenchyme
Gastrodermis
Nutritive
muscular
cells
Flagella
Gland cells
Food vacuoles
Mesenchyme
Gastrovascular
Cavity - Sac with a
single opening –
Hydras, Jellies &
flatworms
Variation in alimentary canals
(a) Earthworm. The digestive tract of
an earthworm includes a muscular
pharynx that sucks food in through the
mouth. Food passes through the
esophagus and is stored and moistened
in the crop. The muscular gizzard, which
contains small bits of sand and gravel,
pulverizes the food. Digestion and
absorption occur in the intestine,
which has a dorsal fold, the typhlosole,
that increases the surface area for
nutrient absorption.
Esophagus Crop
Gizzard
Intestine
Pharynx
Anus
Mouth
Typhlosole
Lumen of intestine
(b) Grasshopper. A grasshopper has several
digestive chambers grouped into three
main regions: a foregut, with an esophagus
and crop; a midgut; and a hindgut. Food is
moistened and stored in the crop, but most
digestion occurs in the midgut. Gastric ceca,
pouches extending from the midgut,
absorb nutrients.
Foregut
Midgut
Hindgut
Esophagus
Rectum
Anus
Mouth
Crop
Gastric ceca
Esophagus
(c) Bird. Many birds have three separate chambers—
the crop, stomach, and gizzard—where food is
pulverized and churned before passing into the
intestine. A bird’s crop and gizzard function very
much like those of an earthworm. In most birds,
chemical digestion and absorption of nutrients
occur in the intestine.
Gizzard
Mouth
Intestine
Crop
Stomach
Anus
 Complete digestive system or alimentary
canal
 Nematodes, annelids, mollusks,
arthropods, echinoderms & chordates
 Mouth
 Specialized compartments
Anus
The human digestive system
Salivary
glands
Oral cavity
Parotid gland
Sublingual gland
Esophagus
Pyloric
sphincte
r
Liver
Ascending
portion of
large intestine
Mouth
Pharynx
Esophagus
Submandibular gland
Stomach
Gallbladder
Gallbladder
Liver
Pancreas
Small intestine
Large intestine
Rectum
Appendix
Stomach
Small
intestines
Pancreas
IIeum
of small
intestine
Cecum
Salivary
glands
Cardiac
orifice
Tongue
Anus
Duodenum of
small intestine
Large
intestines
Rectum
Anus
A schematic diagram of
the human digestive system
Peristalsis – rhythmic waves of
contraction and relaxation
 Smooth Muscles pushes the
food along the tract
 Sphincters – Regulate the
passage of material between
chambers (Drawstring)
From mouth to stomach: the swallowing reflex and
esophageal peristalsis
4 The esophageal
sphincter relaxes,
allowing the
bolus to enter the
esophagus.
Epiglottis
up
Bolus of food
Tongue
Glottis
down
and open
Epiglottis
up
Pharynx
Glottis
Larynx
Esophageal
Epiglottis
sphincter
down
contracted
Trachea
To lungs
Esophagus
To stomach
1 When a person is not
swallowing, the esophageal
sphincter muscle is contracted,
the epiglottis is up, and the
glottis is open, allowing air
to flow through the trachea
to the lungs.
Glottis up
and closed
2 The swallowing
reflex is triggered
when a bolus of
food reaches the
pharynx.
Esophageal
sphincter
relaxed 5 After the food
Esophageal
sphincter
contracted
has entered the
esophagus, the
larynx moves
downward and
opens the
breathing
passage.
Relaxed
muscles
Contracted
muscles
3 The larynx, the
upper part of the
6 Waves of muscular
respiratory tract,
contraction
moves upward and
(peristalsis)
tips the epiglottis
move
the bolus
over the glottis,
down
the
esophagus
preventing food
to the stomach.
from entering the
trachea.
Relaxed
muscles
Stomach
Accessory Glands
 Salivary Glands – Deliver saliva with salivary
amylase to begin chemical digestion
 Pancreas – Digestive juices that mix with
chyme in the small intestine
 Liver – Produces bile. Bile salts aid in the
break down of fats
 Gall Bladder – Bile is stored here until needed
The stomach and its secretions
Esophagus
Cardiac orifice
5 µm
Stomach
Interior surface of stomach.
