Chapter 41
Animal Nutrition
By: Ashley Kelch, Melanie Diaz,
Joy Chao
Overview: The Need to Feed
• Three types of feeders: Herbivores,
Carnivores, and Omnivores
• Three nutritional needs:
– Fuel (chemical energy): For cellular work of
the body
– Organic raw material: For biosynthesis
– Essential nutrients: Like vitamins (animals
cannot make for themselves)
Four feeding mechanisms
• Suspension feeder:
Sift particles in water
(ex. whale)
• Substrate feeder: Live
on food source (ex. fly
larvae)
Feeding mechanisms (cont.)
• Fluid feeder: Suck
nutrient-rich liquid
from host (ex.
mosquito)
• Bulk feeder: Eat
relatively large piece
of food (ex. python)
Glucose Regulation
• Surplus of calories stored as glycogen in
liver and muscle cells
• When glycogen depots are full, calories
stored as fat
• When glycogen needed, taken from depot
and oxidized
Caloric Imbalance
• Undernourishment is when an animal is in
chronic deficit of calories
• Overnourishment, or obesity, contributes
to diabetes, colon and breast cancer, and
cardiovascular disease
Obesity and Evolution
• Natural selection can
sometimes favor
individuals able to
obtain fatty foods
– Petrel parents often
bring their chicks food
rich in lipid so the
chicks can survive if
the parents go hunting
far distances
Essential Nutrients
• Malnourished: lacking one or more
essential nutrients (Undernourished:
lacking in calories)
• Four essential nutrients: Essential amino
acids, Essential fatty acids, Vitamins, and
Minerals
Essential amino acids
• Most common type of malnutrition: protein
deficiency
• Reliable source of essential nutrients: meat, egg,
cheese, and other animal products
• Animal products: “Complete”, has all the
essential amino acids in proper proportions
• Plant products: “Incomplete”, products are deficit
in one or more essential amino acid
Essential fatty acids and Vitamins
• Essential fatty acids
– Animals can synthesize most fatty acids, but need to
obtain some unsaturated fatty acids.
– Used to make phospholipid in membrane
• Vitamins
– Small amount needed
– Split in to water-soluble and fat-soluble
– Water-soluble: includes B complex (coenzyme),
vitamin C (production of connective tissues)
– Fat-soluble: Vitamin A (pigment of the eye), D
(calcium absorption), E (antioxidant), and K (blood
clotting)
Minerals
• Minerals
– Calcium, Phosphorus: construct and
maintains bones
– Iron: component of cytochrome, which is used
in cellular respiration
– Magnesium, iron, zinc, copper, manganese,
selenium, and molybdenium: cofactors of
enzymes
– Sodium, potassium, and chlorine: nerve
functions
Food Processing
• First stage is Ingestion
- the act of eating
• Second stage is Digestion
- breaking down of food into molecules small enough
for the body to absorb
• Third stage is Absorption
- animal’s cells take up small molecules from digestive
compartments
• Fourth stage is Elimination
- undigested material passes out of the digestive
compartment
Digestive Compartments
• These are specialized compartments that help the
animal digest food, but not their own tissue
• Intracellular digestion is when the digestion takes place
inside of the cell: food vacuoles
• Extracellular digestion is when digestion takes place
outside of the cell: gastrovascular cavity (pouch) allows
for digestion of larger prey
• Complete digestive tract (alimentary canal): a digestive
tube with two openings, which carries the food in one
direction
Human Digestive System
• Digestion begins in mouth where saliva is produced to
make food easier to swallow
• The tongue then manipulates the food into a bolus and
pushes into the pharynx (throat)
• The epiglottis then moves to cover the windpipe so that
the food is guided into the esophagus
• The esophagus pushes food to the stomach by
peristalsis (rhythmic waves of contraction)
Human Digestive System cont.
• The stomach can store food and has important digestive
functions
• It secretes gastric juices which are mixed with the food
by the churning of the stomach muscles
• These juices contain hydrochloric acid, which disrupts
the extracellular matrix that binds together the cells in
the food, and pepsin, which breaks peptide bonds,
cleaving them into smaller polypeptides to later be
digested further by the small intestine
• After the food has been sufficiently mixed with gastric
juices it becomes acid chyme, a nutrient- rich broth,
which is slowly passed to the intestine
The Small Intestine
• The small intestine is the longest section of the
alimentary canal
• Acid chyme from the stomach and digestive juices from
the pancreas, liver, and gallbladder mix together in the
first 25cm of the small intestine in a section called the
duodenum
• The Liver produces bile which helps the body digest and
absorb fats
• The Gallbladder stores the bile made in the liver until it is
needed
• The Pancreas produces several hydrolytic enzymes and
a solution rich in bicarbonate that as a buffer to offset the
acidity of chyme coming from the stomach
Small Intestine (cont.)
Small Intestine (cont.)
• Most of the absorption of nutrients in the
alimentary canal takes place in the small
intestine
• The adaptation of folds, villi, and micro villi
greatly increase the surface area for
maximum absorption inside the small
intestine
Small Intestine (cont.)
• Penetrating the core of each villus is a net of
microscopic blood vessels and a small vessel
of the lymphatic system
• Nutrients are absorbed across the epithelial
(intestinal) cells on the outside of each villus
Small Intestine (cont.)
• Some simple sugars are diffused across the epithelial
cells, but most nutrients (amino acids, small peptides,
vitamins, glucose, and several other simple sugars) are
pumped across the membranes
The Large Intestine
• The colon (large intestine) helps to recover
water that has entered the alimentary canal
by absorbing it back into the body.
• Some of the bacteria produce essential
vitamins, including biotin, folic acid, vitamin
K, and several B vitamins. These vitamins,
absorbed into the blood, supplement our
dietary intake of vitamins.
Evolutionary Adaptations
• Mammals have developed adaptations in
their digestive systems specialized for
their diet.
• Many species of bacteria live in the small
intestine of herbivores to help break down
nutrients in plant material that their bodies
have trouble digesting.
Evolutionary Adaptations (cont.)