The interior surface of the
stomach wall is highly folded
and dotted with pits leading
into tubular gastric glands.
Gastric gland. The gastric
glands have three types of cells
that secrete different components
of the gastric juice: mucus cells,
chief cells, and parietal cells.
Pyloric
sphincter
Small
intestine
Folds of
epithelial
tissue
Epithelium
3
Pepsinogen
2
HCl
Pepsin (active enzyme)
1
2 HCl converts
pepsinogen to pepsin.
Mucus cells secrete mucus,
which lubricates and protects
the cells lining the stomach.
Chief cells secrete pepsinogen, an inactive form of the
digestive enzyme pepsin.
Parietal cell
Parietal cells secrete
hydrochloric acid (HCl).
1 Pepsinogen and HCI
are secreted into the
lumen of the stomach.
Chief cell
3 Pepsin then activates
more pepsinogen,
starting a chain
reaction. Pepsin
begins the chemical
digestion of proteins.
Stomach
 Stores food and does preliminary
digestion.
 Coating of mucus to not self digest.
 Mixing makes acid chyme. Every 20
seconds due to smooth muscles.
 Pyloric sphincter squirts the acid chyme
to the small intestines. 2 to 6 hours for a
meal to empty.
The duodenum
Liver
Bile
Gallbladder
Stomach
Acid chyme
Intestinal
juice
Pancreatic juice
Pancreas
Duodenum of
small intestine
Flowchart of enzymatic digestion in the human
digestive system
Protein digestion
Carbohydrate digestion
Nucleic acid digestion
Fat digestion
Oral cavity, Polysaccharides Disaccharides
pharynx,
(starch, glycogen) (sucrose, lactose)
esophagus
Salivary amylase
Smaller polysaccharides,
maltose
Stomach
Proteins
Pepsin
Small polypeptides
Lumen of
small intestine
Polysaccharides
Pancreatic amylases
Maltose and other
disaccharides
Polypeptides
Pancreatic trypsin and
chymotrypsin (These proteases
cleave bonds adjacent to certain
amino acids.)
Smaller
polypeptides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Disaccharidases
Dipeptidases, carboxypeptidase, and
aminopeptidase (These proteases split
off one amino acid at a time, working from
opposite ends of a polypeptide.)
Monosaccharides
Amino acids
bile salts prevents small droplets from coalescing into
larger globules, increasing
exposure to lipase.)
Pancreatic lipase
Amino acids
Small peptides
Bile salts
Fat droplets (A coating of
Pancreatic carboxypeptidase
Epithelium
of small
intestine
(brush
border)
Fat globules (Insoluble in
water, fats aggregate as
globules.)
Glycerol, fatty
acids, glycerides
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Nitrogenous bases,
sugars, phosphates
Small Intestine
 Absorption of nutrients takes place
 6 meters
 Duodenum - beginning of S.I.
 Chyme
 Villi – increases SA for more
absorption
The structure of the small intestine
Microvilli
(brush border)
Vein carrying blood to
hepatic portal vessel
Blood
capillaries
Epithelial
cells
Muscle layers
Villi
Epithelial cells
Large
circular
folds
Lacteal
Key
Nutrient
absorption
Intestinal wall
Villi
Lymph
vessel
Large Intestine (Colon)
 Recover water that has entered
the alimentary canal
 Feces (waste) becomes more
solid as it moves through
 Flora of bacteria – E. Coli
 Colon bacteria secrete
methane and hydrogen sulfide
41.5 Modifications
 Teeth – Structural variation
reflecting diets
 Fangs – modified teeth &
unhinged jaw
Dentition and diet
Incisors
Canines
(a) Carnivore
(b) Herbivore
(c) Omnivore
Molars
Premolars
*Stomach – Expandable Carnivores
*Length of alimentary canal –
Herbivores longer
The digestive tracts of a
carnivore (coyote) and
herbivore (koala)
compared
Stomach
Small
intestine
Small intestine
Cecum
Colon
(large
intestine)
Carnivore
Herbivore